Photothermomechanicaly Efficient, Low-Cost, High-Cycle-Life, Hybrid MXene-Polymer Actuators

Abstract: Photothermomechanical polymer film actuators stand out among the dynamic components available for soft robotics due to a combination of assets, such as capability for rapid energy transduction, wireless control, and ease of miniaturization. Despite their anticipated superior performance, several design challenges remain. These include high operational temperatures, inadequate mechanical output relative to the radiation energy provided, limited durability during repeated use, and high production costs; such factors hinder the scalability of these actuating materials in practical applications. Here, we report a viable solution by substituting performance-enhancing nanoparticles with MXenes--carbon-based, two-dimensional materials known for their theoretical photothermal conversion efficiency of up to 100%. This led to the development of MXene-dispersed polymer trilayer actuators (MPTAs). Extensive photothermal and thermomechanical characterization demonstrated superior performance compared to previously reported actuators, with a reduced shed power demand (0.1 mW cm$^{-2}$ $^\circ$C$^{-1}$), substantial bending capacity per irradiation power per time (0.1$^\circ$ mW$^{-1}$ cm$^{2}$ s$^{-1}$), and enhanced cyclic longevity, with fatigueless operation of at least 1,000 cycles. We demonstrate three applications: A kirigami-inspired flower, parallel manipulator, and soft gripper. Additionally, these materials are cost-effective; thus, they are the optimal choice for long-term, reversible operation with efficient heat-to-work transduction.