Highly transparent, adhesive, stretchable and conductive PEDOT:PSS/polyacrylamide hydrogels for flexible strain sensors

With increasing interest and demand for wearable electronics and healthcare devices, fabricating a conductive hydrogel sensor combining high transparency, self-adhesion and toughness is necessary but remains challenging. In this paper, we developed transparent, adhesive, stretchable and tough hydrogels via semi-interpenetrating network (SIPN) strategy. The SIPN consists of linear poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and chemically cross-linked poly(acrylamide-co-methacrylic acid). Here, methacrylic acid was used to improve the self-adhesion, tensile properties and the electrical conductivity of the hydrogel. The fabricated hydrogels exhibit high transparency, robust adhesion to various substrate surfaces as well as skin, relative high stretchability and tensile strength. Furthermore, the hydrogel also exhibits excellent linear response as a flexible strain sensor to detect human motions and tiny physiological signals. It is envisioned that the SIPN strategy and the introduction of methacrylic acid provide a new way for developing high performance conductive hydrogel for strain sensors.