A biodegradable ionic gel for stretchable ionics

Gel electrolytes are a promising material in the field of electronics, energy, and wearable devices due to their preferrable physical and electrochemical characteristics such as non-volatility, relatively large potential window, and high ionic conductivity. Ionic gels, however, possess toxicity that would potentially pollute environment and hinder application for environmental sensing. Decomposability and moderate toxicity are therefore required for disposable use. In this work, we develop a biodegradable ionic gel (BDiG) using a poly(ethylene glycol) diacrylate (PEGDA) combined with a biodegradable ionic liquid, 1-Butyl-3-methyl-Imidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][TFSI]). The developed BDiG exhibites mechanical flexibility of fracture strain upwards of 300% and Young's modulus of 14 kPa. Electrical characteristics of the BDiG were a potential window of 4.8 V, ionic conductivity of 3.1 mS cm-1, and electrical double layer capacitance of 34 & mu;F cm-2 when 90% weight ratio of ionic liquid was used. A tactile sensor is demonstrated as a proof of concept of ionic skin, whose electrical conductivity increases linearly with the pressure.