Leaf vein-inspired photothermal actuator balances speed, strength and stability

A recent breakthrough in photothermal actuator design has been achieved by a research team from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, led by Prof. Tian Xingyou and Prof. Zhang Xian. The team developed a novel superstructure liquid metal/low expansion polyimide/polydimethylsiloxane (LM@PI/PDMS) actuator, which combines rapid movement with impressive load-carrying capacity—an achievement that has eluded previous actuator designs.

“The design mimics the structure of leaf veins,” said Li Xiaofei, a member of the team, “which balances the strength and speed of the actuator.”

The result was published in Advanced Materials.

One of the main challenges in designing photothermal actuators has been the trade-off between response speed and load-carrying capacity. Thin actuators can respond quickly but lack strength, while thicker actuators can carry more weight but are slower. Liquid metal photothermal actuators (LM-based) had previously shown promise but failed to solve this issue, as LM microspheres provided thermal properties without significantly enhancing the strength of the material.

In this study, inspired by the leaf’s microvascular network, the researchers used laser etching to create intricate graphene trenches within the LM@PI films. These trenches were then encapsulated with PDMS to produce a programmable actuator that retains both speed and load-carrying capabilities. The leaf vein-inspired structure allows the actuator to respond quickly while maintaining strength and durability.

The new actuator design combines the fast response of lightweight materials with the load-carrying strength of thicker ones. The team demonstrated the potential of these actuators by creating a photo-activated robotic dog capable of crawling, jumping, swimming, and standing, as well as single-pole triple-throw switches and high-speed oscillators.

By introducing superstructures into the design, this research opens up new ways for designing actuators that are faster, stronger, and more versatile, with wide-ranging applications in robotics and intelligent systems.