PPy-coated Electrically Conducting Fabrics with High Strain Sensitivity
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0920-S05-02
PPy-coated Electrically Conducting Fabrics with High Strain Sensitivity P. Xue, X.M. Tao, H.Y. Tsang, and M.Y Leung Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China, People's Republic of Abstract This paper studies a flexible strain sensor from PPy-coated fabric prepared by a chemical vapor deposition procedure under low temperature. The mechanisms of its strain sensing behavior were investigated. In-situ tensile tests in a scanning electron microscope (SEM) were conducted for PPy-coated electrically conducting yarns prepared in the same procedure as that for the PPy-coated fabric. The results exhibited the developed PPy-coated fabric possessed the high strain sensitivity and the large workable strain range, which attribute to the high performance of PPy-coated PU fibers and the crack-opening and crack-closing mechanism happened on the surface of PU fibers, as well as the excellent properties of knitted fabric structure. Introduction Electrically conductive textiles have many potential applications such as strain sensors [1-3], sport garments, motion capture device [4, 5], electrotherapy treatment [6], rehabilitation and fitting [7, 8], etc. In these applications, high sensitivity and large workable range are major concerns. However, most of published results so far only have strain sensitivity in the range from 1 to tens. The report on further improving the sensitivity of conductive fabrics is very limited. In this study, we will report our recent program on electrically conducting nylon/polyurethane fabric, placing an emphasis on its performance and mechanisms for sensing strain. Experimental The commercial Polycaprolactam (PA6) multi-filaments with a triangle profile in 702 denier/68F and polyurethane (PU) fibers (Lycra™) in 40 denier were supplied by Dupont. PA6/PU plain knitted fabric was from Sunikorn Knitters Limited (HK). The fabric architecture is a weft plain knitted structure manufactured by a plating technique, as shown in Fig. 1. Pyrrole (99%) and FeCl3·6H2O (used as an oxidising agent) were supplied by Sigma-Aldrich Chemical Company. Sodium dodecyl benzene sulphonate from the same supplier was used as a doping agent.
Fig. 1 Weft plain knitted structure by plating technique
The conductive fibers or fabric was prepared by vapor phase polymerization of PPy on the surface of fibers under the temperature of -26oC with vacuum environment for 72 hours. After drying, an annealing process was followed by heating the fibers or fabrics at 60 oC for 20 hours under vacuum. The electrical resistance of the PPy-coated fibers or fabric was measured by a four-probe method with a Keithley 2010 Multimeter while specimens were extended. The load and deformation were recorded using an Instron testing system (Model 4466). For cyclic tension, specimens were repeatedly stretched and recovered in 10 cycles with a maximum strain up to 50%. In-situ tensile tests in a scanning electron microscope (SEM, Lecia Steroscan 440) were conducted for both PPy-coa
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