An elastomeric ionic hydrogel sensor for large strains

An elastomeric hydrogel membrane made of an epoxy-amine network is demonstrated to be a linear strain sensor for large strains up to 20%. Sodium chloride is added in the gel to maintain conductivity at a relatively dry state. The elastic and electrical response are both shown to be linear. Water loss from the hydrogel due to evaporation from the surface is slow. This results in a trend in the impedance of the sensor which can be easily corrected by simple signal processing. A prototype sleeve that uses these sensors for proprioceptive sensing of joint angle motion on a robotic arm is demonstrated as a potential application.