Transparent, highly-stretchable, adhesive, and ionic conductive composite hydrogel for biomimetic skin

Flexible, self-healing hydrogels with a variety of desirable properties are required for artificial skin applications. Here, we report a novel ionic conductive composite hydrogel consisting of polyacrylamide (PAM), a silk sericin (SS) network and NaCl for use on bionic skin. The use of NaCl made the hydrogels good ionic conductors. Intrinsic interactions between the PAM and SS endowed the hydrogel with good mechanical properties, including a high tensile strength of 0.36 MPa and a compressive strength of 0.38 MPa. The ionic hydrogel showed a high transparency of 93%, a high adhesion strength of 52 kPa, and good conductivity. After being fractured, two pieces of the ionic hydrogel were re-bonded without external stimulation, which simulated the self-healing properties of skin after injury. The hydrogel displayed moisturizing and anti-mildew properties after being stored at room temperature for 2 months. These ionic hydrogels may find applications in artificial skin, human–machine interfaces and soft robotics.