Photothermally induced natural vibration for versatile and high-speed actuation of crystals

The flourishing field of soft robotics requires versatile actuation methodology. Natural vibration is a physical phenomenon that can occur in any material. Here, we report high-speed bending of anisole crystals by natural vibration induced by the photothermal effect. Rod-shaped crystal cantilevers undergo small, fast repetitive bending (similar to 0.2 degrees) due to natural vibration accompanied by large photothermal bending (similar to 1 degrees) under ultraviolet light irradiation. The natural vibration is greatly amplified by resonance upon pulsed light irradiation at the natural frequency to realise high frequency (similar to 700 Hz), large bending (similar to 4 degrees), and high energy conversion efficiency from light to mechanical energy. The natural vibration is induced by the thermal load generated by the temperature gradient in the crystal due to the photothermal effect. The bending behaviour is successfully simulated using finite element analysis. Any light-absorbing crystal can be actuated by photothermally induced natural vibration. This finding of versatile crystal actuation can lead to the development of soft robots with high-speed and high-efficient actuation capabilities.

Automated summary

This paper reports the high-speed bending of anisole crystals using natural vibration induced by the photothermal effect. The bending behavior is greatly amplified through resonance to achieve high frequency, large bending, and high energy conversion efficiency. Any light-absorbing crystal can be actuated by the photothermally induced natural vibration. This versatile crystal actuation method can contribute to the development of soft robots with high-speed and high-efficiency actuation capabilities.