Ferroelectric BaTiO3 Freestanding Sheets for an Ultra-High-Speed Light-Driven Actuator

Light-driven actuators convert optical energy into physical motion. Organic materials, commonly used in light-driven actuators thus far, suffer from two limitations: slow repetitive operation and the requirement of two different light sources. Herein, we report a high-speed, light-driven actuator that can be operated by a single light source with low-energy density. We achieved this breakthrough by utilizing a freestanding epitaxial sheet of ferroelectric BaTiO3. One repetitive operation takes only 120 mu s, which is 10(4) times faster than that of organic-based counterparts. The high-speed operation is derived from the light-induced nonthermal deformation provided by the excellent ferroelectricity (remnant polarization of 23 mu C/cm(2)) and piezoelectricity (d(33) of 600 pm/V) of the sheet. The displacement-to-length ratio is achieved to be 3.7% with a relatively low laser power density (10-200 mW/cm(2)) compared to previously reports (150-10(9) mW/cm(2)). Furthermore, the actuator was operable even in water, demonstrating its potential in various applications.