Emerging Technologies Emerging Technologies and Research in Smart and Research in Smart Textiles Textiles Aylin Hatice Karahan, Pruthesh Vargantwar Saral kalandhabhatla, Arjun Krishnan, Ravi Shankar Richard Spontak, John Muth, Tushar K. Ghosh North Carolina State University Raleigh, NC Italian Technical Textile and Nonwovens Showcase, Raleigh, 2009
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Emerging Technologies Emerging Technologies and Research in Smart and Research in Smart
remember their shape or geometry. w After deformation, can regain its
original shape by itself through heating (one-way effect).
Lendlein and Kelch, Angew. Chem. Int. Ed. 2002, 41, 2034-2057
w Applicationsn Insulation (PU film)n Porosity control (diaplex: Mitsubishi)
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Chromic Materialsw Chromic materials change their color reversibly
according to external environmental conditions.
w Applicationsn Fashionn Safetyn Camouflage
w photochromic: materials that change color in response to lightw thermochromic: materials that respond to heatw electrochromic: materials that respond to electricityw piezochromic materials that respond to pressurew solvatochromic: materials that respond to the presence of liquidw halochromic: materials that change color when pH changes occur
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Electroactive Materialsw Electroactive materials modify their shape upon
application of electric field. wConducting polymerswCarbon nanotubeswDielectric elastomers
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n Applications
n Artificial muscles
n Actuators
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Piezoelectric Materialsw Piezoelectric materials produce a voltage in response to
an applied force. Similarly, a deformation can be induced by the application of a voltage.
w Have two crystalline configurations. One is organized, while the other is not. Organization of the structure has to do with polarization of the molecules that make up the material.
w Applicationsn Energy harvestingn Actuator
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Electronic Textiles
w Level of integration may vary;n Materials level (fibers, dyes, etc.)
n Electronic capabilities designed or fabricated into a textile structure through integration of components. (resistive heaters, quantum tunneling switches, etc.)
n Textile products used as platforms to simply “carry” electronic devices.
w Textile products or systems with “integrated” electronic capabilities that are multifunctional, adaptive and responsivew sense (and sometimes respond to) environmental or other stimuli,
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Products in the Market
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w LifeShirt collects patient data using integrated sensors;n Pulmonary function with
respiratory bandsn Electrocardiography (ECG;
electrical activity of the heart)n Tracks posturen EEG (electroencephalogram)n Skin temp, Blood oxygen leveln Blood pressure
materials that are compatible with electronic textile (E-textile) products including body-worn sensors. n Use screen-printing to deposit an elastic and
conductive nanocomposite layer on fabric to fabricate piezoresistive strain sensors as well as transmission lines.
w Plasticizerw Carbon Nanofibers (CNF)w Epoxidised Soybean Oil (ESO)
w Thermal stabilizerw Binder (Binder 2001)
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Polyvinyl Chloride (PVC)
w PVC resins used are Solvin367, 372, and 376 form Solvay Corp.
w Nominal molecular weight of 41, 50, and 60 kg mol–1,
w Particle size of 0.1-3 µm.
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Carbon Nanofiber (CNF)w Vapor-grown CNF obtained from the Showa
Denko Corp. n Fiber diameter: 150 nmn Fiber length: 10 - 20 µm n Aspect ratio: 10 - 500 n Specific surface area: 13 m2/g
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Morphological Characterizationw Good dispersion. The fiber dia range from ca. 150-350 nm. w The PVC particles are seen mostly in clusters and the
individual particle sizes range from ca. 50-700 nm.w Texture of the fracture surface indicates good adhesion
between the particles and the matrix.
X-Sec. Image-1000x(8% CNF 50/50 PVC/DOS)
ó Surface Image-500x(8% CNF 50/50 PVC/DOS)
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ó Surface Image-20000x(8% CNF 50/50 PVC/DOS, printed)
Young’s Modulus
Young’s modulus as function of CNF content for various composites
w Young’s modulus increases significantly from 2.1 Mpa without CNF to 6.9 Mpa with 8% CNF for 50/50 plastisol
w The rise seems to be more rapid beyond percolation threshold of ca. 5wt%
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Secant Modulus
Secant modulus (0-150%) as function of CNF content for various composites
w Significant increase is observed
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Secant modulus (150-250%) as function of CNF content for various composites
w No significant increase is observedw Indicates matrix dominated
finite deformation
Piezoresistive Behaviorw Piezoresistivity describes the dependence of electrical
resistance of a material on applied deformation.w The resistance R of the conductor can be expressed as,
where ρ is the specific resistance or resistivity, L is the length, and A (= wx t) is the cross-section area of the conductor.
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The terms , and represent the geometrical and material components of piezoressitivity
Electrical Behaviorw Higher percolation
threshold for increasing DOS content.
w Percolation threshold ca. 5 wt% for 50/50 composite, slightly higher (6 wt%) for 35/65.
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Printed Fabricw Composite is screen-printed on fabric (Woven;
98% Nylon, 2% Spandex) for further evaluation.
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Electrical Behavior of Printed Fabric
w Printed fabric shows ohmic(linear relationship I-V) character.w No evidence of Joule
heating
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+V-
I
Piezoresistivity of Printed Fabricw Under uniaxial strain
resistance increases.w Gauge factor (G)
w ∆L/L = Strainw ΔR = Change in strain gauge resistancew R = Unstrained resistance of strain gauge
w Calculated Gauge factor is 5.6
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8% CNF 50/50 PVC/DOS (long. direction)
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Questions?Comments?
. . Thanks for your attention
46
Areal Actuation Strain of ENPsw The maximum areal
actuation strain goes down with higher co-polymer content
w Dielectric breakdown strength is higher for higher co-polymer content.
w Electro-mechanical coupling factors compare very well other dielectric EAPs.
SEB217 SEB161
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Uniaxially Prestrained: Blocking Forcew Decrease in blocking force with increased prestrainw Higher blocking force in polyurethane based prototypes
n Higher dielectric constant of polyurethane
0
10
20
30
40
50
60
0 20 40 60 80 100 120 140
50%100%
Blo
ckin
g Fo
rce
(cN
)
Applied Electric Field (KV/m)
Polyurethane
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Dioctyl Sebacate (DOS)w Dioctyl sebacate (DOS) manufactured by
Acros Organics with the molecular weight of 426.68 g mol-1 and density of 0.910 g/cm3
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Ritchie, P. D., Plasticizers, Stabilizers, and Fillers, Plastics Institue, London ILIFFE Books Ltd., 1972
Other Additives (ESO and Binder)w Epoxidised Soybean Oil (ESO) as a thermal
stabilizer and used as obtained from Spectrum Chemical Mfg Corp. n ESO does not affect viscosity of the plastisol.
w Binder 2001 (a member of Aromatic Polyisocyanatefamily), obtained from Nazdar SourceOne, is one of the common binders used for plastisol printing of polyester, polyamide or aramid fibres.
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Sample Preparation
DOS + ESO [Mix 60 sec.]
Add CNF & PVC [Mix 60 sec.]
Add Binder [Mix 60 sec.]
Composite for Printing
w Preparation of the plastisol composite was carriedout in three steps.
w Mixing was carried out in a high-shearplanetary mixer (Mazerustar KK-50S)
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Composite Film Composition
w Composites with four levels of PVC/DOS ratios (50/50, 45/55, 40/60, 35/65), and eight levels of CNF concentrations from 0 up to 10 wt% are prepared.
w The composite was compression molded into 0.7-1 mm thick films under static load at 160°C for 30 min.
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Morphological Characterizationw SEM studies of film
surfaces and cryofracturedsurfacesw Specimens, coated with 12-
13 nm of gold were examined in a field emission scanning electron microscope (FESEM: JEOL 6400F).
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Electrical Behavior: Measurementw Four-point probe using set-up
consisting of a current source (Keithley 6221) and a nano-voltmeter (Keithley 2182A).
w Electrometer (Keithley 6517B and Model 8009 Resistivity Test Fixture) for high-resistance.
w For piezoresistive behavior strip-like specimens, 50mm long and 25mm wide were used.
w The test sample was deformed at a strain rate of 0.02 min-1.