Highly transparent RCF/PTFE humidity and IR light dual-driven actuator with high force density, sensitivity and stability

Abstract

Transparent actuators have received great interest among researchers due to their potential applications in tactical displays, optical switches, zoom lenses, etc. In this work, we designed and developed a highly transparent cellulose-based actuator, made of regenerated cellulose film (RCF) and hydrophobic polytetrafluoroethylene (PTFE) two-layered film, which was fabricated by using a simple sputtering method to grow PTFE film on the RCF film. The RCF/PTFE actuator exhibits high sensitivity towards both humidity- and IR light-driving responses, which can be attributed to thermal expansion and hygroscopic expansion differences between RCF film and PTFE film. The stability of the actuator was greatly improved by O plasma etching of the RCF film surface. Bi-directional actuation of the actuator can be achieved by controlling the ambient humidity and IR light irradiation, with the bending angle changing from 0° to 360° within 14 s and 10 s, respectively. Numerical simulations show that the sensitivity and stress of RCF/PTFE actuators are more than one order of magnitude higher than petroleum-based actuators, which can be attributed to the unique hygroscopic effect of cellulose. The as-obtained actuator may have potential applications in the fields of smart window, bionic robot, optical devices, sensing and camouflage.