Sensitively Humidity-Driven Actuator and Sensor Derived from Natural Skin System

Abstract

Precise control over the smart materials exhibiting reversible shape changes in response to environmental stimuli presents a considerable challenge. Here, with a self-assembly strategy by extracting natural materials from pigskin, a single layer bio-inspired, transparent, soft biological film (BF) with the primary characteristics of self-actuation and self-sensing is successfully developed. The self-assembly constructed BF can exchange water and reflect environmental humidity gradients rapidly to activate continuous rotary movement. Temperature which affects the thermal motion of water molecules will induce different orientation movement of the film, and on this basis, a humidity-driven energy transfer motor is developed. More characterizations highlight the behavior mechanism of BF through water exchanging by a hydrogen bonding interaction with the hydrophilic group of amino acids residues on the BF surface. Finally, a wearable, steady and ultrafast-response sensor to detect human breathing, especially for real-time obstructive sleep apnea (OSA) state, is fabricated. This study offers great potential in emerging applications including micro-sensors, switches, soft robots and power source technologies.

Keywords: biomaterial, denatured collagen, humidity gradient, humidity driven sensor, breathing monitor