Broad‐Wavelength Light‐Fueled Organic Crystal Oscillators Driven by Multimodal Photothermally Resonated Natural Vibration

Photomechanical crystals have applications in light‐fueled actuators and soft robots. Herein, light‐responsive, versatile, anthraquinone dye crystal oscillators actuated via natural vibrations that are resonated by a photothermal effect are described. A black needle‐shaped crystal cantilever oscillates at 70 Hz in the first mode of natural vibration upon irradiation by broad‐wavelength light ranging from the ultraviolet through the visible to the near‐infrared, and also under continuous‐wavelength light (400–2000 nm). The second and third natural vibration modes are induced at higher frequencies (530 and 1350 Hz) and evidence complex flagellum‐like motions. The frequency can be readily tuned by moving the support of a crystal piece; this is analogous to playing a guitar. The crystal exhibits high durability (more than 10 000 cycles): the high elasticity prevents deterioration. Oscillatory motions can be designed via simulations using finite element analysis. This work will facilitate the use of photomechanical crystals in light‐fueled soft robots. Light‐fueled organic crystal oscillators driven by photothermally resonated first, second, and third modes of natural vibration are developed. The oscillators operate under broad‐wavelength light including ultraviolet, visible, near‐infrared, and continuous‐wavelength light. The frequency can be easily tuned by moving a support, just like playing a guitar. The oscillators demonstrate high durability and power densities.