Biodegradable Tactile Sensors Using a Bioderived Ionic Liquid for Transient Ionics

Ionic skin is a fundamental platform for tactile sensors that utilize electrolytes as sensing components. Ionic liquids (ILs) are ideal for such applications because of their high ionic conductivities, wide potential windows, and negligible vapor pressures. However, their toxicity hinders their use in wearable, implantable, and environmentally sensitive devices. Herein, ionic gels are synthesized from a bioderived IL and comprise pyramidal microstructures that enhance their tactile sensing capability. These structures improve elasticity and reduce the intrinsic viscoelasticity of the gels. The optimized sensor exhibits two conductance sensitivities of 0.066 and 0.032 and capacitive sensitivities of 0.075 and 0.042 in the pressure ranges of 0-10 kPa and 10-50 kPa, respectively. It exhibits rapid response and relaxation times of 156 and 157 ms, respectively, and maintains sensing capabilities for more than 5000 mechanical cycles, with a change in the conductance of only 8.6%. The sensor degradation test revealed that the active componentsthe ionic gel and molybdenum (Mo) electrodesdegraded in phosphate-buffered saline within 133 days, whereas the substrate and encapsulation layer remained nondegradable under the tested conditions. These results demonstrate the potential of biodegradable, nontoxic tactile sensors prepared using bioderived ILs in healthcare monitoring, wearable electronics, and environmental sensing.