Light-powered artificial muscle works in water

Dr. Hyun Kim at the Korea Research Institute of Chemical Technology (KRICT), Prof. Habeom Lee at Pusan National University, and Prof. Taylor H. Ware at Texas A&M University developed the artificial muscles based on azobenzene-functionalised semicrystalline liquid crystal elastomers (AC-LCEs) that actuate in response to light.

Traditional soft robotic actuators driven by electricity, heat, or pneumatic and hydraulic systems are often challenging to operate in underwater environments due to the exposure of components like batteries, motors, wires, or pumps to water.

While photothermal materials have been proposed, achieving shape changes underwater remains challenging due to concurrent cooling effects, which has so far restricted their use. Existing photochemical actuators have also been mainly reported as performing simple bending motions, as molecular-level structural changes only occur near the surface.

To overcome these limitations, the team designed AC-LCEs with enhanced stiffness and controlled structures. By incorporating azobenzene molecules into a specifically engineered liquid crystal elastomer, they created materials that contract or expand when irradiated with UV or visible light, respectively. Unlike most photothermal or electrothermal systems, these materials can temporarily retain their deformed state even after the light is turned off, enabling a ‘latch-like’ locking mechanism that allows for sequential and spatial control of motion.