Bioinspired flexible, breathable, waterproof and self-cleaning iontronic tactile sensors for special underwater sensing applications

Flexible tactile sensors are under high pursuit for wearable healthcare devices. However, challenges still exist in achieving both wearing comfortability through air permeability and hydrophobicity to resist water splash or even to be used in the special underwater circumstance. Inspired by the smart bio-structure of lotus leaf, we develop a flexible, breathable, waterproof and self-cleaning tactile sensor by sandwiching one ionogel electrolyte between two polydopamine (PDA)/MXene/stearic acid (STA) fabric electrodes. The micro-channels in the fabric and the through-holes in the gel endow the sensor with a high air breathability of 723.5 mm s−1 and the STA micro-sheets decorated on the outside surface of the sensor provide hydrophobicity with a large water droplet contact angle of 140.7° for the unique properties of self-cleaning and washability. By taking advantage of the supercapacitive sensing mechanism, the microstructures of MXene nanosheets on microfibers and the using of an interlayer with an internal aperture to initially separate electrodes and electrolyte, an extremely high sensitivity of up to 1677.79 kPa−1 is achieved. Practical sensing applications of the developed flexible sensors worn on different parts of human body for physiological signal monitoring, motion detection and silent information communication through Morse code in the special underwater circumstance are demonstrated.