A phototactic liquid micromotor

Abstract

In recent years, micromotors, which possess unique autonomous moving properties inside a solution, have shown great potential in a variety of applications ranging from environmental remediation to the biomedical field. However, most of the micromotors are based on solid materials. In this paper, we report a liquid (water, serum or urine) micromotor, which exhibits self-propelling behavior in an oil solution upon white light irradiation. Interestingly, the liquid micromotor exhibits both positive and negative phototaxis, which relies on the photochromism of the surrounding spiropyran molecules dissolved in oil or the thermal effect, respectively. In addition, light shows great versatility in controlling the motion behavior of the liquid micromotor so that it can move in a desired fashion. Furthermore, we have demonstrated that the liquid-based micromotor has great advantages over the solid ones. It not only enables fusion and reaction between different reactant-loaded liquid micromotors based on the combined positive and negative phototaxis, but also allows controlled cargo capture and transportation. We thus believe the liquid micromotor reported in the current study may have potential applications in various fields such as glucose detection.