A janus hydrogel with high strength, adhesive and conductive for wearable strain sensor

Conductive hydrogels that possess strong mechanical performances and outstanding adhesion property have a broad prospect of application. However, it is still a great challenge to reach the good balance between mechanical and adhesive properties. In this paper, we present a simple method to prepare a Janus hydrogel with high strength, adhesive and conductive for wearable strain sensor. Firstly, the GO-TA-P(DMAEMA- AA-AM) hydrogel was fabricated through the copolymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA), acrylamide (AM) and acrylic acid (AA) in the existence of tannic acid and graphene oxide. Then, the obtained GO-TA-P(DMAEMA-AA-AM) hydrogel was cross-linked with Fe 3+ to enhance mechanical properties by immersing into the ferric chloride solution. Finally, the Janus hydrogel was constructed by soaking one side of the hydrogel into ethylenediaminetetraacetic acid (EDTA) solution to achieve coordination-induced chelating Fe 3+ to form an adhesive surface on a tough hydrogel. The Janus hydrogel showed high mechanical strength (fracture stress of 256 kPa, fracture strain of 213 %, Young's modulus of 234 kPa, toughness of 302.8 kJ/m 3 ) and good adhesion (adhesion strength for stainless steel reached 23.5 kPa) properties. In addition, this hydrogel has good sensing properties with high strain sensitivity and stability which displayed great prospects in the field of electronic sensors.