In this article, bifunctional polyaniline/polyacrylamide (PANI/PAAm) hydrogel is fabricated. The hydrogel has capacitive performance and can be used for monitoring human motions. The effect of PANI doped with two different acids on the properties of hydrogels was researched. The first type of PANI hydrogel is doped with hydrochloric (HCl) and the second one with p-toluenesulfonic acid (PTSA). One application of these two kinds of hydrogels was prepared to serve as solid electrolytes in supercapacitors with sandwich structure. The sandwich structure was constructed by introducing two PANI film parts reinforced on both sides of the PANI hydrogel. Supercapacitors with sandwich structure possess areal capacitance of 635 mF/cm2 (HCl-PANI hydrogel) and 1022 mF/cm2 (PTSA-PANI hydrogel). In this structure, PANI hydrogel provides channels for ion transport as a solid electrolyte. In addition, the PANI hydrogel can be utilized as the sensitive sensors as well. By employing I-v curve and I-t curve to characterize the performance of the sensor, the hydrogel material can be used as a wearable sensor with sensitivity to slight deformation. This is a sensitive sensor that it can respond to the speed and amplitude of the bending movement of the arm. The effective bifunctional property results indicate that the hydrogel, capacitive and conductive PANI hydrogel has great piezoelectric sensitivity as the sensors, which has become promising materials for wearable sensors and solid electrolytes.
Keywords: Supercapacitor; hydrogel; polyaniline; sandwich structure; sensor.