Advanced Functional Fiber and Smart Textile · Advanced Fiber Materials 1 3 comprehensive reviews provide researchers with a more systematic understanding of the advances in energy

Vol.:(0123456789)1 3

Advanced Fiber Materials (2019) 1:3–31 https://doi.org/10.1007/s42765-019-0002-z

REVIEW

Advanced Functional Fiber and Smart Textile

Qiuwei Shi1,3 · Jianqi Sun1 · Chengyi Hou1 · Yaogang Li2 · Qinghong Zhang2 · Hongzhi Wang1

Received: 15 May 2019 / Accepted: 15 June 2019 / Published online: 2 July 2019 © Donghua University, Shanghai, China 2019

AbstractThe research and applications of fiber materials are directly related to the daily life of social populace and the development of relevant revolutionary manufacturing industry. However, the conventional fibers and fiber products can no longer meet the requirements of automation and intellectualization in modern society, as well as people’s consumption needs in pursuit of smart, avant-grade, fashion and distinctiveness. The advanced fiber-shaped electronics with most desired designability and integration features have been explored and developed intensively during the last few years. The advanced fiber-based products such as wearable electronics and smart clothing can be employed as the second skin to enhance information exchange between humans and the external environment. In this review, the significant progress on flexible fiber-shaped multifunc-tional devices, including fiber-based energy harvesting devices, energy storage devices, chromatic devices, and actuators are discussed. Particularly, the fabrication procedures and application characteristics of multifunctional fiber devices such as fiber-shaped solar cells, lithium-ion batteries, actuators and electrochromic fibers are introduced in detail. Finally, we provide our perspectives on the challenges and future development of functional fiber-shaped devices.

Graphic abstract

Keywords Advanced functional fiber · Energy harvesting · Energy storage · Chromatic fiber · Actuator

Introduction

Clothing is an interactive interface between human and envi-ronment [1]. People usually use different colors and styles of clothing to express and transmit information or adapt to

Qiuwei Shi and Jianqi Sun contributed equally to the work.

Extended author information available on the last page of the article

http://orcid.org/0000-0003-4142-2982

http://crossmark.crossref.org/dialog/?doi=10.1007/s42765-019-0002-z&domain=pdf

4 Advanced Fiber Materials (2019) 1:3–31

1 3

the changes of the external environment [2]. In terms of function and application, clothing can be regarded as the second skin of human beings. With the development of flex-ible electronic technology and the closer interaction between people and the surrounding environment in the information age, smart clothing has gradually entered into people’s hori-zon [3–5]. For example, in science fiction movies, a dress can play music, videos, adjust the temperature, and even surf the internet at the same time. In addition, researchers and fashion design companies also predict the most impor-tant and basic performance of the future smart clothing, including the ability to collect energy, to store energy effi-ciently, to change color controllably, and to change shape at human will [6–9]. If clothing can have both fashion design and the above special functionality, it will be very in line with the future needs of avant-garde consumers. Actually, the high value-added and high-tech integration character-istics of smart clothing have attracted a lot of capital and time investment from high-tech companies and researchers. As-mentioned smart clothing needs the support of flexible, elastic and stretchable electronic devices, especially for the fiber-shaped functional devices. More importantly, fiber is known as the most basic unit of clothing which can be used to design and obtain different patterns and styles of clothing by the weaving and knitting technology. In order to obtain the smart clothing described above with energy collection [10–14], energy storage [15–19], color and shape change, it is necessary to explore multi-functional fibers with such performance.

Figure 1 shows a brief timeline of the developments of manmade fibers. In 1764, the steam-driven Jenny spinning machine was invented and used to transform fibers from natural animals and plants (cotton, hemp, wool fibers, etc.) into longer fibers. Since then, fiber products are beginning to enter people’s lives, and constantly changing the style of

people’s clothing. Following the development of chemistry and the improvement of fiber industry technology, natural and synthetic polymers have been synthesized into chemi-cal fibers [20–22]. The length, thickness, and color of the chemical fibers can be adjusted in the production process. Different types of chemical fibers including cellulose nitrate fiber, viscose fiber, polyamide fiber, and polyester fiber, have the advantages of light resistance, wear resistance, easy drying and mildew resistance, respectively [23–28]. In the information age, the functional fibers have been extensively studied and applied. The functional fibers refer to fibers with special functions including antistatic property, light-guide, ion exchange, thermal insulation, high elasticity, antibacte-rial, flame retardant, and radiation protection [29–31], in addition to their existing properties. The information age has changed these functional fibers from ordinary consuma-bles to high-tech products and has also increased the fierce competition in the fiber industry. Nowadays, with the rise of artificial intelligence technology, researchers believe that fibers should also evolve to intellectualization. However, what should the next generation of fibers be? In response to the performance requirements of smart clothing, advanced fibers with energy collection, energy storage, chromatic-changeable, shape deformable, sensing and biometric characteristics have attracted much attention. In the past five years, various types of advanced fiber-shaped devices including fiber-shaped solar cells, lithium-ion batteries, elec-trochromic devices, and actuators, have been successfully developed [32–45]. To explore the practical possibilities of these smart fiber devices, these fibers have been attempted to weave or weave into textiles, as well as to integrate into clothing [46, 47].

Many researchers have made in-depth comments and reviews on energy harvesting and storage fibers [46–49], and wearable electronics in recent years [50–53]. These

Fig. 1 A brief timeline of the developments of fibers in modern era

5Advanced Fiber Materials (2019) 1:3–31

1 3

comprehensive reviews provide researchers with a more systematic understanding of the advances in energy fib-ers and wearable electronics. However, with the increas-ing demand for smart fiber products and the diversity of application research on functional fibers, the deformable, chromotropic, sensing and antimicrobial fibers have been developed and opened up the research of diversified smart fibers. This review focuses on the significant progress, related challenges, and future perspectives of flexible fiber-shaped multifunctional devices, including fiber-based energy harvesting devices, energy storage devices, chromatic devices, shape deformable devices, as well as the advanced fiber-based integrated textiles and clothes. Particularly, it summarizes fiber-shaped multi-functional devices and their potential applications for portable or wearable functional integrated electronics including newly developed manufacturing techniques and practical functional materials. Fabrication procedures and applica-tion characteristics based on different functional fibers are also discussed. Finally, the remaining problems/chal-lenges and opportunities are then discussed to offer some helpful insights for the practical applications of future fiber-shaped functional devices.

Fiber‑Based Energy Harvesting Devices

For the next coming smart textile, they should be more intel-ligent and independent to achieve their functional versatil-ity. Stem from this purpose, how to realize the self-supply of energy is a vital step that must be taken. In daily life, there are various forms of underutilized energy such as solar energy, kinetic energy of human body and energy loss caused by the difference in temperature. Hence, the energy harvesting devices just like the solar cells, triboelectric nanogenerator and thermoelectric devices emerged as the times require [48].

As the most extensive natural clean energy, the solar energy reveals infinite potential in the fields of energy utili-zation and development. Solar cell is the most effective way to realize photoelectric conversion. Under the illumination condition, the electron–hole pairs generated in the semicon-ductor drift in different directions under the influence of the built-in electric field, forming potential difference and photocurrent between the two poles (Fig. 2a).

In order to gather the kinetic energy, the triboelectric nanogenerators are happened to transfer mechanical energy to electricity as a stylish concept. During the process of periodic contact separation, friction charges are formed on the inner surface of two polymer sheets due to the contact

Fig. 2 Brief schematic diagrams of working mechanism for energy harvesting devices, a solar cells, b triboelectric nanogenerator, and c thermo-electric devices


1 3

electrification effect. Because of the electrostatic induction phenomenon, the corresponding inductive charge will be generated at the conductive material, thus forming an AC signal in the external circuit (Fig. 2b).

Thermoelectric conversion technology based on Seebeck effect has irreplaceable advantages in plenty of dispersed low-grade waste heat conversion power. When there is a temperature difference between the two ends of the material, the carriers inside the material will move from the hot end to the cold end driven by the temperature difference, thus forming a potential difference between the two ends of the material (Fig. 2c).

For the three sorts of emerging energy harvesting devices, their conventional configurations are almost heavy, rigid and limited with a planar structure, which impedes their potential in the fields of wearable technology. In order to be flex-ibly integrated with wearable electronics, the different sorts of efficient fiber-based energy harvesting devices must be explored and developed in the future.

Fiber‑Shaped Solar Cells

As the second layer of human skin that most directly inter-acts with the external environment, the fabrics could protect the body simultaneously absorb the energy from sunlight. Solar cell, a kind of efficient solar energy harvesting device, is regarded as the most promising way to solve energy issues nowadays [49]. Conventional solar cells are almost fabri-cated on the 2D planar rigid substrate thus leads to the fairly limited applied circumstances. Accordingly, the 1D fiber-shaped solar cells are prone to the future application and fac-ile configuration [50]. The combination of 1D fiber-shaped solar cells and natural fabrics could effectively harvest the clean solar energy in outdoor and then instantly power up wearable electronic or reserve the energy into energy stor-age devices.

By substituting the CNT fiber for conventional metal wire as an anode, the mechanical performance of fibrous solar cell presents a marked improvement [52, 53]. In view of this, a sort of double-twisted perovskite solar cell was fabri-cated by a pristine CNT fiber and another CNT fiber that was coated with compact n-TiO2, meso-TiO2, CH3NH3PbI3−xClx, poly(3-hexylthiophene)/single-walled carbon nanotube (P3HT/SWNT), and silver nanowire network from the inside out (Fig. 3a). As shown in Fig. 3b, the double-twisted fibrous perovskite solar cell showed a maximum power conversion efficiency (PCE) of 3.03%, accompanied with Jsc, Voc and FF of 8.75 mA cm−2, 0.615 V and 56.4% respectively. Simi-larly, established on the foundation of intrinsic outstanding electroconductivity and mechanical strength of CNT fiber, a kind of novel CNT fiber electrode consisted of hydrophobic aligned CNT core and hydrophilic aligned CNT sheath was applied on the fibrous dye-sensitized solar cell (DSSC) and

concurrently obtain a supreme PCE of 10%. Based on the composite CNT fiber electrode with the high electrocon-ductivity, mechanical strength and incorporation with other active phases, the assembled fibers only losted 18% of the initial PCE after bending at 90o for 2000 cycles, indicating a promising application regarding flexible wearable electron-ics (Fig. 3c, d). As displayed in Fig. 3e, several fiber-shaped DSSCs could be flexibly woven into the normal textile, meanwhile, there was no fracture and separation under dis-tinct deformations (e.g., bending and twisting). In outdoors, the integrated flexible self-powering device kept a pedom-eter working steadily under sunlight.

Fiber‑Shaped Triboelectric Nanogenerator

In daily life, the human body is performing various actions or motions all the time. Nevertheless, a majority of them are just for coordination of physical moves and superfluous. Tri-boelectric nanogenerators (TENGs) that convert mechanical energy into electricity have received extensive attention owing to its potential as a continuous, self-sufficient and sustained power-supplying source [14, 54]. Benefits from the sensitive sensing of electrical signals for TENGs, it also has broad applications in the fields of sensors or monitors. Recently, due to the rapid development of smart wearable textile, the fibrous TENGs have drawn widespread attention and research.

In order to obtain a fibrous TENG with excellent flex-ibility and stretchability, a highly stretchable sensing fiber with triboelectric sheath-core structure was constructed by a built-in wavy core fiber and intrinsically stretchable sheath tube. The fabrication process and detail structures were shown in Fig. 4a. The core fiber was made of con-ductive metal wire and the wrapped nylon fiber on the out-side surface. For the sheath tube, the silicon rubber grafted by fluoroalkylsilanes (FAS) fiber was wrapped by elastic bamboo fiber which could protected the outer electrode. After the dip-coating of conductive layer silver nanowires (AgNWs) and further spraying of PDMS, the sheath fiber tube presented tensile strain and elastic strain of ~ 600% and ~ 120% respectively. The potential application concern-ing sensor was investigated by a combination between the SSCTEF and a soft knee-pad. As displayed in Fig. 4b, the combined textile responsed to the various motion states which were created by persons with diverse exercising routines. In Fig. 4c, a SSCTEF was fixed with an elbow to simulate a more realistic state of motion. During the pro-cess of bending and straightening, the periodic changes with different output voltage were revealed in that a stream of electrons was induced back and forth between the inner electrode and the electrode of the SSCTEF [55]. The output signal was reflected by joint movements involved stretching, compressing, and bending, which indicating the SSCTEF


1 3

was closer to reality in the motion monitoring compared with traditional sensors.

At present, vast of manufacturing processes of fibrous TENGs are immature and complicated, which hinders the further practical applications and real achievement of e-textile. Hence, it is profound to develop a kind of con-tinuous and large-scale preparation process. Using a modi-fied melt-spinning method, a scalable highly stretchable triboelectric yarn was successfully prepared that based on intrinsically elastic silicone rubber tubes and extrinsically elastic built-in stainless-steel yarns lately [14]. The sketch for the structure and mechanism of SETEY and optical photos of rolled SETEYs were given in Fig. 4d. During the stretching process, in-plane charge separation and alteration of the charge distribution were triggered by the changes of the contact area between the sheath tube and the core yarn, the electrons flow from the ground electrode into the SETEY under the motivation of the increased holes which anchor onto the highly conductive core yarn. The reverse released movement of SETEY drived electrons

flowing back. Thus, the repeated stretching and release of SETEY could obtain an alternating current. Moreover, the water durability of SETEY was also evaluated in this work. Figure 4e depicted the working state and principle of SETEY underneath water. A stable output performance under different depth in water was also observed. The cou-pling effect was created between the surface potential from triboelectrification and induced surrounding bulk water, which greatly promoted the amount of charges generated from SETEY. Even the SETEY was immersed in the water, it still could power up a LCD and the output voltage was not affected by water depth. Figure 4f illustrated the fab-rication of e-textiles based on the SETEY. Double-plied yarn was twisted by commercial stainless-steel yarn and water-resistant modified polyacrylonitrile yarn. Then the composite yarn was weaved with SETEY to form an inte-gral e-textile. The e-textile exhibited exceptional flexibil-ity and stretchability, simultaneously, the self-powering system could harvest biomechanical energy and instantly supply power for portable electronic devices (Fig. 4g).

Fig. 3 a Schematic illustration for the structure of double-twisted fiber-shaped perovskite solar cell. b The J-V curves of the double-twisted perovskite solar cell. a, b Reproduced with permission [51]. Copyright 2015, Wiley–VCH. c Schematics for the fibrous solar cell with the enlarged structure of a CS-CNT electrode fiber by the asym-metrical twisting. d The J-V curve of fibrous solar cell, together with

the power conversion efficiencies of the fiber-shaped solar cell as a function of cycle. e The fiber-shaped solar cells are integrated with fabrics and the combined items could power up pedometer in outdoor. c–e Reproduced with permission [11]. Copyright 2018, The Royal Society of Chemistry


1 3

Fiber‑Shaped Thermo‑Electric Devices

The thermoelectric devices have increasingly attracted extensive attention in which large-area waste heat recov-ery, sensor, heat management of the human body and as a kind of burgeoning energy-harvesting and energy-transfer system [56–59]. Further dimension reduction from bulk or planar thermoelectric functional materials or devices to 1D fiber-shaped configuration could facilitate the scal-able manufacture, lightweight and structural diversification design, meanwhile, the outstanding endurance for intuitive and evident mechanical deformation has been demonstrated by many flexible devices from assembling functional fiber to some extent [60, 61]. Therefore, the fiber-based flexible thermoelectric energy generators are expected to be applied to stable portable energy supply.

Based on the silk yarn with excellent mechanical prop-erties, the outstanding electroconductivity was endowed

by strongly adhering PEDOT:PSS onto the surface of the yarn. The optical photo of comparison with respect to neat and PEDOT:PSS dyed silk yarns were given in Fig. 5a. A uniform blue could be observed on the surfaces of treated silk yarns. In the meantime, the bulk electrical conduc-tivity of silk yarns was significantly increased to a peak at 14 S cm−1 according to log-normal distribution. In Fig. 5b, an in-plane thermoelectric textile integrated with 26 p-type legs was placed upon a reservoir with hot (hot plate) and cold (steel heat sink) temperature ending to test thermoelectric performance. The obtained output voltage of Vout/ΔT ≈ 313 μV K−1 (i.e., 12 μV K−1 for each ele-ment) was relatively close to the speculative value of Vout/ΔT ≈ 351 μV K−1. The ΔT of 66 °C was operated with Rload ranging from 1 to 27 kΩ, hence a current of 1.25 μA and a maximum power output of about 12 nW was measured [62].

The decent mechanical properties could be varied from thermoelectric fibers integrated with textile as shown in

Fig. 4 a Schematic diagram for the fabricating process of a stretch-able sheath-core structural triboelectric fiber (SSCTEF). b The self-powered fabrics weaved by SSCTEF could collect motion signals of different people. c The different voltage signals collected by SSCTEF indicate different states of elbow bending. a–c Reproduced with per-mission [55]. Copyright 2017, Elsevier. d The single electrode tribo-electric yarn (SETEY), the nether digital photos show the scalable SETEYs fabricated by the industrialization process. e Mechanism

illustration of dynamic polarization process when a single SETEY work in water, digital photo shows that the LCD is lit up by the ten-sile of SETEY underneath water, together with the output voltages as a function of different depth underneath water. f Fabrication sketch of the energy textile (e-textile) based on SETEY. g The e-textile displays decent stretchability consequently harvests biomechanical energy to power e-devices handily. d–g Reproduced with permission [14]. Cop-yright 2019, Nature Publishing Group


1 3

Fig. 5c, which a type of intrinsically flexible thermoelectric was fabricated by novel thermal drawing technology. The glass cladding was skillfully loaded onto the thermoelectric core. After the final coating of polymer, the scalable thermo-electric fiber with good flexibility in core-sheath structure was finished. The thermoelectric fibers could be well com-bined with wearable fabrics which are profited by intrinsic flexibility of fibers. Two different thermoelectric devices based on as-prepared thermoelectric fiber were established to examine fiber’s capability of interaction between heat and electricity (Fig. 5d). Under the temperature difference of 19 K, an output voltage of 29 mV was obtained by the cup which was equipped with 7-pair p-n thermoelectric legs.

Moreover, the output voltage and output power density were 97 mV and 2.34 mW cm−2 respectively under a temperature change of 60 K. For another architecture, an output volt-age of 15 mV could be gained by thermoelectric pipe with a temperature difference of 11.4 K. Furthermore, the pipe structure thermoelectric device delivered output voltage of 70 mV and output power density of 1.46 mW cm−2 based on 60 K difference in temperature [61].

Inspired by the concept of through-thickness thermoelec-tric power generation, the thermoelectric textiles were suc-cessfully fabricated by tiger yarns that were combined by separate and alternative n- and p-type segments. The sche-matic illustration for the fabrication of thermoelectric tiger

Fig. 5 a The optical photo of neat and dyed PEDOT:PSS silk yarns, together with the distribution of electrical conductivity of PEDOT:PSS prepared with different solvent. b The in-plane thermo-electric textile integrated with 26 p-type legs is placed between the hot and cold temperature end, the right performance plot presents Vout as a function of ΔT and P, where P = VoutI as a function of measured current I for ΔT = 66 °C. a, b Reproduced with permission [62]. Cop-yright 2017, American Chemical Society. c Schematic diagram for the thermal drawing process of thermoelectric fiber, the as-prepared

fibers in a core-sheath structure show the good flexibility and well integration with textile. d Schematic and demonstration for electricity generation mechanism of the TE-based devices with the correspond-ing voltage and power density evaluated as a function of the ΔT. c, d Reproduced with permission [61]. Copyright 2017, Elsevier. e Sketch of the fabrication process of thermoelectric yarn. f Optical photos for the procedure of tiger TE yarn. g The output power of thermoelectric textile woven by tiger yarns. e–g Reproduced with permission [63]. Copyright 2016, Wiley–VCH


1 3

yarns was shown in Fig. 5e. To start with, the highly aligned sheets of polyacrylonitrile (PAN) nanofibers were gathered onto two parallel wire collectors by electrospinning. Then the thermoelectric active materials were alternately depos-ited on both sides of the as-prepared sheet using a stencil mask. Afterward, the interconnected area between thermo-electric strips was sputtered by gold. Eventually, the thermo-electric tiger yarn was obtained by the further twist of coated yarns. As depicted in Fig. 5f, the initial tiger structure was kept well during the process of twist insertion or subsequent complete yarn untwist. The successive n-p junctions were founded on dense plain-weave thermoelectric textile and the integral textile presents a stable high output power above 0.62 W m−2 and 1.01 µW under the temperature difference of 55 °C (Fig. 5g). In the light of the mentioned three fiber-shaped energy harvesting devices, Table 1 summarized the materials, designing structure, processing techniques, and performances of relevant researches.

Fiber‑Based Energy Storage Devices

With the emergence of a myriad of flexible electronic devices, it is of great concern to search the flexible energy storage devices which are safe, environmental and high- efficient [70, 71]. Nevertheless, the traditional and com-mercially available energy storage devices like lithium-ion battery and supercapacitors, are almost rigid, bulky and in poor adaptability of complicated conditions, which hinder the further development of wearable fields. For being better combined with fabrics or other smart wearable electronic products, bendable, stretchable and deformable fiber-based energy storage devices are expected to be well designed and developed found on these two sorts of energy storage devices.

Fiber‑Shaped Lithium Ion Batteries

Recently, various forms of energy storage devices are exten-sively studied due to their ample storage and lower price. However, they still have a long way off the real world due to their lower output voltage, energy density, higher reactivity, unstable cycling performance, also the premature manufac-turing technique and matching system of electrode/electro-lyte. By comparison, based upon the distinctive properties of lithium metal with high theoretical capacity (~ 3860 mAh g−1) and the lowest electrochemical potential (~ 3.04 V), var-ious lithium-based energy storage systems are boosted to be applied to ubiquitous energy grids [72–74]. Meanwhile, its lower density (~ 0.53 g cm−3) and excellent metal ductility make lithium-based anode be a candidate in more flexible and lighter structures [75–77]. Rechargeable lithium-ion bat-teries (LIBs) have drawn a wide range of research interests

during the past few decades because of their predominant features like long cyclic life-span, high electrochemical win-dow, high energy density, and coulombic efficiency when it comes to those conventional lead-acid and Ni–Cd batteries (Fig. 6a) [78].

In general, the typical structure of LIB consists of elec-trode materials, current collector, separator and electrolyte. Just like the intrinsic mechanism of majority chemical energy storage systems, the lithium ions are deintercalated from cathode to anode via electrolyte in the charging pro-cess. Meanwhile, in order to maintain the charge balance in the system, the electrons flow to the anode by an external circuit. As to the discharging process, the ions and electrons exhibit opposite movement against charging process respec-tively. The LIBs delivery a reversible cycle according to the intercalation/deintercalation of lithium ions (Fig. 6b).

Gradually, in that the demand of human being for energy storage devices is not limited within a fixed location. The structure of the battery is evolving from a three-dimensional bulk to two-dimensional planar structure. Meanwhile, the flexibility and lighter weight of 2D planar configuration greatly excite the potential of the battery in sundry aspects, especially the flexible smart wearable electronics. How-ever, the 2D structure still lacks in the more complicated service environment such as winding, stretching and weav-ing. Except that, the comfort of it just like gas permeability is still to be considered. In view of the mentioned above, it makes sense for researchers to develop lithium-ion batter-ies with 1D fibrous shape, which facilitates the application of energy storage devices in the field of flexible wearable electronics (Fig. 6c).

In order to achieve fibrous structure, one of the most ver-satile approaches is that the mixed active materials, binder and conductive agent slurry are coated or deposited onto the linear current collector. Then the separator with liquid electrolyte/polymer electrolyte are wrapped/dipped onto the electrode. Ultimately, the LIB with typically cable coaxial configuration is fabricated by further winding and sealing. Benefited from the intrinsic advantages of lithium metal, it is also an ideal choice in the 1D lithium-based batteries. Car-bon nanomaterials have great potential as electrode materials and current collectors because of their good electrical con-ductivity, electrochemical stability, and excellent mechanical strength [79]. A sort of composite fiber anodes, combined with aligned multiwalled carbon nanotube (MWCNT) and silicon, and lithium wire were integrated to obtain flexible, wire-shaped lithium-ion battery (Fig. 7a). According to the SEM images (Fig. 7b), the highly aligned MWCNTs fibers showed no obvious aggregates with a uniform Si deposition on the surface, which ensured high tensile strength and elec-trical conductivity. The prepared LIB based on MWCNT/Si composite fiber showed decent specific capacity retention (Fig. 7c).


1 3

Tabl

e 1

Sum

mar

y fo

r mat

eria

ls, d

esig

ning

stru

ctur

e, p

roce

ssin

g te

chni

ques

, and

per

form

ance

s of fi

ber-s

hape

d en

ergy

har

vesti

ng d

evic

es

Fibe

r dev

ice

Mat

eria

lsD

esig

ning

stru

ctur

ePr

oces

sing

tech

niqu

esPe

rform

ance

sRe

fs.

Fibe

r-sha

ped

sola

r cel

lsC

NT

fiber

, CN

T/Ti

O2 c

ompo

site

fib

er (N

719

inco

rpor

ated

)D

oubl

e-tw

isted

Twist

ing

acco

mpa

ny w

ith d

ip-

coat

ing

and

heat

ing

proc

ess

Nor

mal

: PC

E =

2.94

%, fl

exib

le

test:

~ 10

0% P

CE

rete

ntio

n w

ith

the

incr

easi

ng in

cide

nt li

ght a

ngle

fro

m 0

to 1

80°

[52]

Hyd

roph

obic

alig

ned

CN

T, h

ydro

-ph

ilic

alig

ned

CN

T, d

ye-a

bsor

bed

Ti/T

iO2 w

ire

Cor

e–sh

eath

fibr

ous s

truct

ure

Twist

ing

acco

mpa

ny w

ith im

mer

-si

on a

nd h

eatin

g pr

oces

sN

orm

al: P

CE

= 10

.00%

, flex

ible

te

st: ~

86%

PC

E re

tent

ion

at 9

0o fo

r 200

0 cy

cles

[11]

CN

T fib

er, T

iO2,

P3H

T/SW

NT,

Pe

rovs

kite

Dou

ble-

twist

edSp

un-tw

isted

, h e

at-a

ssist

ed c

oat-

ing

Nor

mal

: PC

E =

3.03

%, fl

exib

le

test:

~ 10

0% P

CE

rete

ntio

n af

ter

1000

ben

ding

cyc

les

[51]

Alig

ned

MW

CN

T fib

er, T

iO2

nano

parti

cle

P3H

T:PC

BM

, PE

DO

T:PS

S, T

i wire

Inte

rtwin

ed st

ruct

ure

Post-

proc

essi

ng (h

eat t

reat

men

t, co

atin

g) a

nd tw

istin

gN

orm

al: P

CE

= 1.

78%

, flex

ible

te

st: ~

85%

PC

E re

tent

ion

afte

r 10

00 b

endi

ng c

ycle

s, ~

80%

PC

E re

tent

ion

afte

r 100

0 be

nd-

ing

cycl

es (w

oven

into

flex

ible

su

bstra

te)

[53]

Ti w

ire, T

iO2 c

ompa

ct la

yer,

TiO

2 po

rous

laye

r, pe

rovs

kite

laye

r, Sp

iro-O

MeT

AD

laye

r, th

in g

old

film

Hie

rarc

hica

l ent

angl

ed st

ruct

ure

Spin

coa

ting

toge

ther

with

vap

or-

assi

sted

depo

sitio

n an

d si

nter

ing

in th

e su

bstra

te

Nor

mal

: PC

E =

10.7

9%, fl

exib

le

test:

~ 10

0% P

CE

rete

ntio

n af

ter

500

bend

ing

cycl

es

[64]

Fibe

r-sha

ped

tribo

elec

tric

nano

gen-

erat

ors

Met

al c

ondu

ctiv

e w

ire w

ith n

ylon

fib

er, s

ilico

ne ru

bber

tube

with

FA

S, b

ambo

o fib

er, A

gNW

s, PD

MS

Cor

e-sh

eath

stru

ctur

eC

oilin

g th

e fu

nctio

naliz

ed la

yer

by la

yer

Ultr

ahig

h w

orki

ng st

rain

(100

%),

a m

axim

um se

nsiti

vity

of 1

7.4

per

unit

strai

n

[55]

Silic

one

rubb

er, s

tain

less

-ste

el y

arn

Cor

e-sh

eath

stru

ctur

e (th

e co

re

is e

xtrin

sica

lly e

lasti

c bu

ilt-in

st

ainl

ess-

steel

yar

n)

Con

tinuo

usly

rolli

ng b

y a

spec

ial-

ized

spin

ning

equ

ipm

ent,

toge

ther

w

ith b

low

-mol

ding

and

com

pac-

tion

Scal

able

man

ufac

ture

, lar

ge

wor

king

stra

in (2

00%

), su

perio

r pe

rform

ance

in li

quid

, all-

wea

ther

du

rabi

lity

[65]

Silic

one

rubb

er, c

ondu

ctiv

e ya

rnC

oaxi

al c

ore-

shea

th st

ruct

ure

Win

ding

the

inte

rnal

cor

e an

d ex

tern

al sh

eath

resp

ectiv

ely

and

inse

rting

them

Exte

nsiv

e m

ulti-

scen

ario

app

lica-

tion

(suc

h as

ges

ture

-rec

ogni

zing

, la

rge-

area

ene

rgy-

harv

estin

g an

d su

stai

nabl

y ch

argi

ng)

[66]

PDM

S, C

NT,

PM

MA

Hie

rarc

hica

l Coa

xial

stru

ctur

eW

rapp

ing

and

dip-

coat

ing

alon

g w

ith p

re-s

tretc

h op

erat

ion

Flex

ible

, stre

tcha

ble,

wea

vabl

e,

conv

ertin

g m

ultid

irect

iona

l m

echa

nica

l ene

rgie

s to

elec

tric-

ity, s

ensi

ng d

iver

se m

echa

nica

l sti

mul

i

[67]

AgN

Ws,

PTFE

, PU

, PD

MS-

AgN

W

film

Coa

xial

cor

e-sh

eath

stru

ctur

eC

ompr

isin

g w

rapp

ing

and

coat

ing

A m

axim

um p

eak

pow

er d

ensi

ty

of 2

.25

nW c

m−

2 with

relia

ble

dura

bilit

y (4

000

testi

ng c

ycle

s),

vers

atile

phy

siol

ogic

al si

gnal

s m

onito

ring

[68]


1 3

Tabl

e 1

(con

tinue

d)

Fibe

r dev

ice

Mat

eria

lsD

esig

ning

stru

ctur

ePr

oces

sing

tech

niqu

esPe

rform

ance

sRe

fs.

Stai

nles

s-ste

el fi

bers

, die

lect

ric

fiber

sC

ore–

shel

l stru

ctur

eC

over

ing

fiber

s are

twin

ed a

roun

d co

re fi

bers

to fa

bric

ate

core

–she

ll ya

rns

Scal

ed-u

p fo

r fab

ricat

ion,

mac

hine

w

ashi

ng u

p to

120

tim

esC

an b

e fu

rther

pro

cess

ed b

y cu

tting

an

d se

win

g fo

r gar

men

t des

ign,

hi

gher

or c

ompa

rabl

e ou

tput

vol

t-ag

e/cu

rren

t.

[9]

Stai

nles

s ste

el, p

olye

ster fi

ber,

PDM

SH

iera

rchi

cal c

ore-

shea

th st

ruct

ure

Twist

ed in

ner s

truct

ure

with

PD

MS

prot

ectio

nTh

e m

axim

um p

eak

pow

er d

ensi

ty

of 3

D te

xtile

(wov

en b

y en

ergy

-ha

rves

ting

yarn

) can

reac

h 26

3.36

m

W m

−2 u

nder

the

tapp

ing

freq

uenc

y of

3 H

z, la

rge-

area

en

ergy

-har

vesti

ng a

nd su

stai

nabl

y ch

argi

ng, m

onito

ring

the

mov

e-m

ent s

igna

ls

[69]

Fibe

r-sha

ped

ther

mo-

elec

tric

devi

ces

Dye

ing

silk

(fro

m B

omby

x m

ori),

PE

DO

T:PS

SC

ore–

shel

l stru

ctur

eD

ip-c

oatin

g w

ith d

yein

g pr

oces

sB

ulk

elec

trica

l con

duct

ivity

of 1

4 S

cm−

1 , hig

h Yo

ung’

s mod

ulus

of

appr

oxim

atel

y 2

GPa

, sca

led

up

to 4

0 m

long

[62]

Bi 0.

5Sb 1

.5Te

3, B

i 2Se 3

, bor

osili

cate

gl

ass

Cor

e-sh

eath

stru

ctur

eTh

erm

al d

raw

ing

tech

nolo

gy (m

elt-

ing

spin

ning

)O

utpu

t vol

tage

and

pow

er d

ensi

ty

are

97 m

V a

nd 2

.34

mW

cm

−2

(ΔT

= 60

K, 7

-pai

r p-n

legs

), ou

tput

vol

tage

and

pow

er d

ensi

ty

are

70 m

V a

nd 1

.46

mW

cm

−2

(ΔT

= 60

K, 5

-pai

r p-n

legs

)

[61]

Bi 2T

e 3, S

b 2Te

3, PA

N, A

uC

ompo

site

d hi

erar

chic

al tw

isted

ya

rn st

ruct

ure

Elec

trosp

inni

ng, t

oget

her w

ith

depo

sitin

g by

sten

cil-m

ask,

and

po

st-tw

istin

g pr

oces

s

Nan

ofibe

r: ZT

Sb2T

e3/P

AN

= 0.

48ZT

Bi2

Te3/

PAN

= 0.

14Ya

rn: Z

T Sb2

Te3/

PAN

= 0.

24ZT

Bi2

Te3/

PAN

= 0.

07O

utpu

t pow

er is

8.5

6 W

cm

−2

(ΔT

= 20

0 K

)

[63]

CN

T ca

rbon

nan

otub

e, N

719

cis-

diis

othi

ocya

nato

-bis

(2,2′-b

ipyr

idyl

-4,4′-d

icar

boxy

lato

) rut

heni

um(II

) bis

(tet

rabu

tyla

mm

oniu

m),

PCE

pow

er c

onve

rsio

n effi

cien

cy, P

3HT

poly

(3-h

exyl

thio

phen

e),

P3H

T:PC

BM p

oly(

3-he

xylth

ioph

ene)

:phe

nyl-C

61-b

utyr

ic a

cid

met

hyl e

ster,

PED

OT:

PSS

poly

(3,4

-eth

ylen

edio

xyth

ioph

ene)

:pol

y(sty

rene

sulfo

nate

), FA

S flu

oroa

lkyl

sila

nes,

AgN

Ws s

ilver

nan

ow-

ires,

PDM

S po

lydi

met

hyls

iloxa

ne, P

MM

A po

lym

ethy

l met

hacr

ylat

e, P

TFE

poly

tetra

fluor

oeth

ylen

e, P

U p

olyu

reth

ane,

PAN

pol

yacr

ylon

itrile


1 3

The lithium–sulfur battery system exhibits a promising future in energy storage due to a high theoretical energy density of 2600 Wh kg−1 and the lower the cost of sulfur cathode. In view of this, a 1D cable-shaped lithium–sulfur battery was fabricated by wire-shaped composite cathode and lithium wire anode (Fig. 7d). A hybrid fiber consisting of aligned CNT fibers and sulfur worked as cathode. The lithium wire acted as anode. The assembled fiber-shaped Li–S battery was able to light up a red light-emitting diode (LED) (ignition voltage of ≈ 1.8 V). Meanwhile, it could be integrated into the fabric cloth and power the LEDs instantly (Fig. 7e). In a rate range from 0.1 to 1 C, the energy density of fiber-shaped lithium–sulfur battery could peer with pla-nar lithium–sulfur batteries yet overwhelms flexible lithium-ion batteries and supercapacitors, which was advantageous to practical application in flexible energy storage devices (Fig. 7f). In order to meet more versatile applications, a kind of stretchable lithium metal battery was fabricated on the elastic fiber by the structural design of electrode (Fig. 7g). The 1D stretchable lithium metal battery showed a hierarchi-cal ring structure and decent flexibility (Fig. 7h). Although the stretchable fiber-shaped battery with a series strain state of 0, 25, 50, 75, and 100%, it showed a negligible capacity loss in the in situ discharge/charge profiles, emphasizing the desired promising application of stretchable battery (Fig. 7i).

For now, the mentioned fiber shaped LIB involved with lithium wire is still in its infancy because of the inevitable safety issues, just like the metallic activity and sensitivity of lithium to oxygen and humidity. Moreover, it is better to introduce safe electrolyte or solid electrolyte for the sake of wearable application [83, 84]. Inspired by the emerging and efficient manufacturing process, as shown in Fig. 8a, an all-fiber LIB were fabricated by 3D printing technol-ogy. The electrode materials, lithium iron phosphate (LFP) and lithium titanium oxide (LTO), were mixed with carbon nanotubes and polymer to obtain highly viscous printable inks. Both as-printed fiber electrodes demonstrated good flexibility and electrochemical performance. All-fiber LIB was assembled by twisting the as-printed LFP and LTO fibers electrodes together with gel polymer electrolyte. As shown in Fig. 8b, the all-fiber device could light up a LED at straight or bending states without brightness failure, because of the good flexibility and proper mechanical strength of as-printed electrode fibers. They could be easily woven into fabrics as well. The initial charge and discharge capaci-ties were about 141.3 and 110 mAh g−1 respectively, with Coulombic efficiency of 77.1%. The charge and discharge capacities gradually stabilized at 91.7 and 89 mAh g−1 with a high capacity retention of 81% after 30 cycles (Fig. 8c).

Nowadays, the f lexible power devices require not only the improvement for high energy density and power density, but also the safety and flexibility for practical application. Thus, it is particularly important to develop

the energy storage devices that can work under some sud-den conditions. Figure 8d presented the diagrams of the manufacturing steps for fibrous electrodes and the assem-bly process of a kind of self-healable fiber-shaped LIB. The self-healing property was mainly attributed to the abundant hydrogen bonds in the supramolecular network at the broken surface. The stress induced by the recov-ery of the PU will pull the disconnected rGO fiber to the interconnected state [85]. In Fig. 8e, the fiber-shaped LIB could power up LED display board under various states. The batteries could also be successfully weaved into textile. The fair cycling performance of self-healable fiber-shaped LIB indicated the potential application in wearable electronics (Fig. 8f). Based on multilayered coaxial structure, Fig. 8g showed a kind of all-solid-state flexible 1D LIB. The micro coaxial batteries over the CF surface were fabricated via electrophoretic deposition and dip-coating methods. After charging at appropriate current density, a red LED could be driven by the micro-coaxial battery at ordinary and knotting states (Fig. 8h). On the premise of excellent flexibility, the microfiber battery also exhibited a stable potential window of 2.5 V and retains up to 85% discharge capacity even after 100 charge/discharge cycles (Fig. 8i).

The progress on 1D fiber-shaped LIBs study is excit-ing. Nevertheless, the considerable efforts with aspect to energy density, the endurance of water or other more complicated application conditions and industrialized manufacture still need to be paid in the future work.

Fiber‑Shaped Supercapacitor

Different from the conventional capacitors and commercial LIBs, supercapacitors (SCs), also known as ultracapacitors, are promising energy storage devices that can be safely charged/discharged within seconds, simultaneously accom-panied with extremely long cycle life (more than 100,000 cycles). Combined with the properties of high-power den-sity (often more than 10,000 W kg−1) and simple structures, SCs are developing into one of most potential candidates for future wearable electronic devices [88–90].

To be closer to the practical operation of wearable fabrics device, the common planar sandwich structures of SCs is necessary to evolve into the fibrous configuration [91]. 1D fiber-shaped SCs are usually miniaturized with diameters ranging from micrometers to millimeters. Their smaller size, lighter weight, and unique wire-shaped structure properties allow them to be various desired shapes and woven or knit-ted into fabrics. The low dimensional carbon-based materials are also suitable for the electrodes of SCs because of excel-lent electronic conductivity, high theoretical specific capac-ity, and outstanding electrochemical stability [92]. Utilizing the excellent intrinsic properties of graphene, the porous


1 3

graphene ribbons were prepared by spinning composite graphene oxide supramolecular hydrogel, directly reducing and removing the additive (Fig. 9a). The high-performance yarn SC was fabricated by the combination of 1D porous graphene ribbons and gel electrolyte. The wrinkles and pores could be easily observed in this porous graphene ribbons with novel structure, which was appropriate to be integrated or woven into textile (Fig. 9b). As depicted in Fig. 9c, the yarn SC was weaved into a glove and there was only 5% capacitance loss after 100 bending cycles which demonstrate an ideal electrochemical and mechanical stability. Recently, a kind of hybrid fiber consist of graphene oxide and cel-lulose nanocrystal was prepared through non-liquid–crystal spinning and following reducing treatment (Fig. 9d). The obtained hybrid GO/CNC fibers exhibited unobstructed channels for the transfer of carriers which ensured the fur-ther electrochemical performance for the whole device. The capacitance retention was around 100% although under dif-ferent bending angles (Fig. 9e). Meanwhile, the capacitance could remained about 97.2% after 500 cycles at a 180° bend-ing angle, which indicated a foreseeable operationality for flexible electronics.

In some special cases, the multifunctionality of single parts will significantly promote the environmental adapt-ability of the whole device. For instance, the colorful fluo-rescent fiber-shaped supercapacitors with several different colors from red to purple were fabricated by introducing the fluorescent dye particles on top of the surface of aligned multiwalled carbon nanotubes (Fig. 9f). The colorful fibrous

supercapacitors made up of fluorescent fiber electrode are well integrated with fabrics. Besides, the multicolor improve the visibility so that play a warning role in the darkness (Fig. 9g). Moreover, according to Fig. 9h, the working stabil-ity of fluorescent supercapacitors on energy storage predict satisfactory practicability in real life.

Stretchability is also an important index to evaluate flex-ible energy storage devices, the textile with better stretch-ability has greater deformation potential. Lately, the stretch-able all-gel-state fibrous supercapacitor was established by 3D hybrid hydrogel found on concept of all-hydrogel design [96]. Figure 10a presented the fabrication process of hybrid hydrogel fibers and all-hydrogel-state fiber devices. The hybrid hydrogel was formed by immediately mixing GO and PANI dispersion solution. The hydrogel was molded into fiber shape after further reduction and then assembled to form a device. Due to the outstanding flexibility of hybrid fiber electrode, a spring-like SC was prepared by structural design. The good capacitance retention of the spring-like SC was achieved under various elastic changes and long tensile cycles (Fig. 10b). The 86% capacitance retention of hybrid fiber could be observed in Fig. 10c after 17000 cycles, indicating the eminent stability. Back to practical reality, continuous and scalable preparation of the high-per-formance materials are profound. In Fig. 10d, the ultralong MoS2 modified rGO fibers (rGMF) were fabricated by a fac-ile wet-spinning method. The addition of MoS2 nanosheets increases active sites and simultaneously keeps the wrinkle structure of rGO thus lead to a high capacitance. In this case,

Fig. 6 a The comparison of the different kinds of batteries in the light of volumetric and gravimetric energy density. Reproduced with permission [78]. Copyright 2001, Nature Publishing Group. b Typical structure of the lithium-ion bat-tery and the transport direction of ions during the charging/dis-charging process. c The possible evolution process about the configuration of batteries


1 3

an all-solid-state fiber-shaped supercapacitor was designed by the combination of rGMFs and PVA-H3PO4 gel elec-trolyte. The device could be woven into fabrics and textile with decent electrochemical stability under bending states (Fig. 10e). Next to the above topic, using MnO2 core–shell nanorod and MoO2@C nanofilm as positive and negative

electrode respectively, PVA-LiCl gel acted as the electrolyte, a kind of wire-type asymmetric pseudocapacitor has been fabricated. Because of the simple configuration, it thus could be easily scaled up to 100 cm in length. At the same time, the device exhibits fair flexibility and stable power output (Fig. 10f). Likewise, the pseudocapacitor gives expression

Fig. 7 a Schematic illustration of fiber-shaped LIB made up with MWCNT/Si composite fiber and lithium wire. b SEM images regard-ing the aligned MWCNTs fibers and composite fiber electrode. c Variation of specific capacity with the cycle number. a–c Reproduced with permission [80]. Copyright 2014, Wiley–VCH. d Schematic illustration and digital photos of 1D cable lithium–sulfur battery. e The open circuit voltages of cable lithium–sulfur battery at differ-ent bending angles and the LED can be lighted up at different situa-tions. f Comparison between cable lithium–sulfur battery with other

kinds of energy storage devices on energy density. d–f Reproduced with permission [81]. Copyright 2015, Wiley–VCH. g Schematically showing the fabricated process of stretchable fiber-like lithium metal battery. h The inner structure of stretchable fiber-like lithium metal battery and flexibility representation. i Charge and discharge profiles with the strain being increased from 0, 25, 50, and 75% to 100% at the current density of 50 mA g−1. g–i Reproduced with permission [82]. Copyright 2019, Elsevier


1 3

to an outstanding cyclic stability with 97.36% capacitance retention of initial state after 100,000 times [97]. As shown in Fig. 10g, there was no obvious capacitance loss after bending and recovery.

Table 2 lays down a set of guidelines considering the important parameters with regards to fiber-shaped energy storage devices research. The state-of-the-art works have performed well on the aspect of safety, energy density, out-put voltage, cycling performance under normal or compli-cated states, flexibility, weather durability, and scaled-up manufacturing etc. [98–102]. Nevertheless, the restriction about integrity of those single excellent performance still hinder the practical utilization and commercialization. The comprehensive concerns should be well considered in the next future development [103].

Fiber‑Shaped Chromatic Devices

Color is very important to nature and human society. Peo-ple can design brilliant and colorful patterns and styles to express their emotions and stories through simple and imaginative combinations of colors. In recent years, with the rapid development of flexible electronic materials and wearable products, high flexible, portable, intelligent and multi-functional equipment has become a hot spot of con-sumption growth. Decorations and clothes with constant color can no longer meet people’s demand for fashion and novelty. Therefore, flexible intelligent chromatic materials and devices have become a hot topic and have been widely studied. According to the different physical or chemi-cal mechanisms, chromatic devices can be divided into electrochromic, thermochromic and structurally colored devices [33, 34, 113]. This section will introduce the lat-est research progress of fiber-shaped chromatic devices.

Fig. 8 a Schematic fabrication process of all-fiber LIB by 3D print-ing. b Display of the all-fiber battery lighting up a red LED in the straight and bending state. c Cycling performance of 3D printed all-fiber device. a–c Reproduced with permission [86]. Copyright 2017, Wiley–VCH. d Schematic illustration of preparation for fibrous elec-trodes and the assembly process of the LIB. e Digital photos of an all-fiber quasi-solid-state with good integration for fabrics. f Cycling

performance at different working states. d–f Reproduced with per-mission [85]. Copyright 2018, Elsevier. g Schematic of all-solid-state flexible LIB. h A yellow LED can be lighted up by cable type all-solid-state LIB at normal and knitting states. i The cyclic capac-ity retention of all-solid-state flexible LIB for 100 cycles. g–i Repro-duced with permission [87]. Copyright 2019, American Chemical Society


1 3

Electrochromic Fibers

The sandwich-like structure is considered to be a typical structure of electrochromic devices, which consists of two transparent conductive electrodes with an internal elec-trochromic active layer [114, 115]. There are two kinds of electrochromic active layers for different electrochromic materials. One is the mixed structure of electrochromic materials and electrolytes. The other is the layered structure of electrochromic materials, electrolytes, and electrodes. However, a series of problems are encountered in the prep-aration of electrochromic fibers, including the difficulty of

miniaturization of electrodes, the uneven distribution of the electric field, and the poor stability during a small curvature radius. Nevertheless, efforts have been made to fabricate electrochromic fibers by spirally rolling the narrow elec-trochromic films, paralleling the coil electrode on a fiber substrate, and wrapping fiber electrode on a fiber device [32, 35, 116].

Current electrochromic fibers include three typical struc-tures: coiled, helically coaxial and wrapped structures. A stretchable coiled electrochromic fiber with display com-ponents was made with three main parts [116]. First, the electrochromic bands were prepared on the thin plastic

Fig. 9 a Schematics for the formation of porous graphene ribbons and all-solid-state yarn supercapacitor. b SEM images of porous graphene ribbons and yarn SC. c Flexible and cyclic valuation and of yarn supercapacitor woven into a glove. a–c Reproduced with per-mission [93]. Copyright 2015, Elsevier. d Schematic illustration con-cerning the preparation of rGO/CNC composite fiber. (Inserts is the ross-section SEM image of rGO/CNC-20 hybrid fiber). e Stability study of the device at various bending states. d, e Reproduced with

permission [94]. Copyright 2018, Elsevier. f Schematics of the fab-rication process of fluorescent hybrid fibers and the digital photos of multicolor fiber electrodes. g Photographs of the integration between fluorescent fibrous supercapacitors and fabric. h Cycling performance of fluorescent supercapacitor fiber and inset is spectrum before and after cycles. f–h Reproduced with permission [95]. Copyright 2017, Wiley–VCH


1 3

membrane by patterning the electrochromic active materi-als of PEDOT:PSS and insulation layer of cytop, and then casting ionic liquid and PVDF-HFP based solid electrolyte. Second, the thread shape of display elements was formed through the slit and release of fabricated electrochromic bands. Finally, the stretchable electrochromic fiber was obtained by helically rolling the slit films around polyu-rethane rubber. The extensibility of the fabricated coiled electrochromic fiber was demonstrated. 4 pixels were con-tained in one fiber device. The pitch angle of the yarn was 45 degree. The selected one pixel changed its color form pale to dark blue through the voltage application. However, this kind of fiber-shaped electrochromic devices was relatively

large and exhibited monotonous color, and could not effec-tively meet the requirements regarding weavability.

In order to improve the practicability of electrochromic fibers, Lin et al. prepared a multicolor electrochromic fiber which shows red, green, and gold, turning by the applied voltages [35]. As shown in Fig. 11a, the multicolor elec-trochromic fiber was prepared by a template method. WO3 and poly(3-methylthiophene) were used as electrochromic active substances, and they were selectively deposited onto the electrodes. Figure 11b exhibited digital pictures of the coloration and discoloration of the fiber. The color of cath-ode changed to dark green when a +1.5 V bias was applied. When a − 1.5 V reverse bias was applied, the colors of two electrodes exchanged. Figure 11c displayed the reflectance

Fig. 10 a Schematic for the formation of PANI/GO hybrid hydrogels. b The variation of capacitance retention under stretching/compress-ing states and cyclic stretch, this kind of stretchable SC can be well woven into yarn to power up LEDs. c Cyclic stability of SC at a cur-rent density of 1.26 A g−1. a–c Reproduced with permission [96]. Copyright 2018, Wiley–VCH. d Schematic diagram for the forma-tion of hybrid fiber electrode, together with the SEM images of it. e

The flexibility and weavability displays of fibrous all-solid-state SCs. d, e Reproduced with permission [17]. Copyright 2019, The Royal Society of Chemistry. f Schematic for the structure of asymmetric pseudocapacitor, a scalable spring-like device could light up an LED display board. g Electrochemical stability was proved under various deformed states. f, g Reproduced with permission [97]. Copyright 2019, Wiley–VCH


1 3

Tabl

e 2

Sum

mar

y fo

r con

figur

atio

n, d

evic

e ca

paci

ty, c

yclin

g re

tent

ion,

and

flex

ibili

ty o

f fibe

r-sha

ped

ener

gy st

orag

e de

vice

s

Fibe

r dev

ice

Con

figur

atio

n (c

atho

de//a

node

el

ectro

lyte

)D

evic

e ca

paci

tyC

yclin

g re

tent

ion

Flex

ibili

tyRe

fs.

Fibe

r-sha

ped

lithi

um io

n ba

ttery

MW

CN

T/M

nO2 fi

ber//

Li w

ire10

9.62

mA

h cm

−3 o

r 218

.32

mA

h g−

1 @5 ×

10−

4 mA

[104

]

CN

T@α-

Si c

ompo

site

yar

ns//L

i m

etal

2200

mA

h g−

1 @0.

2C86

% a

fter 3

0th

[105

]

Alig

ned

MW

CN

T/Si

com

posi

te

fiber

//Li w

ire16

70 m

Ah

g−1 @

1A g

−1

1042

mA

h g−

1 @3A

g−

158

% a

fter 5

0th

(1A

g−

1 )A

fter 1

00 c

ycle

s ben

ding

, 80%

ca

paci

ty a

fter 2

0th

@2A

g−

1[8

0]

CN

T-LM

O c

ompo

site

yar

n//C

NT-

Si/C

NT

com

posi

te y

arn

106.

5 m

Ah

g−1 @

1C87

% a

fter 1

00th

Wov

en in

to fa

bric

s and

wor

king

no

rmal

ly[1

06]

MW

CN

T/LM

O c

ompo

site

fibe

r//M

WC

NT/

LTO

com

posi

te fi

ber

91.3

mA

h g−

1 @0.

1 m

A c

m−

195

% a

fter 5

0th

78%

afte

r 100

th92

% c

apac

ity re

tent

ion

@18

0o ben

d-in

g, >

88%

cap

acity

rete

ntio

n @

strai

n of

600

%

[107

]

Alig

ned

CN

T/G

O/C

MK

-3@

S//L

i w

ire10

51 m

Ah

g−1 @

0.1C

(coi

n ty

ped)

~100

0 W

h kg

−1 @

0.1C

(cab

le

lithi

um–s

ulfu

r bat

tery

)

600

mA

h g−

1 reta

ined

afte

r 100

th

(coi

n ty

ped)

Nor

mal

ly w

ork

@18

0o ben

ding

[81]

3D p

rinte

d LF

P//3

D p

rinte

d LT

O~1

10 m

Ah

g−1 @

50 m

A g

−1

81%

afte

r 30t

hN

o fa

ilure

of t

he L

ED b

right

ness

at

bend

ing

[86]

LCO

nan

opar

ticle

s@ rG

O//S

nO2

quan

tum

dot

s@rG

O10

1.1

mA

h g−

1 @0.

1A g

−1

~80%

afte

r 50t

h82

.2%

cap

acity

rete

ntio

n af

ter 5

0 cy

cles

@ b

endi

ng a

nd tw

istin

g[8

5]

MoS

2@C

NT

fiber

//Li-Z

nO@

CN

T fib

er11

69 m

Ah

g−1 @

50 m

A g

−1

96%

afte

r 100

th90

.3%

cap

acity

rete

ntio

n at

a st

rain

of

100

% fo

r 100

tim

es[8

2]

LFP

@ca

rbon

fibe

r//LT

O4.

2 μA

h cm

−2 @

13μA

cm

−2

85%

afte

r 100

thN

orm

ally

wor

k un

der m

ultip

le

bend

ing

stat

es[8

7]

Fibe

r-sha

ped

supe

r cap

acito

rB

iscr

olle

d PE

DO

T/M

WN

T ya

rn/P

t w

ire (P

VA/H

2SO

4 sol

id e

lect

ro-

lyte

)

~179

F c

m−

3 @0.

01 V

s−1

99%

afte

r 10,

000t

h (s

ewed

into

gl

oves

)92

% a

fter 1

0,00

0th

@be

ndin

g99

% a

fter 1

0,00

0th

@se

win

g[1

08]

NiC

o 2O

4 nan

oshe

ets/

stai

nles

s-ste

el

wire

(PVA

/KO

H g

el e

lect

roly

te)

10.3

F c

m−

3 @ 0

.08

mA

78%

afte

r 500

0th

~ 90

% c

apac

itanc

e re

tent

ion

afte

r 50

0 cy

cles

ben

ding

[109

]

Poro

us g

raph

ene

ribbo

ns (H

3PO

4/PV

A g

el e

lect

roly

tes)

208.

7 F

g−1 @

0.1

A g

−1

99%

afte

r 500

0th

> 9

5% c

apac

itanc

e re

tent

ion

afte

r 10

0 cy

cles

ben

ding

[93]

Bis

crol

led

MnO

2/CN

T ya

rns (

PVA

/Li

Cl g

el e

lect

roly

te)

166

F g−

1 @2.

3 m

A c

m−

2

C A =

889

mF

cm−

2

CV

= 15

5 F

cm−

3

E A =

35.8

μW

cm

−2

E V =

5.41

mW

h cm

−3

92%

afte

r 100

0th

~ 10

0% c

apac

itanc

e re

tent

ion

afte

r 10

00 b

endi

ng c

ycle

s fro

m 0

° to

165°

[110

]

rGO

nan

oshe

ets/

stai

nles

s-ste

el w

ire

(PVA

/H3P

O4/N

a 2M

oO4 p

olym

er

gel e

lect

roly

te)

18.7

5 m

F cm

−1 (C

A =

38.2

mF

cm−

2 ) and

2.6

mW

h cm

−1

(EA

= 5.

3 m

Wh

cm−

2 ) @0.

5 m

A

~ 10

0% a

fter 2

500t

h~

100%

leng

th c

apac

itanc

e re

tent

ion

unde

r diff

eren

t ben

ding

con

ditio

ns[1

11]

Pt/C

NT@

PAN

I com

posi

te y

arn

(PVA

/H3P

O4 g

el e

lect

roly

te)

C A =

91.6

7 m

F cm

−2

E A =

12.6

8 m

Wh

cm−

2

@0.

8 m

A c

m−

2

80%

afte

r 500

0th

Neg

ligib

le lo

ss o

f cap

acita

nce

at

diffe

rent

ben

ding

ang

les f

rom

0°

to 1

80°

[112

]


1 3

Tabl

e 2

(con

tinue

d)

Fibe

r dev

ice

Con

figur

atio

n (c

atho

de//a

node

el

ectro

lyte

)D

evic

e ca

paci

tyC

yclin

g re

tent

ion

Flex

ibili

tyRe

fs.

Hyb

rid G

O/C

NC

fibe

rs (P

VA/

H2S

O4 g

el e

lect

roly

te)

123.

2 F

g−1 (C

V =

155.

8 F

cm−

3 E V

= 5.

1 m

Wh

cm−

3 ) @0.

1 A

g−

192

.1%

afte

r 100

0th

97.2

% c

apac

itanc

e re

tent

ion

afte

r be

ndin

g at

180

o for 5

00 ti

mes

[94]

PAN

I/rG

O fi

bers

(PVA

/H2S

O4 g

el

elec

troly

te)

E V =

8.80

mW

h cm

−3

P V =

30.7

7 m

W c

m−

386

% a

fter 1

7,00

0th

Subt

le c

apac

itanc

e lo

ss d

urin

g th

e str

etch

ing

proc

ess

[96]

Fluo

resc

ent h

ybrid

MW

CN

T fib

erC

V =

11.9

8 F

cm−

3 @ 1

0 m

A c

m−

398

.4%

afte

r 10,

000t

hSt

able

col

or in

tens

ity m

aint

aine

d,

acco

mpa

nied

by

stab

le sp

ecifi

c ca

paci

tanc

e w

ith li

ttle

varia

tion

[95]

MnO

2 cor

e–sh

ell n

anor

od a

rray

//M

oO2@

C n

anofi

lm (P

VA/L

iCl g

el

elec

troly

te)

C A =

31.7

mF

cm−

2

CV

= 13

.45

F cm

−3

E V =

9.53

mW

h cm

−3

P V =

2272

0 m

W c

m−

3

~97.

36%

afte

r 100

,000

thSc

aled

up

to 1

m w

ith g

ood

flex-

ibili

ty (c

an b

e re

adily

ben

t with

di

ffere

nt d

egre

es fr

om0°

to 3

60°)

[97]

NaD

C/rG

O/M

oS2 h

ybrid

fibe

r (P

VA/H

3PO

4 gel

ele

ctro

lyte

)13

4.38

F g

−1 (C

A =

332.

85 m

F cm

−2

CV

= 21

.9 F

cm

−3 ) @

50

mA

~73%

afte

r 800

th (t

este

d w

ith th

e be

ndin

g pr

oces

s)~

73%

cap

acita

nce

rete

ntio

n fo

r 800

be

ndin

g cy

cles

at b

endi

ng a

ngle

of

60o

[17]

LMO

LiM

n 2O

4, LT

O L

i 4Ti 5O

12, L

FP L

iFeO

4, LC

O L

iCoO

2, C A

are

al c

apac

itanc

e, C

v vo

lum

etric

cap

acita

nce,

EA a

real

ene

rgy

dens

ity, E

v vo

lum

etric

ene

rgy

dens

ity, P

V vol

umet

ric p

ower

den

sity

, rG

O re

duce

d gr

aphe

ne o

xide

, NaD

C so

dium

deo

xych

olat

e

spectra of the electrochromic fiber. With − 1.5 V bias, the reflectance of the WO3 layer was quite high, and the removal of bias voltage significantly decreased the reflectance. Although this modified electrochromic fiber showed much improved multicolor performance, the golden color of the electrode reduces the applicability.

The superposition of red, green and blue can produce various colors. The π-conjugated organic polymers includ-ing Poly(3,4-ethylenedioxythiophene), poly(3-methylthio-phene), and poly(2,5-dimethoxyaniline) have been discussed and used as active materials to obtain red, green, and blue electrochromic devices [32, 117]. As shown in Fig. 11d, the electrochromic polymers were deposited on the surface of the core stainless-steel wires [32]. Then the gel electro-lyte was coated on the electrochromic layer, followed with another stainless-steel wire wrapping on. It can be seen that the PEDOT based electrochromic fiber are exhibited between red and blue (Fig. 11e, f) when different voltages were applied. These electrochromic fibers could respond quickly to voltage changes. Furthermore, these fibers were flexible and could be implanted into textiles.

Thermochromic Fibers

Thermochromic materials are compounds or mixtures that change their visible absorption spectra when heated or cooled. In particular, reversible thermochromic materials have the function of color memory [118]. It has the charac-teristics of discoloration at a specific temperature, showing a new color, and restoring to the original color when the temperature is restored to the initial temperature [119, 120]. Therefore, reversible thermochromic materials can be used to prepare fibers with chromic properties.

There are two main ways to prepare thermochromic fib-ers: composite fibers and surface coatings. The mechanical properties of composite thermochromic fibers are usually poor, which makes it difficult to meet the requirements of weaving. Lu et al. made an electrothermal chromatic fiber by coating the thermochromic polymers onto a conductive fiber. As shown in Fig. 12a, the elastic electrothermal chromatic fiber was fabricated by in situ polymerization of diacetylene monomer on the SWCNTs based elastic conductive fiber and following with coating a protected layer of silicone [33]. The electrothermal chromatic fibers exhibited highly flex-ible and stretchable properties. The chromatic transition of the fiber was reversible even under stretching up to 80% and bending angel of 180°. As exhibited in Fig. 12b–d, even if the electrothermal chromatic fiber was woven into a Chinese knot, wrapped around the glass rod and stretched during deformation, it was still well worked. However, this kind of thermochromic polymers-based fiber devices were only changing between blue and red.


1 3

In order to obtain abundant color change of thermochro-mic fibers, Li et al. prepared a series of thermochromic fib-ers which show orange, red, green, yellow, blue and white, turning by the electric heating. As shown in Fig. 12e, the as-prepared electrothermal chromatic fiber has a multiple layered sheath-core structure [121]. The inner and outer lay-ers of sheath-core fibers were the core layer of elastic pol-yurethane, the conductive layer of PE-RGO-TiO2, the pro-tective layer of PDMS, and the thermochromic ink in turn. Schematic diagram of electrothermal chromatic mechanism was given in Fig. 12f. When the circuit was switched on, the temperature increase and lead to the color change of the thermochromic ink layer. Besides, a series of thermochro-mic fibers that were prepared using varies inks with diverse colors and response temperatures are woven into a fabric (Fig. 12g). The three different colors fibers could change their colors twice respectively during the electric heating.

Structurally Colored Fibers

Structurally colored fibers refer to a kind of fibers with color on the surface or in the interior due to periodic struc-ture [113, 122]. Different from the traditional fiber color, the color of structurally colored fibers is mainly produced by the interaction of micro-nanostructure and light on its surface or inside [123, 124]. The color of the structurally

colored fibers can be changed by adjusting its inner or sur-face periodic structure. In addition, there is almost no energy consumption in the process of color changing of structurally colored fibers. Therefore, the preparation and application of structurally colored fibers have attracted extensive interest of researchers.

For the preparation of structurally colored fibers, the con-struction of periodic alignment of micro-and nano-materials within the fibers is a difficult and key problem. Shang et al. proposed a magnetically assisted self-assemble process to obtain the structurally colored fibers [125]. Induced by an external magnetic field, the superparamagnetic colloidal spheres were arranged into the one-dimensional chainlike structure and embedded in the stretchable PDMS matrix. Figure 13a schematically showed the color-changing pro-cess of the Fe3O4@C colloidal spheres embedding structur-ally colored fibers during the stretching and squeezing. As shown in Fig. 13b, the digital photos exhibit the real reflec-tive colors of the stretched and squeezed structurally colored fibers. The mechanical strain sensitivity of the structurally colored fiber can be explained in Fig. 13c. The tuning of the color of the fiber depends on the Bragg’s law, mλ = 2nd sinθ. The increase and decrease of lattice space in the chain-like structures caused the red- and blue-shift of the diffraction.

As we all know, there are abundant and colorful struc-tural colors in nature. Therefore, the study of structurally

Fig. 11 Electrochromic fiber devices. a Schematic of the preparation process of parallel coil electrodes [116]. b Digital pictures to display the color change of the fiber device. c Reflectance spectrum of the active material tungsten oxide (WO3) during coloring process. a–c Reproduced with permission [35]. Copyright 2018, Wiley. d Struc-

ture diagram of the electrochromic fibers and the electrochromic mechanism of the PEDOT based electrochromic layer. e The photo-graphs and f reflectance spectra of PEDOT based electrochromic fiber under reduced (left) and oxidized (right) states. d–f Reproduced with permission [32]. Copyright 2014, American Chemical Society


1 3

colored fibers is also imitating natural organisms. Kolle et al. presented a fiber rolling technique to fabricate the multilayer structurally colored fibers with an adjustable band-gap center frequency [126]. As schematically shown in Fig. 13d, the bilayer film consisting two elastomeric die-lectrics of PDMS and PSPI was firstly assembled. Follow-ing with rolling the above bilayer film on a thin glass fiber, the multilayer structurally colored fiber was obtained. The multilayer structurally colored fibers exhibited the tunable reflective colors during stretching it along its axis (Fig. 13e). The reason for the reflection band blueshifts of the fiber was that the Poisson’s ratio of two consisted elastic materials were comparable whereas the axial elongation renders the decrease of its diameter and thickness of each layer. Over 200 nm peak wavelength shift has been measured of the mul-tilayer structurally colored fiber during stretching its length over 200% (Fig. 13f).

Shape Deformable Fibers

Shape deformable materials can reversible change its posi-tion or shape in response to external stimuli, such as mag-netic field, electricity, irradiation, heat, and atmosphere [37, 38, 127, 128]. Since the 21st century, new advanced deformable materials have been widely studied and gradu-ally applied in biomimetic devices, biomimetic technology, and fashion decoration, such as shape memory polymer and alloy, phase change materials [129–132]. Fiber, as the unit of weaving fabric and further designing clothing, is the basis of clothing. Design and construction of controllable shape deformable fiber device is the key to realize the development of deformable clothing. Recently, researchers have devoted a lot to the study of shape deformable fibers, and have made great progress.

Electrically Controlled Deformable Fibers

In the era of electronic information, electric energy is the most convenient and easily controlled energy. People try to fabricate and construct electric-driven fiber materials when studying shape deformable fibers [37, 38, 131]. There are usually two ways to obtain electro-deformed fibers: one is dielectric elastomer-based electrically controlled deformable fibers, which drive the elastic deformation of the dielectric polymer by high voltage; the other is to drive the fiber defor-mation by Joule heat generated by electric energy. We will introduce the studies on deformable fibers based on above two principles.

For the shape deformable fibers, there are three main manifestations of their shape change: shrinkage, elongation and rotation. Liu et al. constructed a hierarchically buck-led sheath-core deformable fibers consisting of an elastic styrene(ethylene-butylene)-styrene (SEBS) rubber core and a parallel CNTs sheath [40]. As shown in Fig. 14a, the SEBS rubber core was firstly stretched above 1000% strain for preparing the elastic conductive fiber. For the prepara-tion of electrically controlled deformable fibers, the SEBS rubber layer acted as a dielectric was wrapped on a layer of paralleled CNT without stretch. The shape deformable fiber actuator was fabricated by twisting the sheath-core fiber. This electrically controlled deformable fiber could operate isobarically and exhibit both torsional and tensile actuation (Fig. 14b). The dependence of the retraction stroke and rota-tion behavior with the different twisted density were studied in Fig. 14c. The rotation angle and speed showed a linear behavior with twisted density. The tensile stroke was hardly changed with increasing twisted density.

Joule heating is one of the common ways to drive the deformation of a fiber. Kim et al. proposed a double helix twisted and coiled fiber actuator with both spandex and nylon which can be driven by Joule heating [133]. Fig-ure 14d exhibited the schematic of the double helix twisted and coiled fiber. The spandex sheath wraps around the nylon core and twisted to form a coiled shape. As displayed in Fig. 14e, 5 strands of the double helix twisted and coiled fiber can lifted a displacement of 75 mm of 1 kg load up during the Joule heating. Figure 14f and g schematically revealed the potential application of the double helix twisted and coiled fiber. Using the double helix twisted and coiled fiber bundles, the artificial limb for grasping/flexion motion was obtained.

Solvent Responsive Deformable Fibers

For the solvent-responsive deformable fiber, solvents are usually adsorbed and desorbed on the surface of the fiber to drive its deformation which is the direct way to change to shape or length of a fiber [39, 43, 45]. Chen et al. fab-ricated a hierarchically arranged helical fiber that could respond to solvent and vapor and display an elongation and rotation [39]. The hierarchically arranged helical fiber was constructed by helically assembling carbon nanotubes into fibers and then twisting the fibers together (Fig. 15a). As shown in Fig. 15b and c, the organic solvent or vapor suc-cessively infiltrate through the microscale and nanoscale gaps, which resulted in a rapid rotation and shrinkage of the hierarchically arranged helical fiber. The contractive stress of the fiber by absorbing ethanol was measured (Fig. 15d).


1 3

The contractive stress could reach up to about 1.0 MPa within 0.5 s, exhibiting a rapid response. An actuating tex-tile was also obtained by weaving 18 pieces of hierarchically arranged helical fibers and displayed driving behavior.

In addition to the CNTs-based shape deformable fib-ers, 2D structural graphene has also been used to fabricate solvent responsive deformable fiber. Fang et al. proposed a handedness-controlled fiber-shaped actuator responding to polar solvating species, such as acetone, methanol, and etha-nol [43]. As schematically shown in Fig. 15e, the continuous twisted graphene oxide fibers were processed by twisting and drawing the flexible graphene oxide belts. The actua-tion behavior of a suspended twisted graphene oxide fibers was observed by wetting the fiber with 0.05 mL acetone (Fig. 15f). The fiber was rotated with an angular speed of 633 rad s−1 in 0.7 s. The speeds of the forward and reverse rotation of twisted graphene oxide fibers were measured by using polar solvating species (Fig. 15g), indicating that the torsional rotation of the twisted fiber was repeatable. The

twisted graphene oxide fibers exhibited a controllable actua-tion by configuring two fibers in a homochiral unit.

Light‑Induced Deformable Fibers

Light inducing is a non-contact method to achieve mate-rial shape change, which has long-distance controllability [135–137]. Chen et al. introduced a contractile muscle-like actuation of a supramolecular material formed by the self-assembly of a photo-responsive amphiphilic molecular [41]. As shown in Fig. 16a, the UV light (λ = 365 nm) irradiation applied on the stable motor isomer induces photochemical isomerization on the central alkene bond. As schematically shown in Fig. 16b, the unidirectional alignment nanofiber bundles displayed a bending behavior during UV irradiation. The nanofiber bundle could be bending towards the pho-toirradiation of light source with a speed of about 1.8° s−1 (Fig. 16c). The in situ SAXS measurements was conducted to detect the structural changes of the nanofiber bundle

Fig. 12 Electrothermal chromatic fibers. a Preparation process of the stretchable electrothermal chromatic fiber. b An electrothermal chro-matic Chinese knot prepared from the electrothermal chromatic fiber. c An electrothermal chromatic fiber coiled on a glass rod. d In situ photographs during stretching. a–d Reproduced with permission [33]. Copyright 2016, The Royal Society of Chemistry. e Schematic illus-

tration of the structure of the stretchable electrothermal chromatic fiber. f Schematic diagram of color change mechanism during elec-tric heating. g Electrothermal chromatic fibers with patterns of letters are woven into fabrics. Reproduced with permission [121]. Copyright 2017, The Royal Society of Chemistry


1 3

during photoirradiation (Fig. 16d and e). After 60 s irradia-tion, the diffraction of (001) plane increased from 0° to 65°, corresponding to the bend angle of the nanofiber bundle.

Light-induced deformable fibers not only show simple rotation and bending, but also can be knitted into ordinary fabrics to drive fabric deformation. Shi et al. fabricated a pre-deformed twisted PASS/GO fiber which could display various actuation phenomena with the irradiation of a near-infrared light [134]. The metastable structured PASS/GO fiber was prepared by directly axial rotation of the hierar-chically wrinkled PASS/GO fiber. The component of the PASS/GO fiber was mainly including the hydrophilic PAAS and GO. As shown in Fig. 16f, the twisted PASS/GO fiber exhibited the contraction and rotation phenomena during the irradiation on the fiber, because of the photothermal effect of GO evaporated the adsorbed water molecule on the surface and slit of the fiber. Based on the light-responsive fiber, the

light-induced deformable fabric was obtained by directly weaving 3 pieces of twisted PAAS/GO fibers in a cotton fabric. The fabric could be folded upward to 90 degrees by the near infrared light irradiation (Fig. 16g). The remote controllable light-induced deformation fabric has potential use in shape changeable clothing.

Summary and Perspective

In this review, we first discuss the demands and the potential applications including portable devices, miniature devices, and wearable electronics of functional fiber devices, as well as the historical developments of manmade fibers. The recent progress in advanced functional fiber-shaped devices that consist of fiber-based energy harvesting devices, energy storage devices, fiber-shaped chromatic devices, and shape

Fig. 13 Structurally colored fibers. a Schematic illustration of the color change of the structurally colored fiber during squeezing and stretching. b The digital photos of the stretched, initial and squeezed fibers. c Schematic illustration of color change of the structurally colored fiber during mechanical strains. a–c Reproduced with permis-sion [125]. Copyright 2016, The Royal Society of Chemistry. d Sche-

matic illustration of the constructing of the multilayer structurally colored fibers. e Optical micrographs of the stretchable structurally colored fiber displaying the color changing upon mechanical strain. f The reflection spectrum of the structurally colored fiber correspond-ing to the optical micrographs in e. d–f Reproduced with permission [126]. Copyright 2013, Wiley


1 3

deformable fibers are systematically summarized. Particu-larly, the fabrication procedures and application character-istics of representative fiber-shaped multifunctional fiber devices are also discussed in details. These previous studies have opened up initial ideas for design, preparation and char-acterization of functional fiber devices and made tremendous progress, showing the advantages of fiber-shaped devices, including desired flexibility, miniaturization, weavability, and wearability. It promoted the research upsurge on mul-tifunctional fiber-shaped devices. These efforts also make people aware of the application prospects of functional fiber devices, and more look forward to the opportunity to use these functional fibers.

Despite the present research achievements on the fab-rication of multifunctional fiber-shaped devices, there are still many difficult problems to be solved to promote the

commercialization of functional fibers. For example, appli-cation stability, safety, and scale-up fabrication can be regarded as the critical challenge for the real application of functional fiber devices, especially for the integrated process of the functional fibers with the traditional textile industries and internal stress problems in complex application environ-ments. To further improve the practical applicability of the four representative functional fiber devices (energy harvest-ing, energy storage, color tuning, and shape deformation), the following research issues should be seriously studied. (1) For the energy harvesting fiber devices, the energy con-version efficiency needs to be further improved, and how to effectively store and use these collected energy needs to be further studied in detail. (2) Regarding the energy storage fibers, the stability and safety of electrodes and electrolytes of fiber-shaped batteries need to be guaranteed. Besides, as

Fig. 14 Electrically controlled deformable fibers. a The fabrication process of a hierarchically buckled sheath-core fibers with a SEBS rubber core and a parallel CNTs sheath. b The rotation angle and ten-sile stroke change of a twisted sheath-core fiber with different electric field. c The shape changes performance and tensile stroke character-istic of the twisted sheath-core fiber with different twisted density. a–c Reproduced with permission [40]. Copyright 2016, AAAS. d

The photographs of 5 strands of the double helix twisted and coiled fiber lifting 1 kg load by Joule heating. e Schematic and SEM images of the double helix twisted and coiled fiber. f Schematic showing the function of a double helix twisted and coiled fiber in an artificial limb. g Flexion motion of the artificial limb. d–g Reproduced with permission [133]. Copyright 2013, Wiley


1 3

a wearable energy storage device, the fiber-shaped batteries should be washable and stable under complex stress. For high power density energy storage fibers, the self-discharge of fiber-based supercapacitors need to be solved. (3) Con-cerning the chromotropic fibers, the multi-color characteris-tics of chromotropic fibers need to be studied and obtained. The stability of chromotropic fibers during light irradiation and exposing to high humidity should be seriously con-sidered. (4) For the deformable fibers, how to improve the

sensitivity of deformable fibers and obtain the large defor-mation, as well as the output force during deformation. Finally, large-scale fabrication can be considered as the most critical issues for multifunctional fiber devices. In order to realize their practical application, scale-up fabrication has to be carried out. In the longer-term view, the materials used in these multifunctional fiber devices are environmentally friendly and recyclable.

Fig. 15 Solvent responsive deformable fibers. a Schematic illustra-tion of the twisting process for creating the hierarchically arranged helical fiber actuator. b Schematic of the infiltration of the organic solvent into the fiber’s helical gaps. c Scheme of the contraction and rotation of the hierarchically arranged helical fiber. d Contractive stress curves for the hierarchically arranged helical fiber and single-ply helical fiber. a–d Reproduced with permission [39]. Copyright

2015, Springer Nature. e Scheme of a drawing–twisting procedure to fabricate continuous twisted graphene oxide fibers. f The rotation of solvent-driven twisted graphene oxide fibers. g The rotation speeds of twisted graphene oxide fibers driven by different polar solvating spe-cies. h Scheme of the responses of two united twisted graphene oxide fibers under the wetting of acetone. e–h Reproduced with permission [43]. Copyright 2019, The Royal Society of Chemistry


1 3

Acknowledgements This work was supported by the Science and Technology Commission of Shanghai Municipality [16JC1400700], the Program of Introducing Talents of Discipline to Universities [No.111-2-04], and the Innovative Research Team in University [IRT_16R13]. C. H. thanks the Natural Science Foundation of China [No. 51603037], DHU Distinguished Young Professor Program [LZB2019002], and Young Elite Scientists Sponsorship Program by CAST [2017QNRC001].

Compliance with ethical standards

Conflicts of interest The authors declare no competing financial in-terests.

References

1. Chen M, Ma YJ, Song J, Lai CF, Hu B. Smart clothing: con-necting human with clouds and big data for sustainable health monitoring. Mobile Netw Appl. 2016;21:825.

2. Hwang C, Chung T-L, Sanders EA. Attitudes and purchase inten-tions for smart clothing. Cloth Text Res J. 2016;34:207.

3. Loss C, Goncalves R, Lopes C, Pinho P, Salvado R. Smart coat with a fully-embedded textile antenna for IoT applications. Sen-sors (Basel). 2016;16:938.

4. Chen M, Ma Y, Li Y, Wu D, Zhang Y, Youn C-H. Wearable 2.0: enabling human-cloud integration in next generation healthcare systems. IEEE Commun Mag. 2017;55:54.

5. Honarvar MG, Latifi M. Overview of wearable electronics and smart textiles. J Text Inst. 2017;108:631.

6. Choi DY, Kim MH, Oh YS, Jung S-H, Jung JH, Sung HJ, Lee HW, Lee HM. Highly stretchable, hysteresis-free ionic liquid -based strain sensor for precise human motion monitoring. ACS Appl Mater Interfaces. 2017;9:1770.

Fig. 16 Light Induced deformable fibers. a The photochemical and thermal helix inversion steps of hierarchical supramolecular organiza-tion. b Scheme of bending behavior of the unidirectional alignment supramolecular bundles. c Photographs of the photo-deformation under irradiation of UV light. d, e 2D small-angle X-ray scattering (SAXS) images of fiber-shaped supramolecular bundle after irradia-tion for 0 s and 60 s. Reproduced with permission [41]. Copyright

2018, Springer Nature. f Schematic drawing of the rotation and reverse rotation of twisted PASS/GO fiber with simplified loading forces during the water evaporation and adsorption. g Scheme of the simplified loading forces of a piece of the twisted PASS/GO fiber in a cotton fabric. The bending behavior of the cotton fabric during near infrared irradiation. Reproduced with permission [134]. Copyright 2017, The Royal Society of Chemistry


1 3

7. Li L, Bai Y, Li L, Wang S, Zhang T. A superhydrophobic smart coating for flexible and wearable sensing electronics. Adv Mater. 2017;29:1702517.

8. Liu M, Pu X, Jiang C, Liu T, Huang X, Chen L, Du C, Sun J, Hu W, Wang ZL. Large-area all-textile pressure sensors for monitoring human motion and physiological signals. Adv Mater. 2017;29:1703700.

9. Yu A, Pu X, Wen R, Liu M, Zhou T, Zhang K, Zhang Y, Zhai J, Hu W, Wang ZL. Core-shell-yarn-based triboelectric nanogen-erator textiles as power cloths. ACS Nano. 2017;11:12764.

10. Chen B, Chen S, Dong B, Gao X, Xiao X, Zhou J, Hu J, Tang S, Yan K, Hu H, Sun K, Wen W, Zhao Z, Zou D. Electrical heating-assisted multiple coating method for fabrication of high-performance perovskite fiber solar cells by thickness control. Adv Mater Interfaces. 2017;4:1700833.

11. Fu X, Sun H, Xie S, Zhang J, Pan Z, Liao M, Xu L, Li Z, Wang B, Sun X, Peng H. A fiber-shaped solar cell showing a record power conversion efficiency of 10%. J Mater Chem A. 2018;6:45.

12. Varma SJ, Kumar KS, Seal S, Rajaraman S, Thomas J. Fiber-type solar cells, nanogenerators, batteries, and supercapacitors for wearable applications. Adv Sci. 2018;5:1800340.

13. Guo Y, Zhang X-S, Wang Y, Gong W, Zhang Q, Wang H, Brug-ger J. All-fiber hybrid piezoelectric-enhanced triboelectric nanogenerator for wearable gesture monitoring. Nano Energy. 2018;48:152.

14. Gong W, Hou C, Zhou J, Guo Y, Zhang W, Li Y, Zhang Q, Wang H. Continuous and scalable manufacture of amphibious energy yarns and textiles. Nat Commun. 2019;10:868.

15. Liu R, Liu Y, Chen J, Kang Q, Wang L, Zhou W, Huang Z, Lin X, Li Y, Li P, Feng X, Wu G, Ma Y, Huang W. Flexible wire-shaped lithium–sulfur batteries with fibrous cathodes assembled via capillary action. Nano Energy. 2017;33:325.

16. Wang Z, Ruan Z, Liu Z, Wang Y, Tang Z, Li H, Zhu M, Hung TF, Liu J, Shi Z, Zhi C. A flexible rechargeable zinc-ion wire-shaped battery with shape memory function. J Mater Chem A. 2018;6:8549.

17. Li J, Shao Y, Jiang P, Zhang Q, Hou C, Li Y, Wang H. 1T-molyb-denum disulfide/reduced graphene oxide hybrid fibers as high strength fibrous electrodes for wearable energy storage. J Mater Chem A. 2019;7:3143.

18. Zhang Y, Zhao Y, Ren J, Weng W, Peng H. Advances in wearable fiber-shaped lithium-ion batteries. Adv Mater. 2016;28:4524.

19. Yu J, Lu W, Smith JP, Booksh KS, Meng L, Huang Y, Li Q, Byun J-H, Oh Y, Yan Y, Chou T-W. A high performance stretchable asymmetric fiber-shaped supercapacitor with a core-sheath heli-cal structure. Adv Energy Mater. 2017;7:1600976.

20. Li L, Frey M. Preparation and characterization of cellulose nitrate-acetate mixed ester fibers. Polymer. 2010;51:3774.

21. Li X, Tabil LG, Panigrahi S. Chemical treatments of natural fiber for use in natural fiber-reinforced composites: a review. J Polym Environ. 2007;15:25.

22. John MJ, Anandjiwala RD. Recent developments in chemical modification and characterization of natural fiber-reinforced composites. Polym Compos. 2008;29:187.

23. Wang YL, Wan YZ, Dong XH, Cheng GX, Tao HM, Wen TY. Preparation and characterization of antibacterial viscose-based activated carbon fiber supporting silver. Carbon. 1998;36:1567.

24. Colom X, Carrillo F. Crystallinity changes in lyocell and viscose-type fibres by caustic treatment. Eur Polymer J. 2002;38:2225.

25. Huang ZH, Kang FY, Zheng YP, Yang JB, Liang KM. Adsorp-tion of trace polar methy-ethyl-ketone and non-polar benzene vapors on viscose rayon-based activated carbon fibers. Carbon. 2002;40:1363.

26. Hindeleh AM, Johnson DJ. Crystallinity and crystallite size measurement in polyamide and polyester fibers. Polymer. 1978;19:27.

27. Mit-uppatham C, Nithitanakul M, Supaphol P. Ultratine elec-trospun polyamide-6 fibers: effect of solution conditions on morphology and average fiber diameter. Macromol Chem Phys. 2004;205:2327.

28. Braun U, Schartel B, Fichera MA, Jaeger C. Flame retardancy mechanisms of aluminium phosphinate in combination with mel-amine polyphosphate and zinc borate in glass-fibre reinforced polyamide 6,6. Polym Degrad Stab. 2007;92:1528.

29. Azab MY, Hameed MFO, Obayya SSA. Multi-functional optical sensor based on plasmonic photonic liquid crystal fibers. Opt Quant Electron. 2017;49:49.

30. Chang H, Luo J, Gulgunje PV, Kumar S. Structural and func-tional fibers. In: Clarke DR (ed) Annual review of materi-als research, Vol 47. Annual Review of Materials Research. 2017;331.

31. Park S, Guo Y, Jia X, Choe HK, Grena B, Kang J, Park J, Lu C, Canales A, Chen R, Yim YS, Choi GB, Fink Y, Anikeeva P. One-step optogenetics with multifunctional flexible polymer fibers. Nat Neurosci. 2017;20:612.

32. Li KR, Zhang QH, Wang HZ, Li YG. Red, green, blue (RGB) electrochromic fibers for the new smart color change fabrics. ACS Appl Mater Interfaces. 2014;6:13043.

33. Lu X, Zhang Z, Sun X, Chen P, Zhang J, Guo H, Shao Z, Peng H. Flexible and stretchable chromatic fibers with high sensing reversibility. Chem Sci. 2016;7:5113.

34. Eh AL-S, Tan AWM, Cheng X, Magdassi S, Lee PS. Recent advances in flexible electrochromic devices: prerequisites, chal-lenges, and prospects. Energy Technol. 2018;6:33.

35. Zhou Y, Fang J, Wang H, Zhou H, Yan G, Zhao Y, Dai L, Lin T. Multicolor electrochromic fibers with helix-patterned electrodes. Adv Electronic Mater. 2018;4:1800104.

36. Cai L, Peng Y, Xu J, Zhou C, Zhou C, Wu P, Lin D, Fan S, Cui Y. Temperature regulation in colored infrared-transparent polyethylene textiles. Joule. 2019.https ://doi.org/10.1016/j.joule .2019.03.015

37. Foroughi J, Spinks GM, Wallace GG, Oh J, Kozlov ME, Fang SL, Mirfakhrai T, Madden JDW, Shin MK, Kim SJ, Baugh-man RH. Torsional carbon nanotube artificial muscles. Science. 2011;334:494.

38. Haines CS, Lima MD, Li N, Spinks GM, Foroughi J, Madden JD, Kim SH, Fang S, Jung de Andrade M, Goktepe F, Goktepe O, Mirvakili SM, Naficy S, Lepro X, Oh J, Kozlov ME, Kim SJ, Xu X, Swedlove BJ, Wallace GG, Baughman RH. Artificial muscles from fishing line and sewing thread. Science. 2014;343:868.

39. Chen P, Xu Y, He S, Sun X, Pan S, Deng J, Chen D, Peng H. Hierarchically arranged helical fibre actuators driven by solvents and vapours. Nat Nanotechnol. 2015;10:1077.

40. Liu ZF, Fang S, Moura FA, Ding JN, Jiang N, Di J, Zhang M, Lepro X, Galvao DS, Haines CS, Yuan NY, Yin SG, Lee DW, Wang R, Wang HY, Lv W, Dong C, Zhang RC, Chen MJ, Yin Q, Chong YT, Zhang R, Wang X, Lima MD, Ovalle-Robles R, Qian D, Lu H, Baughman RH. Stretchy electronics. Hierarchi-cally buckled sheath-core fibers for superelastic electronics, sen-sors, and muscles. Science. 2015;349:400.

41. Chen J, Leung FK, Stuart MCA, Kajitani T, Fukushima T, van der Giessen E, Feringa BL. Artificial muscle-like function from hierarchical supramolecular assembly of photoresponsive molec-ular motors. Nat Chem. 2018;10:132.

42. Mirvakili SM, Hunter IW. Artificial muscles: mechanisms, appli-cations, and challenges. Adv Mater. 2018;30:1704407.

43. Fang B, Xiao Y, Xu Z, Chang D, Wang B, Gao W, Gao C. Hand-edness-controlled and solvent-driven actuators with twisted fib-ers. Mater Horiz. 2019. https ://doi.org/10.1039/c8mh0 1647j

44. Jeong J-H, Mun TJ, Kim H, Moon JH, Lee DW, Baughman RH, Kim SJ. Carbon nanotubes–elastomer actuator driven electro-thermally by low-voltage. Nanoscale Adv. 2019;1:965.

https://doi.org/10.1016/j.joule.2019.03.015

https://doi.org/10.1016/j.joule.2019.03.015

https://doi.org/10.1039/c8mh01647j


1 3

45. Jia T, Wang Y, Dou Y, Li Y, Jung de Andrade M, Wang R, Fang S, Li J, Yu Z, Qiao R, Liu Z, Cheng Y, Su Y, Minary-Jolandan M, Baughman RH, Qian D, Liu Z. Moisture sensitive smart yarns and textiles from self-balanced silk fiber muscles. Adv Funct Mater. 2019:1808241.

46. Zeng W, Shu L, Li Q, Chen S, Wang F, Tao XM. Fiber-based wearable electronics: a review of materials, fabrication, devices, and applications. Adv Mater. 2014;26:5310.

47. Weng W, Chen P, He S, Sun X, Peng H. Smart electronic tex-tiles. Angew Chem Int Ed Engl. 2016;55:6140.

48. Pu X, Hu W, Wang ZL. Toward wearable self-charging power systems: the integration of energy-harvesting and storage devices. Small. 2018;14:1702817.

49. Li G, Zhu R, Yang Y. Polymer solar cells. Nat Photonics. 2012;6:153.

50. Peng M, Zou D. Flexible fiber/wire-shaped solar cells in pro-gress: properties, materials, and designs. J Mater Chem A. 2015;3:20435.

51. Li R, Xiang X, Tong X, Zou J, Li Q. Wearable double-twisted fibrous perovskite solar cell. Adv Mater. 2015;27:3831.

52. Chen T, Qiu L, Cai Z, Gong F, Yang Z, Wang Z, Peng H. Intertwined aligned carbon nanotube fiber based dye-sensitized solar cells. Nano Lett. 2012;12:2568.

53. Zhang Z, Yang Z, Wu Z, Guan G, Pan S, Zhang Y, Li H, Deng J, Sun B, Peng H. Weaving efficient polymer solar cell wires into flexible power textiles. Adv Energy Mater. 2014;4:1301750.

54. Pu X, Song W, Liu M, Sun C, Du C, Jiang C, Huang X, Zou D, Hu W, Wang ZL. Wearable power-textiles by integrating fabric triboelectric nanogenerators and fiber-shaped dye-sensitized solar cells. Adv Energy Mater. 2016;6:1601048.

55. Gong W, Hou C, Guo Y, Zhou J, Mu J, Li Y, Zhang Q, Wang H. A wearable, fibroid, self-powered active kinematic sensor based on stretchable sheath-core structural triboelectric fibers. Nano Energy. 2017;39:673.

56. Wu B, Guo Y, Hou C, Zhang Q, Li Y, Wang H. High-perfor-mance flexible thermoelectric devices based on all-inorganic hybrid films for harvesting low-grade heat. Adv Funct Mater. 2019.

57. Hou C, Wang H, Zhang Q, Li Y, Zhu M. Highly conductive, flexible, and compressible all-graphene passive electronic skin for sensing human touch. Adv Mater. 2014;26:5018.

58. Guo Y, Dun C, Xu J, Mu J, Li P, Gu L, Hou C, Hewitt CA, Zhang Q, Li Y, Carroll DL, Wang H. Ultrathin, washable, and large-area graphene papers for personal thermal management. Small. 2017;13:1702645.

59. Guo Y, Dun C, Xu J, Li P, Huang W, Mu J, Hou C, Hewitt CA, Zhang Q, Li Y, Carroll DL, Wang H. Wearable thermoelectric devices based on Au-decorated two-dimensional MoS2. ACS Appl Mater Interfaces. 2018;10:33316.

60. Zeng W, Tao X-M, Chen S, Shang S, Chan HLW, Choy SH. Highly durable all-fiber nanogenerator for mechanical energy harvesting. Energy Environ Sci. 2013;6:1631–2638.

61. Zhang T, Li K, Zhang J, Chen M, Wang Z, Ma S, Zhang N, Wei L. High-performance, flexible, and ultralong crystalline thermoelectric fibers. Nano Energy. 2017;41:35.

62. Ryan JD, Mengistie DA, Gabrielsson R, Lund A, Muller C. Machine-washable PEDOT:pSS dyed silk yarns for electronic textiles. ACS Appl Mater Interfaces. 2017;9:9045.

63. Lee JA, Aliev AE, Bykova JS, de Andrade MJ, Kim D, Sim HJ, Lepro X, Zakhidov AA, Lee JB, Spinks GM, Roth S, Kim SJ, Baughman RH. Woven-yarn thermoelectric textiles. Adv Mater. 2016;28:5038.

64. Dong B, Hu J, Xiao X, Tang S, Gao X, Peng Z, Zou D. High-efficiency fiber-shaped perovskite solar cell by vapor-assisted

deposition with a record efficiency of 10.79%. Adv Mater Tech-nol. 2019.

65. Gong W, Hou C, Zhou J, Guo Y, Zhang W, Li Y, Zhang Q, Wang H. Continuous and scalable manufacture of amphibious energy yarns and textiles. Nat Commun. 2019;10:868.

66. Dong K, Deng J, Ding W, Wang AC, Wang P, Cheng C, Wang Y-C, Jin L, Gu B, Sun B, Wang ZL. Versatile core-sheath yarn for sustainable biomechanical energy harvesting and real-time human-interactive sensing. Adv Energy Mater. 2018;8:1801114.

67. Yu X, Pan J, Zhang J, Sun H, He S, Qiu L, Lou H, Sun X, Peng H. A coaxial triboelectric nanogenerator fiber for energy harvesting and sensing under deformation. J Mater Chem A. 2017;5:6032.

68. Cheng Y, Lu X, Hoe Chan K, Wang R, Cao Z, Sun J, Wei Ho G. A stretchable fiber nanogenerator for versatile mechanical energy harvesting and self-powered full-range personal healthcare moni-toring. Nano Energy. 2017;41:511.

69. Dong K, Deng J, Zi Y, Wang YC, Xu C, Zou H, Ding W, Dai Y, Gu B, Sun B, Wang ZL. 3D orthogonal woven triboelectric nanogenerator for effective biomechanical energy harvest-ing and as self-powered active motion sensors. Adv Mater. 2017;29:1702648.

70. Wu C, Gu S, Zhang Q, Bai Y, Li M, Yuan Y, Wang H, Liu X, Yuan Y, Zhu N, Wu F, Li H, Gu L, Lu J. Electrochemically activated spinel manganese oxide for rechargeable aqueous alu-minum battery. Nat Commun. 2019;10:73.

71. Li H, Tang Z, Liu Z, Zhi C. Evaluating flexibility and wearability of flexible energy storage devices. Joule. 2019;3:613.

72. Shi QW, Zhong YR, Wu M, Wang HZ, Wang HL. High-capacity rechargeable batteries based on deeply cyclable lithium metal anodes. Proc Natl Acad Sci USA. 2018;115:5676.

73. Yang Y, Zhong Y, Shi Q, Wang Z, Sun K, Wang H. Electrocataly-sis in lithium sulfur batteries under lean electrolyte conditions. Angewandte Chemie Int Ed. 2018;130:15775–8.

74. Li L, Basu S, Wang Y, Chen Z, Hundekar P, Wang B, Shi J, Shi Y, Narayanan S, Koratkar N. Self-heating-induced healing of lithium dendrites. Science. 2018;359:1513.

75. Liu B, Zhang J-G, Xu W. Advancing lithium metal batteries. Joule. 2018;2:833–45.

76. Cheng XB, Zhang R, Zhao CZ, Zhang Q. Toward safe lithium metal anode in rechargeable batteries: a review. Chem Rev. 2017;117:10403.

77. Xu K. Electrolytes and interphases in Li-ion batteries and beyond. Chem Rev. 2014;114:11503.

78. Tarascon JM, Armand M. Issues and challenges facing recharge-able lithium batteries. Nature. 2001;414:359.

79. Li M, Zu M, Yu J, Cheng H, Li Q, Li B. Controllable synthesis of core-sheath structured aligned carbon nanotube/titanium dioxide hybrid fibers by atomic layer deposition. Carbon. 2017;123:151.

80. Lin H, Weng W, Ren J, Qiu L, Zhang Z, Chen P, Chen X, Deng J, Wang Y, Peng H. Twisted aligned carbon nanotube/silicon composite fiber anode for flexible wire-shaped lithium-ion bat-tery. Adv Mater. 2014;26:1217.

81. Fang X, Weng W, Ren J, Peng H. A cable-shaped lithium sulfur battery. Adv Mater. 2016;28:491.

82. Wang X, Pan Z, Yang J, Lyu Z, Zhong Y, Zhou G, Qiu Y, Zhang Y, Wang J, Li W. Stretchable fiber-shaped lithium metal anode. Energy Storage Mater. 2019.

83. Manthiram A, Yu X, Wang S. Lithium battery chemistries ena-bled by solid-state electrolytes. Nat Rev Mater. 2017;2:16103.

84. Sun J, Li Y, Zhang Q, Hou C, Shi Q, Wang H. A highly ionic conductive poly(methyl methacrylate) composite electrolyte with garnet-typed Li6.75La3Zr1.75Nb0.25O12 nanowires. Chem Eng J. 2019;375.

85. Rao J, Liu N, Zhang Z, Su J, Li L, Xiong L, Gao Y. All-fiber-based quasi-solid-state lithium-ion battery towards wearable


1 3

electronic devices with outstanding flexibility and self-healing ability. Nano Energy. 2018;51:425.

86. Wang Y, Chen C, Xie H, Gao T, Yao Y, Pastel G, Han X, Li Y, Zhao J, Fu KK, Hu L. 3D-printed all-fiber li-ion battery toward wearable energy storage. Adv Funct Mater. 2017;27:1703140.

87. Yadav A, De B, Singh SK, Sinha P, Kar KK. Facile devel-opment strategy of a single carbon-fiber-based all-solid-state flexible lithium-ion battery for wearable electronics. ACS Appl Mater Interfaces. 2019;11:7974.

88. Li L, Lou Z, Chen D, Jiang K, Han W, Shen G. Recent advances in flexible/stretchable supercapacitors for wearable electronics. Small. 2018;14:1702829.

89. Shao Y, El-Kady MF, Wang LJ, Zhang Q, Li Y, Wang H, Mousavi MF, Kaner RB. Graphene-based materials for flex-ible supercapacitors. Chem Soc Rev. 2015;44:3639.

90. Shao Y, El-Kady MF, Sun J, Li Y, Zhang Q, Zhu M, Wang H, Dunn B, Kaner RB. Design and mechanisms of asymmetric supercapacitors. Chem Rev. 2018;118:9233.

91. Li M, Zu M, Yu J, Cheng H, Li Q. Stretchable fiber super-capacitors with high volumetric performance based on buck-led MnO2/oxidized carbon nanotube fiber electrodes. Small. 2017;13:1602994.

92. El-Kady MF, Shao Y, Kaner RB. Graphene for batteries, super-capacitors and beyond. Nat Rev Mater. 2016;1:16033.

93. Huang G, Hou C, Shao Y, Zhu B, Jia B, Wang H, Zhang Q, Li Y. High-performance all-solid-state yarn supercapacitors based on porous graphene ribbons. Nano Energy. 2015;12:26.

94. Chen G, Chen T, Hou K, Ma W, Tebyetekerwa M, Cheng Y, Weng W, Zhu M. Robust, hydrophilic graphene/cellulose nanocrystal fiber-based electrode with high capacitive perfor-mance and conductivity. Carbon. 2018;127:218.

95. Liao M, Sun H, Zhang J, Wu J, Xie S, Fu X, Sun X, Wang B, Peng H. Multicolor, fluorescent supercapacitor fiber. Small. 2018;14:e1702052.

96. Li P, Jin Z, Peng L, Zhao F, Xiao D, Jin Y, Yu G. Stretchable all-gel-state fiber-shaped supercapacitors enabled by macromo-lecularly interconnected 3D graphene/nanostructured conduc-tive polymer hydrogels. Adv Mater. 2018;30:e1800124.

97. Gui Q, Wu L, Li Y, Liu J. Scalable wire-type asymmetric pseu-docapacitor achieving high volumetric energy/power densities and ultralong cycling stability of 100,000 times. Adv Sci. 2019.

98. Wang X, Jiang K, Shen G. Flexible fiber energy storage and integrated devices: recent progress and perspectives. Mater Today. 2015;18:265.

99. Yu D, Qian Q, Wei L, Jiang W, Goh K, Wei J, Zhang J, Chen Y. Emergence of fiber supercapacitors. Chem Soc Rev. 2015;44:647.

100. Fu KK, Cheng J, Li T, Hu L. Flexible batteries: from mechanics to devices. ACS Energy Lett. 2016;1:1065.

101. Huang Q, Wang D, Zheng Z. Textile-based electrochemical energy storage devices. Adv Energy Mater. 2016;6:1600783.

102. Meng F, Li Q, Zheng L. Flexible fiber-shaped supercapacitors: design, fabrication, and multi-functionalities. Energy Storage Mater. 2017;8:85.

103. Tebyetekerwa M, Marriam I, Xu Z, Yang S, Zhang H, Zabihi F, Jose R, Peng S, Zhu M, Ramakrishna S. Critical insight: chal-lenges and requirements of fibre electrodes for wearable electro-chemical energy storage. Energy Environ Sci. 2019.

104. Ren J, Li L, Chen C, Chen X, Cai Z, Qiu L, Wang Y, Zhu X, Peng H. Twisting carbon nanotube fibers for both wire-shaped micro-supercapacitor and micro-battery. Adv Mater. 2013;25:1155.

105. Sun C-F, Zhu H, Baker Iii EB, Okada M, Wan J, Ghemes A, Inoue Y, Hu L, Wang Y. Weavable high-capacity electrodes. Nano Energy. 2013;2:987.

106. Weng W, Sun Q, Zhang Y, Lin H, Ren J, Lu X, Wang M, Peng H. Winding aligned carbon nanotube composite yarns into

coaxial fiber full batteries with high performances. Nano Lett. 2014;14:3432.

107. Zhang Y, Bai W, Ren J, Weng W, Lin H, Zhang Z, Peng H. Super-stretchy lithium-ion battery based on carbon nanotube fiber. J Mater Chem A. 2014;2:11054–9.

108. Lee JA, Shin MK, Kim SH, Cho HU, Spinks GM, Wallace GG, Lima MD, Lepro X, Kozlov ME, Baughman RH, Kim SJ. Ultra-fast charge and discharge biscrolled yarn supercapacitors for textiles and microdevices. Nat Commun. 1970;2013:4.

109. Wang Q, Wang X, Xu J, Ouyang X, Hou X, Chen D, Wang R, Shen G. Flexible coaxial-type fiber supercapacitor based on NiCo2O4 nanosheets electrodes. Nano Energy. 2014;8:44.

110. Choi C, Kim KM, Kim KJ, Lepro X, Spinks GM, Baughman RH, Kim SJ. Improvement of system capacitance via weav-able superelastic biscrolled yarn supercapacitors. Nat Commun. 2016;7:13811.

111. Veerasubramani GK, Krishnamoorthy K, Pazhamalai P, Kim SJ. Enhanced electrochemical performances of graphene based solid-state flexible cable type supercapacitor using redox medi-ated polymer gel electrolyte. Carbon. 2016;105:638.

112. Wang Q, Wu Y, Li T, Zhang D, Miao M, Zhang A. High per-formance two-ply carbon nanocomposite yarn supercapacitors enhanced with a platinum filament and in situ polymerized poly-aniline nanowires. J Mater Chem A. 2016;4:3828.

113. Kolle M, Lethbridge A, Kreysing M, Baumberg JJ, Aizenberg J, Vukusic P. Bio-inspired band-gap tunable elastic optical multi-layer fibers. Adv Mater. 2013;25:2239.

114. Li R, Li K, Wang G, Li L, Zhang Q, Yan J, Chen Y, Zhang Q, Hou C, Li Y, Wang H. Ion-transport design for high-performance Na+-based electrochromics. ACS Nano. 2018;12:3759.

115. Liang H, Li R, Li C, Hou C, Li Y, Zhang Q, Wang H. Regulation of carbon content in MOF-derived hierarchical-porous NiO@C films for high-performance electrochromism. Mater Horiz. 2019;6:571.

116. Takamatsu S, Matsumoto K, Shimoyama I, editors. Stretchable yarn of display elements. 2009 IEEE 22nd International Confer-ence on Micro Electro Mechanical Systems; 2009: IEEE.

117. Sonmez G, Sonmez HB, Shen CKF, Wudl F. Red, green, and blue colors in polymeric electrochromics. Adv Mater. 2004:16:1905.

118. Ke Y, Yin Y, Zhang Q, Tan Y, Hu P, Wang S, Tang Y, Zhou Y, Wen X, Wu S, White TJ, Yin J, Peng J, Xiong Q, Zhao D, Long Y. Adaptive thermochromic windows from active plasmonic elas-tomers. Joule. 2019;3:858.

119. Zhang Y, Hu Z, Xiang H, Zhai G, Zhu M. Fabrication of visual textile temperature indicators based on reversible thermochromic fibers. Dyes Pigm. 2019;162:705.

120. Huang G, Liu L, Wang R, Zhang J, Sun X, Peng H. Smart color-changing textile with high contrast based on a single-sided con-ductive fabric. J Mater Chem C. 2016;4:7589.

121. Li Q, Li K, Fan H, Hou C, Li Y, Zhang Q, Wang H. Reduced graphene oxide functionalized stretchable and multicolor elec-trothermal chromatic fibers. J Mater Chem C. 2017;5:11448.

122. Isapour G, Lattuada M. Bioinspired stimuli-responsive color-changing systems. Adv Mater. 2018;30:1707069.

123. Liu ZF, Zhang QH, Wang HZ, Li YG. Structural colored fiber fabricated by a facile colloid self-assembly method in micro-space. Chem Commun. 2011;47:12801.

124. Gong X, Hou C, Zhang Q, Li Y, Wang H. Solvatochromic struc-tural color fabrics with favorable wearability properties. J Mater Chem C. 2019;7:4855.

125. Shang SL, Liu ZF, Zhang QH, Wang HZ, Li YG. Facile fabrica-tion of a magnetically induced structurally colored fiber and its strain-responsive properties. J Mater Chem C. 2015;3:11093.


1 3

126. Kolle M, Lethbridge A, Kreysing M, Baumberg JJ, Aizenberg J, Vukusic P. Bio-inspired band-gap tunable elastic optical multi-layer fibers. Adv Mater. 2013;25:2239.

127. Mu J, Hou C, Wang H, Li Y, Zhang Q, Zhu M. Origami-inspired active graphene-based paper for programmable instant self-fold-ing walking devices. Sci Adv. 2015;1:e1500533.

128. Shi Q, Hou C, Wang H, Zhang Q, Li Y. An electrically controlla-ble all-solid-state Au@graphene oxide actuator. Chem Commun. 2016;52:5816.

129. Ribeiro C, Costa CM, Correia DM, Nunes-Pereira J, Oliveira J, Martins P, Goncalves R, Cardoso VF, Lanceros-Mendez S. Elec-troactive poly(vinylidene fluoride)-based structures for advanced applications. Nat Protoc. 2018;13:681.

130. Chen J, Leung FK-C, Stuart MCA, Kajitani T, Fukushima T, van der Giessen E, Feringa BL. Artificial muscle-like function from hierarchical supramolecular assembly of photoresponsive molecular motors. Nat Chem. 2018;10:132.

131. Song Y, Zhou S, Jin K, Qiao J, Li D, Xu C, Hu D, Di J, Li M, Zhang Z, Li Q. Hierarchical carbon nanotube composite yarn muscles. Nanoscale. 2018;10:4077.

132. Chen Y, Millstein J, Liu Y, Chen GY, Chen X, Stucky A, Qu C, Fan J-B, Chang X, Soleimany A, Wang K, Zhong J, Liu J,

Gilliland FD, Li Z, Zhang X, Zhong JF. Single-cell digital lysates generated by phase-switch microfluidic device reveal transcrip-tome perturbation of cell cycle. ACS Nano. 2018;12:4687.

133. Kim K, Cho KH, Jung HS, Yang SY, Kim Y, Park JH, Jang H, Nam J-D, Koo JC, Moon H, Suk JW, Rodrigue H, Choi HR. Double helix twisted and coiled soft actuator from spandex and nylon. Adv Eng Mater. 2018;20:1800536.

134. Shi Q, Li J, Hou C, Shao Y, Zhang Q, Li Y, Wang H. A remote controllable fiber-type near-infrared light-responsive actuator. Chem Commun. 2017;53:11118.

135. Liu L, Onck PR. Topographical changes in photo-responsive liquid crystal films: a computational analysis. Soft Matter. 2018;14:2411.

136. Gu Y, Alt EA, Wang H, Li X, Willard AP, Johnson JA. Photos-witching topology in polymer networks with metal-organic cages as crosslinks. Nature. 2018;560:65.

137. Gupta P, Karothu DP, Ahmed E, Naumov P, Nath NK. Thermally twistable, photobendable, elastically deformable, and self-heala-ble soft crystals. Angewandte Chemie-Int Ed. 2018;57:8498.

Affiliations

Qiuwei Shi1,3 · Jianqi Sun1 · Chengyi Hou1 · Yaogang Li2 · Qinghong Zhang2 · Hongzhi Wang1

* Chengyi Hou [email protected]

* Hongzhi Wang [email protected]

1 State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, People’s Republic of China

2 Engineering Research Center of Advanced Glasses Manufacturing Technology, Ministry of Education, Donghua University, Shanghai 201620, People’s Republic of China

3 School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore

http://orcid.org/0000-0003-4142-2982

Advanced Functional Fiber and Smart Textile · Advanced Fiber Materials 1 3 comprehensive reviews provide researchers with a more systematic understanding of the advances in energy

Documents