Very Wide Sensing Range and Hysteresis Behaviors of Tactile Sensor Developed by Embedding Soft Ionic Gels in Soft Silicone Elastomers

We present fabrication and characterization soft tactile sensors composed of ion gel channel and elastomer (ion gel/elastomer sensors) and compared the sensing properties of the ion gel/elastomer sensors with ionic liquid/elastomer sensors. We have studied the relationship between the impedance and current frequency for the sensors. The impedance of the conductive channels surrounded by the elastomer is drastically decreased with increase in the current frequency in lower frequency regime and the impedance is approximately constant in the higher regime. We evaluated the change in impedance of the sensors against mechanical stimuli. It is observed that the optimum detection range of ionic liquid/elastomer sensor is 0–21 kPa of normal load, while the optimum detection range of the ion gel/elastomer is 0–510 kPa of the normal load. In addition, we investigated the effect of thickness of elastomer surrounding ion gel on impedance profile in response to applied normal pressure. The hysteresis of the relationship between the impedance change and the applied pressure is observed in loading and unloading procedures in the case of 3-mm thickness sensors while the hysteresis of the relationship between the impedance change and the strain is observed in the case of 6-mm thickness sensors.