Water-repellent flexible fabric strain sensor based on polyaniline/titanium dioxide-coated knit polyester fabric

A flexible fabric strain sensor was prepared by in situ chemical polymerization of aniline on knit polyester fabric surface in aqueous acid solutions using ammonium persulfate as an oxidant. Furthermore, the optimum addition ratio of titanium dioxide (TiO2) in polyaniline (PANI) in the granular conductive network membrane was investigated. The morphological, structural, thermal, electrical, strain-sensing, and water-repellent properties of the polyester knit fabrics modified with PANI and PANI/TiO2 hybrid were analyzed. The surface electrical resistance of PANI/TiO2 conductive films on the knit fabric was higher than that of pristine PANI, which was due to the particle blocking the conduction path effect caused by TiO2 embedded in the PANI matrix. However, it was further found that the addition of TiO2 could improve the durability properties of flexible fabric strain sensor against cycles of elongation, though with a little loss in electrical conductivity and sensitivity. Moreover, the water-repellent property was evaluated by measuring water contact angles. The results showed that for PANI/TiO2 nanocomposites-coated flexible fabric strain sensor, a desirable level of contact angle (127.5 degrees +/- 1.7 degrees) was even preserved at 121.8 degrees +/- 2.6 degrees after 100 cycles of elongation. This indicated that the flexible fabric strain sensor had rather high water-repellent efficiency and excellent durability during the elongation cycles.