Piezoresistive Sensors on Textiles by Inkjet Printing and Electroless Plating
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0920-S05-04
Piezoresistive Sensors on Textiles by Inkjet Printing and Electroless Plating Amit Sawhney, Animesh Agrawal, Prabir Patra, and Paul Calvert Department of Materials and Textiles, UMASS Dartmouth, North Dartmouth, Massachusetts, 02747 ABSTRACT We have printed arrays of strain sensors on textiles by inkjet printing of conducting lines and piezoresistive polymer (PEDOT) in order to provide detailed information about the response of a fabric in use. Conducting polymer has been printed onto polyamide and cellulose woven fabrics to form sensors using a modified HP inkjet print-head and X-Y linear positioning table. Good penetration and attachment is found on mercerized cotton but not on polyamide. Silver nitrate lines have been printed onto polyamide and converted to silver connectors by electroless plating. We observed that resistance of silver lines ranged from 0.7-1.5Ω/cm whereas for the conducting polymer it was 1-3 kΩ/mm by a four point probe method. The conducting polymer formed a surface coat on the fabric and also penetrated the weave. On stretching, the surface layer tended to crack but the embedded polymer acts as a strain gauge with a gauge factor of about 5. On the other hand the silver showed minimal change in resistance with stretching, as is required for connectors. Sensitivity towards temperature and humidity and the effect of orientation to stress and weave directions will be reported. Preliminary experiments show that these sensors attached to a sleeve could be effective for monitoring human joint motion.
INTRODUCTION Electronic textiles or e-textiles are a new emerging field of research that brings together specialists in information technology, microsystems, materials and textiles [1]. Studies in the area of "electronic textiles" have recently captured researchers' attention worldwide because the fabrication of electronic systems on a flexible substrate such as textiles represents a breakthrough in many areas of military and civilian application [2]. A large number of studies have focused on the inkjet printing of organic molecules, metal nanoparticles, carbon nano material dispersions to form unique structures with piezoresistive sensing and actuation behavior. However, there are only few reports on the preparation of flexible piezoresistive strain sensors with defined and comparable gage factors using drop on demand thermal inkjet printing. Inkjet printing is considered to be one of the key technologies in the field of defined polymer deposition particularly in relation to the manufacturing of soft matrix based sensors, polymeric light emitting diodes displays and other polymer electronics. The possibility of coating traditional textile fabrics with conducting polymers is quite recent. There are many types of conducting polymers such as polyacetylene, polypyrrole, polythiophene, polyphenylene, polyaniline, etc. Among these polypyrrole and polythiophene and their derivative show electrical conductivities that are stable at room temperature. Polythiophenes, in particular, serves as an obvi
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