Multi‐Hierarchically Porous SWNTs‐TPU/C‐WPU Composite Film for Underwater Self‐Powered Multi‐Modal Tactile Information Sensing

Obtaining multi‐mode tactile information with one sensor in deep sea is greatly needed yet still challenging. In this paper, a flexible deep sea tactile sensor is reported, capable of detecting object's conductivity, hardness, pressing pressure and position simultaneously just by one touch. The sensor works by using single‐walled carbon nanotubes doped thermoplastic polyurethane elastomer (SWNTs‐TPU film) for differentiating object's conductivity based on the work function difference induced electron transfer. A porous anionic aliphatic waterborne polyurethane film containing carboxyl functional groups (C‐WPU) is used for generating ionic currents under pressing to determine the pressing pressure and position and recognize the relative hardness of an object. It is found that the magnitude of current signal generated by a metallic object is much larger than that of an insulative object. The signal magnitude increases with the increase in the applied pressure, the pressing area and the film thickness. Furthermore, completely encapsulating the C‐WPU film and introducing carboxylic functional groups significantly improve the sensitivity (maximum 1.2 kPa−1). The response time and recovery time of sensing signals are 150 and 530 ms respectively. A pressure detection range of 45–625 kPa is achieved, with a pressure detection resolution of 9.2 kPa. The signal magnitude is decreased only by 10.54% when the sensor is placed under a simulated 100 m water depth. Proof of concept demonstration of underwater object discrimination and hardness recognition with this sensor placed on a mechanical finger of a ROV (Remotely Operated Vehicle) is successfully achieved. This work provides a new solution for multi‐modal tactile information sensing in deep‐sea environment.