Highly Conductive, Stretchable, Adhesive, and Self‐Healing Polymer Hydrogels for Strain and Pressure Sensor

Abstract Retractable, self‐healing, and conductive hydrogels are widely used as adjustable and wearable sensing materials. Herein, using polyfunctional trypan blue (TB) as a crosslinking agent for both poly(acrylic acid) (PAA) and polypyrrole (PPy), a retractable and self‐healing PAA‐TB‐PPy hydrogel is prepared. The introduction of TB not only improves the water retention capacity of the hydrogel but also helps form a highly interconnected conductive path. It is found that PAA‐TB‐PPy hydrogel shows a high electrical conductivity (15 S m −1 ) which is almost equivalent to the pure PPy hydrogel. Due to the high stability of the semi‐interpenetrating network structure, the elongation at break of PAA‐TB‐PPy hydrogel is more than 750%, along with high mechanical strength and strong adhesion to a variety of solid surfaces. In addition, the hydrogel exhibits high strain and pressure sensitivity with prominent linearity. Importantly, the as‐prepared hydrogel sensor can reliably detect both repetitive large strain and subtle vibration, which makes it a great candidate as wearable electronics for human motion monitoring.