Carbon Nanotube-Based Hierarchical Paper Structure for Ultra-high Electrothermal Actuation in a Wide Humidity Range

Abstract

The hierarchical structure of multiwalled carbon nanotubes (CNTs), cellulose paper, and the polydimethylsiloxane (PDMS) polymer is realized for a low-power-driven actuator capable of operating under various humidity conditions. The highly conducting and flexible CNT network is attributed to Joule heating-controlled hygroexpansion of cellulose paper and thermal expansion of PDMS. The study showed an ultrahigh actuation of 1.4 cm with a 0.95 cm–1 bending radius of curvature at a much lower power density of 35 mW mm–3. Operation over multiple cycles shows the large durability of the device and its potential application in soft robotics as a soft weightlifter. The actuator is shown to be capable of lifting 525% more than its weight up to a height of 1 cm. The experimental result was validated using analytical modeling. Furthermore, our results suggest that these actuators can be operated both in dry and in variable moist environments, which makes it applicable in various fields including microrobotics, artificial muscles, microsensors, microtransducers, micromanipulators, microvalves, and so on.