An interpenetrating-polymer-network-based tough ion gel with high humidity resistance for sensitive human motion detection

Abstract

A transparent and stretchable tough ion gel with high humidity resistance was fabricated by constructing a hydrophobic interpenetrating polymer network (IPN) in a hydrophobic ionic liquid (IL). Remarkably, the IPN ion gel with impressive 80 wt% IL content displayed high fracture stress of 611 kPa and fracture strain of 219%, and these good mechanical properties could be maintained even at a high relative humidity (RH) of 90%. The self-recovering ratio of the mechanical strength of the IPN ion gel could reach 95.6%. The ionic conductivity of the IPN ion gel under humidified conditions with RH of 90% was as high as 2.7 mS cm⁻¹. The IPN ion gel also demonstrates a wide temperature tolerance range (–48 to 300 °C), almost zero IL leakage under mechanical stress of 108 kPa for 72 h, good adhesion ability, low cytotoxicity, and high antibacterial ability. These superior characteristics collectively render the ion gel highly effective when utilized as a strain sensor for detecting human motions. Both large and small movements of the human body could be clearly monitored and showed good distinctiveness, repeatability, and long-term stability even at 90% RH. This study is expected to advance the development of conductive, stretchable tough ion gel sensors with excellent humidity resistance for harsh application environments.