(Presentation) Smart Textiles

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. GhoshNorth Carolina State University

Raleigh, NCItalian Technical Textile and Nonwovens Showcase, Raleigh, 2009

November 12, 2009 2

Context . . . . w Comfortable,w Durable,w Fashionable,w Protective,w Maintainable, etc.

w “Enhanced” Textiles with Additional Functionalitiesn Medical/Therapeutic,n Communication / Computation,n Threat detection,n Others.

w “Enhanced” Textiles with Additional Functionalitiesn Medical/Therapeutic,n Communication / Computation,n Threat detection,n Others.

Smart Textiles

http://www.foster-miller.com

http://www.foster-miller.com

November 12, 2009 3

Smart/Intelligent Textilesw Textile materials or systems that

are able to sense (and sometimes react in response to) an external stimuli (electrical, thermal, chemical, magnetic

or others).w Smart materials have one or more

characteristics that can be dramatically altered.

Smart Textiles

http://www.lord.com/Home/MagnetoRheologicalMRFluid

http://www.lord.com/Home/MagnetoRheologicalMRFluid

November 12, 2009 4

Design by Nature . . Really Smart!

w Single cell organisms (slime mold a giant amoeboid cell, species of algae) work autonomously,

w Sensors in the outer layer to detectw Signal processing and interpretationw Reaction (movement, etc.)

Cellular Informatics Lab., Hokkaido University, Japan, http://www.es.hokudai.ac.jp/labo/cell/research_e.html

Smart Textiles

e.g., Fiber-based sensors, (processor),actuators, . .

http://www.es.hokudai.ac.jp/labo/cell/research_e.html

November 12, 2009 5

Relevant Technologiesw Phase change materials w Shape memory materialsw Chromic materialsw Piezoelectric materialsw Electroactive materials, etc.

w Electronic textiles

Smart Textiles

November 12, 2009 6

Phase Change Materials (PCM)w Materials with high heat of fusion which, melting and

solidifying at certain temperatures, are capable of storing or releasing large amounts of energy.

w Some PCMs change phases within a range that is just above and just below human skin temperature. (Paraffin, Polyethylene glycol [PEG])

w coating fabrics with PCM microcapsules

w extruding PCMs with compatible polymers to produce PCM fibers

http://www.outlast.com

w Applications

n Heating, cooling

Smart Textiles

http://www.outlast.com

November 12, 2009 7

Shape Memory Materialsw Shape memory materials

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)

Smart Textiles

November 12, 2009 8

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

Smart Textiles

November 12, 2009 9

Electroactive Materialsw Electroactive materials modify their shape upon

application of electric field. wConducting polymerswCarbon nanotubeswDielectric elastomers

Smart Textiles

n Applications

n Artificial muscles

n Actuators

November 12, 2009 10

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

Smart Textiles

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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,

November 12, 2009 Smart Textiles

Products in the Market

November 12, 2009 Smart Textiles 12

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

http://www.vivometrics.com

http://www.vivometrics.com

Products in the Marketw Lumalive: Insertable LED

Technology by Phillipsw Enables clothing and

furnishings to have illuminated displays. w LEDS sewn into clothing and

powered by a portable battery pack.


Source :http://www.lumalive.com

http://www.lumalive.com

Products in the Marketw 'Thinking Carpet‘

equipped with sensors.w Sensors to measure

pressure, temperature and motion.n Climate control,

n Surveillance,

n Guidance,

http://www.vorwerk-carpet.com

November 12, 2009 14Smart Textiles

http://www.vorwerk-carpet.com

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Products in the Marketw Backpack with flexible display

n France Telecom, R & D

Car interior: Tsutani, Japan



w Fabric heating pads (Resistive heating)

w Silver loaded fibers are integrated in an undershirt power is supplied by a battery.


Source: http://www.warmx.de/

http://www.warmx.de/

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w Textile switches using quantum tunneling compositew Becomes electrically

conducting upon pressure

http://www.peratech.com/jacketsbags.php

http://www.fibretronic.com/

http://www.peratech.com/jacketsbags.php

http://www.fibretronic.com/

Dielectric Elastomer Based Prototype Fiber Actuators

Sohil Arora, Cuneyt Akbay

Long-term Goalw Fabrication of actuators substantially in the

form of textile fibers using electroactive polymers (EAP).

w Requirements are large displacement and moderate to low stress, n Focus on dielectric elastomers.

19November 12, 2009 Smart Textiles

Electroactive Polymersw Electroactive polymers (EAP) respond to

external electrical stimulation by displaying a significant shape change. n Ionic: Ionic Polymer Gels, Ionomeric Polymer-Metal Composites (IPMC), Conducting Polymers,

Carbon Nanotubes

n Electronic: Ferroelectric Polymers, Electrostrictive Polymers, Dielectric Polymers


n Actuatorsn Artificial Musclesn Power harvestingn Many others

n Dielectric elastomers (DE) constitute an imporrtantclass of EAPs

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Motivation: Natural Musclew Natural muscle present in animals

from elephants to butterfliesn Outstanding performance (energy

density)n Soft but strongn Resilient, fracture tolerant, noiselessn Scalable: regardless of the size, the

building block (sarcomere) is the same

w No existing actuator technology compare in overall performance

w If invented can find wide applications including many in textile products


Actuation Mechanism of DEsw Dielectric elastomers with low elastic modulus

show large actuation strain when subjected to an electrostatic field in a parallel plate capacitor with the dielectric material as the medium.

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• P is the Maxwell pressure

• ε is the relative dielectric constant

• ε0 is the permittivity of free space

• E is the applied electric field

• V is the applied voltage

• z is the film thickness


Actuator Fiber Prototype

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w Inner electrode : Low viscosity conductor

wDielectric polymer: Silicone/Polyurethane

wOuter electrode : Graphite loaded silicone


w To control anisotropy

w Axially Strained

w Uniformly Inflated

θ

r

z

/pr tθσ =

/ 2z pr tσ =

Uniaxially Prestrained

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0

2

4

6

8

0 20 40 60 80 100 120

50%100%150%200%250%

Axi

al S

trai

n (%

)

Applied Electric Field (KV/mm)

Silicone


w Axial Strain up to 7%: Relatively higher strains in silicone

w Radial strain up to 18%: Higher strains in silicone based prototypes

0

5

10

15

20

0 20 40 60 80 100 120

50%100%150%200%250%

Rad

ial S

trai

n (%

)

Applied Electric Field (KV/mm)

Silicone

25

Uniformly Prestrainedw Axial actuation strains up to 7.5%w Radial actuation strains up to 7%.


θ

r

z

/pr tθσ =

/ 2z pr tσ =

Actuation Strain

26November 12, 2009 Smart Textiles

w Uniformly prestrained (6.62 psi) silicone

Electrically Actuated Nanostructured Polymer (ENP)

Ravi Shankar, Arjun Krishnan, Pruthesh Vargantwar

ENP: Tri-block-copolymer w If the A endblocks are "hard" (glassy/crystalline) and

the B (a, b, and c) midblock is "soft" (rubbery), then the material behaves as a thermoplastic elastomer (TPE).

n The endblocks behave as physical crosslinks that can be heated into the liquid state.

w If an ABA copolymer is swollen in a B-selective solvent, then the A blocks can micellize to form cross-link sites and, hence, a physical gel.

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a – bridged midblocksb – coronal midblocksc – dangling ends

A A

A


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Mechanical Behavior: Tunable

w Elastic modulus can be controlled through MW and copolymer content.

w Strain energy density tunable

SEB217 SEB161


30

Mol. Wt. 217000 g/molSolvent Content- 95 wt. %Electrode –Silver GreasePrestrained (x,y)- (300,300)Break-down field- 18.8 MV/mAreal Actuation- 245%Linear Actuation-85%

Actuation Behavior of ENPsw Tunable electro-mechanical behavior


w Easy impedence matching

31

Fabric Porosity Control: Using Actuator Fibers

w Imagine if the fiber diameters can be changed on demand!


Composite Print Media for Electronic Textiles

Aylin Karahan, Saral Kalandhabhatla

Long-term Goalw Develop lightweight, conformable sensory

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.


Materialsw Polyvinyl chloride (PVC)w Dioctyl sebacate (DOS)

w Plasticizerw Carbon Nanofibers (CNF)w Epoxidised Soybean Oil (ESO)

w Thermal stabilizerw Binder (Binder 2001)


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.


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


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)


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%


Secant Modulus

Secant modulus (0-150%) as function of CNF content for various composites

w Significant increase is observed


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.


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.


Printed Fabricw Composite is screen-printed on fabric (Woven;

98% Nylon, 2% Spandex) for further evaluation.


Electrical Behavior of Printed Fabric

w Printed fabric shows ohmic(linear relationship I-V) character.w No evidence of Joule

heating


+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


8% CNF 50/50 PVC/DOS (long. direction)


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


47

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


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


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.


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)


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.


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).


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.


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(Presentation) Smart Textiles

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