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

• Published in: Materials horizons 2024-03, Vol.11 (6), p.1495-151
• Main Authors: Norikane, Yasuo, Ohnuma, Mio, Kwaria, Dennis, Kikkawa, Yoshihiro, Ohzono, Takuya, Mizokuro, Toshiko, Abe, Koji, Manabe, Kengo, Saito, Koichiro
• Format: Article
• Language: English
• Subjects: Azo compounds; Contact angle; Controllability; Droplets; Fluorescence; Light; Light irradiation; Light sources; Quantum dots; Translational motion
• ISSN: 2051-6347; 2051-6355
• DOI: 10.1039/d3mh01774e

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 μm moved with a maximum velocity of 300 μm 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° or 35°, 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.