Light-Controlled Micromotors and Soft Microrobots

Mobile microscale devices and microrobots can be powered by catalytic reactions (chemical micromotors) or by external fields. This report is focused on the role of light as a versatile means for wirelessly powering and controlling such microdevices. Recent advances in the development of autonomous micromotors are discussed, where light permits their actuation with unprecedented control and thereby enables advances in the field of active matter. In addition, structuring the light field is a new means to drive soft microrobots that are based on (photo-) responsive polymers. The behavior of the two main classes of thermo- and photoresponsive polymers adopted in microrobotics (poly(N-isopropylacrylamide) and liquid-crystal elastomers) is analyzed, and recent applications are reported. The advantages and limitations of controlling micromotors and microrobots by light are reviewed, and some of the remaining challenges in the development of novel photo-active materials for micromotors and microrobots are discussed.