A plastic motor powered completely by light has been developed by the Tokyo Institute of Technology.

Unlike solar-powered motors that use photovoltaic cells to convert light to electric power (this also requires wires and batteries to deliver and store the power), this motor converts light directly into mechanical energy using a belt made of a special elastomer, with a molecular structure that expands or contracts when illuminated, depending on the wavelength of light.

Tomiki Ikeda, leader of the research team at Tokyo Institute of Technology, discovered a plastic compound containing azobenzene would contract when exposed to ultraviolet light, and resume its original shape when exposed to visible light.

Since this discovery in 2003, Ikeda and his team have been working on improving the shape-shifting properties of the material, and have been looking at ways to incorporate the material in a motor to convert light directly into motion.

To test the suitability of the material as a mechanical power source, the researchers coated a polyethylene film with the shape-shifting plastic to create a 0.08mm thick belt, which was then looped around a pair of wheels measuring 10mm and 3mm in diameter. An ultraviolet light was then shone on the belt near to the smaller wheel, while visible light was directed to the belt nearer the larger wheel. This pushed the belt into action. The larger wheel recorded a top speed of 1rpm.

Following 30 hours of tests which involved the belt expanding and contracting every seven seconds, the researchers recorded the film has around four times more elastic strength than human muscle – which remained unchanged for the duration of the tests.