https://www.sciencedaily.com/releases/2018/06/180604112518.htm

A mechanical engineering team led by Professor Alfonso Ngan Hing-wan, Chair Professor in Materials Science and Engineering, and Kingboard Professor in Materials Engineering, Faculty of Engineering, the University of Hong Kong (HKU) published an article in Science Robotics on 30 May 2018 (EST) that introduces a novel actuating material -- nickel hydroxide-oxyhydroxide -- that can be powered by visible (Vis) light, electricity, and other stimuli. The material actuation can be instantaneously triggered by Vis light to produce a fast deformation and exert a force equivalent to 3000 times of its own weight. The material cost of a typical actuator is as low as HKD 4 per cm2 and can be easily fabricated within three hours.