Transportation of Nano/Microparticles via Photoinduced Crawling of Azobenzene Crystals

The stimulus-driven motion of microscale objects on solid surfaces is a promising process to realize the manipulation of microdroplets, which has applications in fields areas such as material accumulation and sensing at a micro level. Light is an effective external stimulus for object manipulation because it can provide contactless spatial and temporal control. In this study, a new method is devised to transport nano/micromaterials on a glass surface by exploiting the photoinduced crawling motion of crystals. 4-(methylamino)azobenzene (4-MAAB) crystals are used to transport nano/micromaterials via photoirradiation from a single visible-light source without using expensive equipment such as lasers and positioning devices. Nano/micromaterials mixed with the 4-MAAB crystals are successfully transported with the crawling 4-MAAB crystals. The nano/micromaterial transport is tracked using the fluorescence from the nano/micromaterials embedded into the 4-MAAB crystals. In situ time-resolved X-ray diffraction measurements are also conducted for mechanistic analysis. This study offers new development paths in fields such as microfluidics and microrobotics.