Three-Dimensional Graphene Foam and PDMS Composites for High-Performance Electrothermal and Photothermal Actuators

Thermal actuators, which use thermal energy as a driving source to realize mechanical energy output, have a broad application prospect in robotics, precision instruments, biotechnology, and other fields. Three-dimensional (3D) graphene foams (GFs) prepared by chemical vapor deposition (CVD) have unique thermally and electrically conductive network/skeleton structures, showing superior performances and greater application potential than two-dimensional (2D) graphene in some fields. The excellent electrothermal and photothermal properties of 3D GFs make them ideal candidates for fabricating high-performance thermal actuators. In this paper, we report for the first time the electrothermal and photothermal actuators based on CVD-prepared 3D GF with a compressed skeleton structure. The proposed bilayer actuator consists of a composite layer of GF and PDMS and a pure PDMS layer (GF@PDMS/PDMS), and the mass fraction of GF in the GF@PDMS composite layer is about 15 wt %. Experiments and finite element simulation confirm the effect of PDMS layer thickness on the actuation effect. The bilayer actuation can produce a bending deformation of nearly 660° in 15 s under 12 V driving voltage and almost 190° in 12 s under 2 W/cm² near-infrared laser irradiation. Interesting applications of this dual-responsive soft actuator, such as bionic octopus soft tentacles, smart curtains, bionic flowers, and liquid tracking robots, are demonstrated. The bionic tentacle can transport objects 4.3 times its weight, and the liquid tracking robot achieves 140°/s rotational motion and 20.3 mm/s linear motion. This work may provide useful insights for developing smart materials based on 3D graphene materials for applications in microactuators, artificial muscles, bionic robots, etc.