Solar Spectrum Light-Driven Silicone-Based Fluidic Actuators

Soft materials that convert light into mechanical energy can create new untethered strategies for actuating soft robotics. Yet, the available light-driven materials are often incompatible with standard fabrication in soft robotics and restricted to shapes (e.g., sheets) that have limited capability for 3D deformation; often laser or focused light is required for actuation. Here, to address these challenges, a straightforward method for synthesizing sunlight-responsive fluidic actuators from off-the-shelf silicone precursors capable of expanding in 3D is developed. A liquid phase and activated carbon as photothermal elements are constrained in the elastomer. Solar spectral light triggers a liquid–gas phase transition creating sufficient pressure to overcome the internal elastic stress and actuate the material. The fluidic actuation is characterized under varying light conditions reaching expansion cycle times between ≈20–500 s, strains of 28%, and actuation stress of ≈1.3 MPa in different experiments. The materials were then used to exemplarily drive a mechanical switch, a liquid dispensing soft pump, a valve, and a bending actuator. As the described materials are easy to produce in a 5 min synthesis by standard molding techniques, it is believed that they are a promising opportunity for embodied energy converters in environmentally powered soft robots that respond to sunlight.