Intelligent Silk Fibroin Ionotronic Skin for Temperature Sensing

The emergence of ionotronic materials has substantially extended the applications of artificial skins by allowing intimate interfaces between electronics and biological/bionic surfaces toward achieving improved sensing and communication with surrounding stimuli. However, ionotronic skins are intrinsically temperature dependent, since water molecules play crucial roles in regulating both mechanical and ionic conductivity of the materials. Hence, most of the ionotronic skins will fail at temperatures below 0 degrees C. In this study, a highly sensitive ionotronic skin that can be used in the entire natural environmental temperature range (-30-80 degrees C) is developed by using silk fibroin and Ca(II) ions as starting materials. In such a system, silk fibroin serves as both structural supports and ion capture agent to provide structural stability, mechanical flexibility, and interfacial adhesion ability, while Ca(II) ions work as ionic conductor, hygroscopic agent, and deicing salt to offer highly stable ionic conductivity at a temperature range from -30 to 80 degrees C. These synergetic merits, together with favorable advances of silk fibroin ionotronic skins in biocompatibility, transparency, and self-healing, allow them to be used in multiple emerging fields, such as regenerative medicine, implantable electronics, and human-machine interface.