electroactive textiles

8/2/2019 Electroactive Textiles

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Conventional smart fabrics are made by weaving metal wire into fabrics,

which combines with small electronic components, sensor & circuitry to

produce smart wearable garments.

Not mobile with the wearer.

Generate smart fabrics by directly coating conducting polymers onto a

substrate material, hence reducing the use of metal component within

fabrics.

They retain the natural texture of the material and the fabric can be

processed as normal.

These materials normally work as strain gauge and find applications in

wearable medical monitoring systems & in sports applications


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Existing C-P-based smart fabrics are typically thin pieces of

conducting polymer coated textiles that work as two-

dimensional strain gauges, i.e. they have to be stretched to give a

change in conductivity and are not sensitive to force normal to

the planar surface of the fabric.

This study reports the synthesis and properties of a new class

of C-P-based smart fabric prepared by chemically coating

polyurethane foam with conducting polymer (polypyrrole).

These materials are soft, compressible and versatile and, in

contrast to coated textiles, are sensitive to forces from all three

dimensions.


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Chemicals and materials

Pyrrole,

Naphthalene di-sulphonic acid (NDSA), and

Ferric chloride (FeCl3)

Pyrrole was distilled prior to use.

NDSA, and FeCl3 were used without further purification.

MilliQ water was used as the solvent for polymerisation and washing.

The polyurethane (PU) foam substrate (10 cm x 10 cm x 1.7 cm), was first

washed with soapy water and then rinsed with excess MilliQ water and

dried in air prior to use.


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300 ml solution

0.04M pyrrole & 5.4mM NDSA

Polyurethane (10 cm10 cm1.7 cm),

Soaked for 2 h

300 ml of 0.04M FeCl3 was added & stirred regularly for 2 hrat room temperature and then allowed to stand overnight

The black PPyPU foam, removed &triturated with MilliQ water

Drying in oven 40o covernight

Record Weight &Conductivity

Repeat for additional 3

times


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SAMPLE PREPERATION

The PPyPU foam was cut into specimens with dimensions of

1.7 cm1.7 cm1.3 cm.

Conductive self-adhering foil was used to connect the two

opposite end of the foam to the HP 34401A constant current

multimeter


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The resistance change (dR) vs. L0/L plots obtained from tworepeats of the foam compression study. The inset shows a plotof resistance change (dR) vs. % change in length using the samedata set as the solid triangle plot shown in the main feature


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Plot of normalised conductance (G/G0) vs. the stress applied onto aconducting foam sample. Data was normalised by using the ration ofthe conductance (G) of the material to the baseline conductance of

the material (G0).


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Plot of stress (force per unit area) vs. strain (L0 L/L0) applied onto aconducting foam sample obtained by an InstronTM instrument.Upward arrows indicate loading and downward arrows indicate

unloading process


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Normalised (R/R0) trace of PPy coated PU foam whenrepeatedly exposed to a force of 2.30 N.


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Real time trace of PPy coated PU foam as pressure sensor tomonitor ribcage movement while breathing


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The most important limitations are:

(1) drift in conductivity of the conducting foam over time and

(2) foam hysteresis after compression.

The first disadvantage (1) is completely dependent on the

chemical and physical stability of the conducting polymer coating.

The cause of drift can be due to environmental interferences such

as humidity effects and de-doping of PPy by amines that are

present in the atmosphere. Such effects may be prevented if the

foam is sealed in an airtight environment.

The mechanical properties of the PU substrate are largely

responsible for (2)

CONCLUSION

electroactive textiles

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