journal homepage: www.elsevier.com/locate/nanoen ergy Available online at www.sciencedire ct.com RAPID COMMUNICATION Two-dimensional rotary triboelectric nanogenerator as a portable and wearable power source for electronics Shuang Yang Kuang a , Jun Chen b , Xiao Bei Cheng a , Guang Zhu a,n , Zhong Lin Wang a,b a Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, China b School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA Received 14 May 2015; received in revised form 17 June 2015; accepted 9 July 2015 Available online 5 August 2015 KEYWORDS Energy harvesting; Triboelectric nano- generator; Self-powered; Wearable electronics Abstract Harvesting energy from ambient mechanical motions addresses limitations of traditional power suppl ies by prov iding a sustai ned electric power sourc e. Here, a high-p erfor mance rotar y tribo elect ric nanogene rator (r-TENG) is appl ied in a varie ty of circu mstances to speci cally harvest mechanical energy from human body motions. When rotating at 500 r min 1 , it can produce an ac electric output that has a current amplitude of 0.75 mA and a voltage amplitude of 200 V at a freque ncy of 750 Hz. Inte gra ted wit h str uctu ral component s tha t tra nsfe r mechanical motions and electric components that achieve power management, the r-TENG is demonstrated as a power source by harvesting energy from foot pedaling, arm swinging and foot pressure. The generated electricity can effectively charge consumer electronics such as a cellphone, which shows the promise of the r-TENG as a power source for portable, wearable and even implantable electronics. &2015 Elsevier Ltd. All rights reserved. Introduction The fast development of portable electronics requires a stand- alo ne , maintenance -fr ee an d susta ina bl e pow er source. Harvesting and converting ambient energy provides a feasible solution for this purpose. Mechanical motion is an attractive target for energy harvesting due to its great abundance and ubiquitousness[1–6] . Curr ent mech anic al ener gy harv esti ng tec hno log ies are ma inl y rel yin g on mec han isms inc lud ing electromagnetic effect, piezoelectric effect and electrostatic induction[1,7–9] . However, majo r challenges are still to be addressed, including low output power, structure complexity http://dx.doi.o rg/10.1016 /j.nanoen.2015.07.011 2211-2855/&2015 Elsevier Ltd. All rights reserved. n Corresponding author. E-mail address:[email protected](G. Zhu). Nano Energy (2015) 17, 10–16
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Shuang Yang Kuanga Jun Chenb Xiao Bei Chenga Guang Zhuan
Zhong Lin Wangab
aBeijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing 100083 ChinabSchool of Materials Science and Engineering Georgia Institute of Technology Atlanta GA 30332 USA
Received 14 May 2015 received in revised form 17 June 2015 accepted 9 July 2015
Available online 5 August 2015
KEYWORDSEnergy harvestingTriboelectric nano-
generatorSelf-poweredWearable electronics
Abstract
Harvesting energy from ambient mechanical motions addresses limitations of traditional power
supplies by providing a sustained electric power source Here a high-performance rotary
triboelectric nanogenerator (r-TENG) is applied in a variety of circumstances to speci1047297callyharvest mechanical energy from human body motions When rotating at 500 r min1 it can
produce an ac electric output that has a current amplitude of 075 mA and a voltage amplitude
of 200 V at a frequency of 750 Hz Integrated with structural components that transfer
mechanical motions and electric components that achieve power management the r-TENG is
demonstrated as a power source by harvesting energy from foot pedaling arm swinging and
foot pressure The generated electricity can effectively charge consumer electronics such as a
cellphone which shows the promise of the r-TENG as a power source for portable wearable
and even implantable electronics
amp 2015 Elsevier Ltd All rights reserved
Introduction
The fast development of portable electronics requires a stand-
alone maintenance-free and sustainable power source
Harvesting and converting ambient energy provides a feasible
solution for this purpose Mechanical motion is an attractive
target for energy harvesting due to its great abundance and
ubiquitousness [1ndash6] Current mechanical energy harvesting
technologies are mainly relying on mechanisms including
electromagnetic effect piezoelectric effect and electrostatic
induction [17ndash9] However major challenges are still to be
addressed including low output power structure complexity
httpdxdoiorg101016jnanoen201507011
2211-2855amp 2015 Elsevier Ltd All rights reserved
and dif 1047297culty in miniaturization [10ndash16] In recent years
triboelectric nanogenerators (TENG) that had a novel mechan-
ism were developed It is especially suitable as a portable
power source that harvests energy from body motions due to
its prominent advantages of high power density in terms of
power per volume as well as power per weight [11718]
Although various structures of TENGs have been developed
[1719ndash23] high-performance TENGs that are speci1047297cally
designed for harvesting energy from body motions and can
provide useful amount of output power were rarely reported
Here we report a series of solutions for practically poweringand charging portable electronics by harvesting energy from
body motions including foot pedaling hand swinging and foot
pressure These approaches are all based on high-performance
two-dimensional rotary TENGs (r-TENG) Enabled by a design of
two radial-arrayed 1047297ne electrodes that are complementary on
the same plane the planar-structured r-TENG produces peri-
odically changing triboelectric potential that induces alternat-
ing currents between electrodes At a rotating rate of
500 r min1 it can deliver a continuous ac output that has a
short-circuit current of 075 mA in amplitude and an open-
circuit voltage of 200 V at a frequency of 750 Hz By integrating
the r-TENG with other mechanical components it can effec-
tively utilize motions from different parts of human body When
installed onto a bicycle the r-TENG can convert mechanical
energy of foot pedaling into electricity powering an array of
small electronics as well as charging a cellphone Besides it can
harness energy from arm swinging as well as foot pressing
during normal walking Through a power management circuit
the electric output can be used to charge capacitors and
batteries unambiguously demonstrating the r-TENG as a pro-
mising power source for portable wearable and even poten-
tially implantable electronics
Results and discussions
A r-TENG is composed of mainly two parts a stator and a
rotator as depicted in Figure 1a The rotator is a collection
of 90 radially-arrayed sectors made of copper For the
stator it is composed of mainly three parts a layer of
polymethyl methacrylate (PMMA) as a substrate a layer of
electrodes and a layer of polytetra1047298uoroethylene (PTFE) as
an electri1047297cation layer The electrode layer is composed of
electrode A and electrode B which have complementary
patterns separated by 1047297ne gaps in between as shown in the
zoom-in sketches of the inner and outer sections of the
stator in Figure 1a As photographed in Figure 1b and c both
Figure 1 Structural design and working principle of the r-TENG (a) Schematic sketches of the r-TENG (b c) Photographs of a rotatorand a stator (scale bar 3 cm) (d) Charge distribution on open-circuit condition (e) Charge distribution on short-circuit condition
electrodes The electricity generation process from a single
sector unit is depicted in Figure 1d and e Here two-
dimensional schematic illustrations of the charge distribu-
tion are used for interpretation To begin with when the
rotator rotates coaxially against the stator charge transfer
takes place at the contact interface Negative triboelectric
charges are produced on the PTFE surface since it has a
much stronger tendency to be negatively charged
(Figure 1d) On the open-circuit condition electrons cannot
transfer between electrodes The open-circuit voltage is
then essentially the electric potential difference between
the two electrodes At the initial state when the copper-
made stator is aligned with the left electrode (Figure 1d)
the electric potential of the left and right electrodes is
maximized and minimized respectively which corresponds
to a maximum electric potential difference between the
electrodes When the rotator starts to spin such a potential
difference will diminish to zero when the rotator reaches
the middle point Further rotation will result in a reversely
built-up electric potential difference between the electro-
des as illustrated in the Figure 1d If the two electrodes are
electrically connected namely on the short-circuit condi-tion the induced free electrons can 1047298ow between the
electrodes due to electrostatic induction As the rotator
starts to spin free electrons will keep 1047298owing from the left
electrode to the right electrode until the rotator is in
alignment with the right electrode (Figure 1e) Further
rotation will then generate a current in the opposite
direction
To characterize the electric output of the r-TENG a
programmable motor was employed to provide a mechanical
rotation source at a controlled rate At a rotating rate of
500 r min1 the short-circuit current (Isc) of the r-TENG has
a continuous ac manner at an amplitude of 075 mA and a
frequency of 750 Hz The open-circuit voltage (V oc) exhibits
a peak-to-peak value of 400 V at the same frequency In
order to realize impedance match between the TENG that
has high output impedance and conventional electronics
that are known for low input impedance we transformed
the electric output to enhance the output current at the
expense of the output voltage As shown in Figure 2c and d
the current amplitude is greatly boosted to about 16 mA
while the output voltage drops to about 32 V By doing so
the impedance match ensures that the maximum amount of
electric output can be extracted from the TENG for
practical use
To demonstrate practical applications we designed and
fabricated three types of devices that are based on the r-
TENG First we installed a r-TENG that is 150 mm in
diameter on the wheel axis of a 1047297tness bicycle When being
pedaled the relative rotation between the rotator and the
stator generates high-level electric output As shown in the
Figure 3a and b at a rotation rate of about 183 r min1 the
current amplitude after being tuned by transformers
reaches as high as 13 mA and the voltage amplitude
exceeds 36 V When directly using the generated electricitywe could simultaneously power over 20 LED lamps (12 V
06 W for each) which is demonstrated in Figure 3c and
Supplementary Movie S1 Besides powering small electro-
nics the electric output could be used to charge electro-
nics Here besides transformers we added recti1047297ers
capacitors and voltage regulators to construct a power
management circuit that can provide an output voltage at
a preset value (diagramed in Supplementary Figure S1)
When being plugged into a cellphone a charging system
consisting of the r-TENG and the power management circuit
can effectively charge a battery When being triggered by
pedaling the charging current shoots to 13 mA (Figure 3d)
Figure 4 Demonstration of the r-TENG for harvesting energy from human arm swinging (a) Schematic of the entire device (b) Diagram
of the device when the arm is stretched (c) Diagram of the device when the arm is bent (d) Short-circuit current and (e) open-circuitvoltage of the r-TENG at a swing frequency of 5 Hz (f) Transformed and recti1047297ed current On the right is an enlarged view of the current
signal (g) Photograph showing about 60 LEDs being lighted up simutaneously when the r-TENG is being swung (scale bar 10 cm)
(h) Charging curve of a capacitor with a capacitance of 4700 μF Inset is the diagram of a power management circuit
and dif 1047297culty in miniaturization [10ndash16] In recent years
triboelectric nanogenerators (TENG) that had a novel mechan-
ism were developed It is especially suitable as a portable
power source that harvests energy from body motions due to
its prominent advantages of high power density in terms of
power per volume as well as power per weight [11718]
Although various structures of TENGs have been developed
[1719ndash23] high-performance TENGs that are speci1047297cally
designed for harvesting energy from body motions and can
provide useful amount of output power were rarely reported
Here we report a series of solutions for practically poweringand charging portable electronics by harvesting energy from
body motions including foot pedaling hand swinging and foot
pressure These approaches are all based on high-performance
two-dimensional rotary TENGs (r-TENG) Enabled by a design of
two radial-arrayed 1047297ne electrodes that are complementary on
the same plane the planar-structured r-TENG produces peri-
odically changing triboelectric potential that induces alternat-
ing currents between electrodes At a rotating rate of
500 r min1 it can deliver a continuous ac output that has a
short-circuit current of 075 mA in amplitude and an open-
circuit voltage of 200 V at a frequency of 750 Hz By integrating
the r-TENG with other mechanical components it can effec-
tively utilize motions from different parts of human body When
installed onto a bicycle the r-TENG can convert mechanical
energy of foot pedaling into electricity powering an array of
small electronics as well as charging a cellphone Besides it can
harness energy from arm swinging as well as foot pressing
during normal walking Through a power management circuit
the electric output can be used to charge capacitors and
batteries unambiguously demonstrating the r-TENG as a pro-
mising power source for portable wearable and even poten-
tially implantable electronics
Results and discussions
A r-TENG is composed of mainly two parts a stator and a
rotator as depicted in Figure 1a The rotator is a collection
of 90 radially-arrayed sectors made of copper For the
stator it is composed of mainly three parts a layer of
polymethyl methacrylate (PMMA) as a substrate a layer of
electrodes and a layer of polytetra1047298uoroethylene (PTFE) as
an electri1047297cation layer The electrode layer is composed of
electrode A and electrode B which have complementary
patterns separated by 1047297ne gaps in between as shown in the
zoom-in sketches of the inner and outer sections of the
stator in Figure 1a As photographed in Figure 1b and c both
Figure 1 Structural design and working principle of the r-TENG (a) Schematic sketches of the r-TENG (b c) Photographs of a rotatorand a stator (scale bar 3 cm) (d) Charge distribution on open-circuit condition (e) Charge distribution on short-circuit condition
electrodes The electricity generation process from a single
sector unit is depicted in Figure 1d and e Here two-
dimensional schematic illustrations of the charge distribu-
tion are used for interpretation To begin with when the
rotator rotates coaxially against the stator charge transfer
takes place at the contact interface Negative triboelectric
charges are produced on the PTFE surface since it has a
much stronger tendency to be negatively charged
(Figure 1d) On the open-circuit condition electrons cannot
transfer between electrodes The open-circuit voltage is
then essentially the electric potential difference between
the two electrodes At the initial state when the copper-
made stator is aligned with the left electrode (Figure 1d)
the electric potential of the left and right electrodes is
maximized and minimized respectively which corresponds
to a maximum electric potential difference between the
electrodes When the rotator starts to spin such a potential
difference will diminish to zero when the rotator reaches
the middle point Further rotation will result in a reversely
built-up electric potential difference between the electro-
des as illustrated in the Figure 1d If the two electrodes are
electrically connected namely on the short-circuit condi-tion the induced free electrons can 1047298ow between the
electrodes due to electrostatic induction As the rotator
starts to spin free electrons will keep 1047298owing from the left
electrode to the right electrode until the rotator is in
alignment with the right electrode (Figure 1e) Further
rotation will then generate a current in the opposite
direction
To characterize the electric output of the r-TENG a
programmable motor was employed to provide a mechanical
rotation source at a controlled rate At a rotating rate of
500 r min1 the short-circuit current (Isc) of the r-TENG has
a continuous ac manner at an amplitude of 075 mA and a
frequency of 750 Hz The open-circuit voltage (V oc) exhibits
a peak-to-peak value of 400 V at the same frequency In
order to realize impedance match between the TENG that
has high output impedance and conventional electronics
that are known for low input impedance we transformed
the electric output to enhance the output current at the
expense of the output voltage As shown in Figure 2c and d
the current amplitude is greatly boosted to about 16 mA
while the output voltage drops to about 32 V By doing so
the impedance match ensures that the maximum amount of
electric output can be extracted from the TENG for
practical use
To demonstrate practical applications we designed and
fabricated three types of devices that are based on the r-
TENG First we installed a r-TENG that is 150 mm in
diameter on the wheel axis of a 1047297tness bicycle When being
pedaled the relative rotation between the rotator and the
stator generates high-level electric output As shown in the
Figure 3a and b at a rotation rate of about 183 r min1 the
current amplitude after being tuned by transformers
reaches as high as 13 mA and the voltage amplitude
exceeds 36 V When directly using the generated electricitywe could simultaneously power over 20 LED lamps (12 V
06 W for each) which is demonstrated in Figure 3c and
Supplementary Movie S1 Besides powering small electro-
nics the electric output could be used to charge electro-
nics Here besides transformers we added recti1047297ers
capacitors and voltage regulators to construct a power
management circuit that can provide an output voltage at
a preset value (diagramed in Supplementary Figure S1)
When being plugged into a cellphone a charging system
consisting of the r-TENG and the power management circuit
can effectively charge a battery When being triggered by
pedaling the charging current shoots to 13 mA (Figure 3d)
Figure 4 Demonstration of the r-TENG for harvesting energy from human arm swinging (a) Schematic of the entire device (b) Diagram
of the device when the arm is stretched (c) Diagram of the device when the arm is bent (d) Short-circuit current and (e) open-circuitvoltage of the r-TENG at a swing frequency of 5 Hz (f) Transformed and recti1047297ed current On the right is an enlarged view of the current
signal (g) Photograph showing about 60 LEDs being lighted up simutaneously when the r-TENG is being swung (scale bar 10 cm)
(h) Charging curve of a capacitor with a capacitance of 4700 μF Inset is the diagram of a power management circuit
electrodes The electricity generation process from a single
sector unit is depicted in Figure 1d and e Here two-
dimensional schematic illustrations of the charge distribu-
tion are used for interpretation To begin with when the
rotator rotates coaxially against the stator charge transfer
takes place at the contact interface Negative triboelectric
charges are produced on the PTFE surface since it has a
much stronger tendency to be negatively charged
(Figure 1d) On the open-circuit condition electrons cannot
transfer between electrodes The open-circuit voltage is
then essentially the electric potential difference between
the two electrodes At the initial state when the copper-
made stator is aligned with the left electrode (Figure 1d)
the electric potential of the left and right electrodes is
maximized and minimized respectively which corresponds
to a maximum electric potential difference between the
electrodes When the rotator starts to spin such a potential
difference will diminish to zero when the rotator reaches
the middle point Further rotation will result in a reversely
built-up electric potential difference between the electro-
des as illustrated in the Figure 1d If the two electrodes are
electrically connected namely on the short-circuit condi-tion the induced free electrons can 1047298ow between the
electrodes due to electrostatic induction As the rotator
starts to spin free electrons will keep 1047298owing from the left
electrode to the right electrode until the rotator is in
alignment with the right electrode (Figure 1e) Further
rotation will then generate a current in the opposite
direction
To characterize the electric output of the r-TENG a
programmable motor was employed to provide a mechanical
rotation source at a controlled rate At a rotating rate of
500 r min1 the short-circuit current (Isc) of the r-TENG has
a continuous ac manner at an amplitude of 075 mA and a
frequency of 750 Hz The open-circuit voltage (V oc) exhibits
a peak-to-peak value of 400 V at the same frequency In
order to realize impedance match between the TENG that
has high output impedance and conventional electronics
that are known for low input impedance we transformed
the electric output to enhance the output current at the
expense of the output voltage As shown in Figure 2c and d
the current amplitude is greatly boosted to about 16 mA
while the output voltage drops to about 32 V By doing so
the impedance match ensures that the maximum amount of
electric output can be extracted from the TENG for
practical use
To demonstrate practical applications we designed and
fabricated three types of devices that are based on the r-
TENG First we installed a r-TENG that is 150 mm in
diameter on the wheel axis of a 1047297tness bicycle When being
pedaled the relative rotation between the rotator and the
stator generates high-level electric output As shown in the
Figure 3a and b at a rotation rate of about 183 r min1 the
current amplitude after being tuned by transformers
reaches as high as 13 mA and the voltage amplitude
exceeds 36 V When directly using the generated electricitywe could simultaneously power over 20 LED lamps (12 V
06 W for each) which is demonstrated in Figure 3c and
Supplementary Movie S1 Besides powering small electro-
nics the electric output could be used to charge electro-
nics Here besides transformers we added recti1047297ers
capacitors and voltage regulators to construct a power
management circuit that can provide an output voltage at
a preset value (diagramed in Supplementary Figure S1)
When being plugged into a cellphone a charging system
consisting of the r-TENG and the power management circuit
can effectively charge a battery When being triggered by
pedaling the charging current shoots to 13 mA (Figure 3d)
Figure 4 Demonstration of the r-TENG for harvesting energy from human arm swinging (a) Schematic of the entire device (b) Diagram
of the device when the arm is stretched (c) Diagram of the device when the arm is bent (d) Short-circuit current and (e) open-circuitvoltage of the r-TENG at a swing frequency of 5 Hz (f) Transformed and recti1047297ed current On the right is an enlarged view of the current
signal (g) Photograph showing about 60 LEDs being lighted up simutaneously when the r-TENG is being swung (scale bar 10 cm)
(h) Charging curve of a capacitor with a capacitance of 4700 μF Inset is the diagram of a power management circuit
electrodes The electricity generation process from a single
sector unit is depicted in Figure 1d and e Here two-
dimensional schematic illustrations of the charge distribu-
tion are used for interpretation To begin with when the
rotator rotates coaxially against the stator charge transfer
takes place at the contact interface Negative triboelectric
charges are produced on the PTFE surface since it has a
much stronger tendency to be negatively charged
(Figure 1d) On the open-circuit condition electrons cannot
transfer between electrodes The open-circuit voltage is
then essentially the electric potential difference between
the two electrodes At the initial state when the copper-
made stator is aligned with the left electrode (Figure 1d)
the electric potential of the left and right electrodes is
maximized and minimized respectively which corresponds
to a maximum electric potential difference between the
electrodes When the rotator starts to spin such a potential
difference will diminish to zero when the rotator reaches
the middle point Further rotation will result in a reversely
built-up electric potential difference between the electro-
des as illustrated in the Figure 1d If the two electrodes are
electrically connected namely on the short-circuit condi-tion the induced free electrons can 1047298ow between the
electrodes due to electrostatic induction As the rotator
starts to spin free electrons will keep 1047298owing from the left
electrode to the right electrode until the rotator is in
alignment with the right electrode (Figure 1e) Further
rotation will then generate a current in the opposite
direction
To characterize the electric output of the r-TENG a
programmable motor was employed to provide a mechanical
rotation source at a controlled rate At a rotating rate of
500 r min1 the short-circuit current (Isc) of the r-TENG has
a continuous ac manner at an amplitude of 075 mA and a
frequency of 750 Hz The open-circuit voltage (V oc) exhibits
a peak-to-peak value of 400 V at the same frequency In
order to realize impedance match between the TENG that
has high output impedance and conventional electronics
that are known for low input impedance we transformed
the electric output to enhance the output current at the
expense of the output voltage As shown in Figure 2c and d
the current amplitude is greatly boosted to about 16 mA
while the output voltage drops to about 32 V By doing so
the impedance match ensures that the maximum amount of
electric output can be extracted from the TENG for
practical use
To demonstrate practical applications we designed and
fabricated three types of devices that are based on the r-
TENG First we installed a r-TENG that is 150 mm in
diameter on the wheel axis of a 1047297tness bicycle When being
pedaled the relative rotation between the rotator and the
stator generates high-level electric output As shown in the
Figure 3a and b at a rotation rate of about 183 r min1 the
current amplitude after being tuned by transformers
reaches as high as 13 mA and the voltage amplitude
exceeds 36 V When directly using the generated electricitywe could simultaneously power over 20 LED lamps (12 V
06 W for each) which is demonstrated in Figure 3c and
Supplementary Movie S1 Besides powering small electro-
nics the electric output could be used to charge electro-
nics Here besides transformers we added recti1047297ers
capacitors and voltage regulators to construct a power
management circuit that can provide an output voltage at
a preset value (diagramed in Supplementary Figure S1)
When being plugged into a cellphone a charging system
consisting of the r-TENG and the power management circuit
can effectively charge a battery When being triggered by
pedaling the charging current shoots to 13 mA (Figure 3d)
Figure 4 Demonstration of the r-TENG for harvesting energy from human arm swinging (a) Schematic of the entire device (b) Diagram
of the device when the arm is stretched (c) Diagram of the device when the arm is bent (d) Short-circuit current and (e) open-circuitvoltage of the r-TENG at a swing frequency of 5 Hz (f) Transformed and recti1047297ed current On the right is an enlarged view of the current
signal (g) Photograph showing about 60 LEDs being lighted up simutaneously when the r-TENG is being swung (scale bar 10 cm)
(h) Charging curve of a capacitor with a capacitance of 4700 μF Inset is the diagram of a power management circuit