Graphene assisted ion-conductive hydrogel with super sensitivity for strain sensor

Hydrogels flexible wearable sensors have gained widespread attention. However, there was a great challenge to prepare the flexible hydrogel sensor with rapid response, wide strain monitoring ranges, great sensitivity and self-adhesion. Therefore, the greatly sensitive and rapidly responsive strain sensor with wide monitoring range and self-adhesion was prepared by introducing sodium caseinate (SC) and reduced graphene oxide (rGO) into the polyacrylamide hydrogel due to ions and electrons provide two different ways of conducting electricity. Casein not only imparted excellent adhesion to the hydrogel, but also provided a good ionic conductive pathway. In addition, the introduction of rGO could offer an electronic pathway. Therefore, the obtained hydrogel exhibited excellent rapid response (190 ms), high sensitivity (Gauge factor, GF = 13.14) and wide strain monitoring range (0.1–1100%). As a result, SC/rGO/PAAm hydrogels could detect sensitive locomotor signals (for example speaking) and large-scale mankind movements for example knee bending). It was believed that the ion and electron conduction would provide a new mechanism to preparing greatly sensitive hydrogel strain sensor.