A tri-modal tactile sensor based on porous ionic hydrogel for decoupled sensing of temperature and pressure

Developing simple device configurations to satisfy independent thermal and force sensing is critical for improving the recognition and manipulation capabilities of robotic hands on objects, but it remains a challenge. In this paper, through the composition adjustment of polyvinyl alcohol, KOH, nano-silica, glycerin, and the microporous structure design, the prepared ionic hydrogel sensor has promising comprehensive performance. It shows thermal sensitivity (−0.47 % °C −1 , 0–20 °C; −0.24 % °C −1 , 20–50 °C), pressure sensitivity (1 kPa −1 , 0–300 kPa), pressure detection limit of 1 Pa, and mechanical durability (1000 compression fatigue cycles at 100 kPa). More importantly, the pressure-sensitive and thermal-sensitive properties hardly interfere with each other due to the ionic hydrogel network's synergy of excellent water retention, anti-freezing properties and heat insulation ability. The multifunctional tactile sensor is integrated into a robot hand to obtain force and thermal information of the measured object, and combined with machine learning algorithms to realize object recognition. The proposed sensing scheme has been applied to 6 kinds of fruit and vegetable classification tasks in a cold chain logistics scenario, showing a classification accuracy of 95 %.