Light-driven rotary polypyrrole/agar composite films

Light-driven rotary actuators have undergone tremendous progress in recent years and show great potential for different applications ranging from sensors, soft robots to micro–nano intelligent systems. However, most photoactuators with rotary motions have a low rotational speed due to their low responsive speed and small driving force, which hinder both their fundamental and practical research. In this paper, we report a fast rotation of a soft actuator in response to light, which harnesses the synergistic interactions between two binary responsive components, i.e. water responsive agar and photothermally responsive polypyrrole, leading to a structural protrusion at the irradiation center that provides a jet-propulsion when the gas expands to the edge of the film. Interestingly, the motion behavior of the photoactuator film could be well controlled from the in-place rotation to horizontal motion as a result of the fast rotation with a speed as high as 5200 rpm. The current study indicates a fast rotation could be realized by the simple design and fabrication, which may not only stimulate the exploration of new motion behaviors for photothermal actuators but also open up new opportunities for their practical applications.