A tough shape memory hydrogel strain sensor based on gelatin grafted polypyrrole

Developing shape memory hydrogel strain sensors with both high mechanical property and stable electrical performance is a challenge. Here, a hydrogel based on gelatin was reported as a strain sensor. The hydrogel was developed by gelatin grafted polypyrrole, polyacrylamide and tannic acid. The gelatin moieties were exploited to form a water-soluble conductive polymer, endowing the hydrogel with shape memory behavior and addressing the challenge of low conductivity induced by structural inhomogeneity and aggregation of conductive nanomaterials. Tannic acid was introduced to provide hydrogen-bonding and π−π stacking interactions to promote hydrogel mechanical properties. The hydrogel achieved a maximum tensile strength of 1.44 ± 0.11 MPa, maximum toughness of 2581 ± 453 kJ/m3 and maximum conductivity of 0.58 ± 0.10 S/m. Results demonstrated that the hydrogel showed shape memory property and can respond to and discern different motions. This achievement offers an opportunity to facilitate significant shape memory conductive hydrogel strain sensor with both high mechanical property and stable electrical performance.