Photo-controllable azobenzene microdroplets on an open surface and their application as transporters

The control of droplet motion is a significant challenge, as there has been no simple method for effective manipulation. Utilizing light for the control of droplets offers a promising solution due to its non-contact nature and high degree of controllability. In this study, we present our findings on the translational motion of pre-photomelted droplets composed of azobenzene derivatives on a glass surface when exposed to UV and visible light sources from different directions. These droplets exhibited directional and continuous motion upon light irradiation and this motion was size-dependent. Only droplets with diameters less than 10 mu m moved with a maximum velocity of 300 mu m min-1. In addition, the direction of the movement was controllable by the direction of the light. The motion is driven by a change in contact angle, where UV or visible light switched the contact angle to approximately 50 degrees or 35 degrees, respectively. In addition, these droplets were also found to be capable carriers for fluorescent quantum dots. As such, droplets composed of photoresponsive molecules offer unique opportunities for designing novel light-driven open-surface microfluidic systems. Photoresponsive microdroplets exhibit directional and continuous movement on a glass surface when simultaneously irradiated with two different light sources. Additionally, these droplets function as carriers for fluorescent quantum dots.