Moving Droplets in 3D Using Light

• Published in: Advanced materials (Weinheim) Vol. 30; no. 35; pp. e1801821 - n/a
• Main Authors: Xiao, Yang, Zarghami, Sara, Wagner, Klaudia, Wagner, Pawel, Gordon, Keith C., Florea, Larisa, Diamond, Dermot, Officer, David L.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 29.08.2018
• Subjects: Additives; Chemical reactions; chemical transport; Droplets; interfacial tension; Light sources; Marangoni effect; Nuclear fuels; Organic chemistry; photoactive microdroplets; spiropyran; Surface tension; Three dimensional motion; Transport; Vesicles; spiropyran; interfacial tension; Marangoni effect; photoactive microdroplets; chemical transport
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.201801821

The emulation of the complex cellular and bacterial vesicles used to transport materials through fluids has the potential to add revolutionary capabilities to fluidic platforms. Although a number of artificial motile vesicles or microdroplets have been demonstrated previously, control over their movement in liquid in 3D has not been achieved. Here it is shown that by adding a chemical “fuel,” a photoactive material, to the droplet, it can be moved in any direction (3D) in water using simple light sources without the need for additives in the water. The droplets can be made up of a range of solvents and move with speeds as high as 10.4 mm s−1 toward or away from the irradiation source as a result of a light‐induced isothermal change in interfacial tension (Marangoni flow). It is further demonstrated that more complex functions can be accomplished by merging a photoactive droplet with a droplet carrying a “cargo” and moving the new larger droplet to a “reactor” droplet where the cargo undergoes a chemical reaction. The control and versatility of this light‐activated, motile droplet system will open up new possibilities for fluidic chemical transport and applications. The light‐controlled isothermal 3D movement in water of organic droplets containing a photoactive material is demonstrated. The droplets can be moved toward or away from light and can be merged with other droplets to pick up “cargo” that can undergo a chemical reaction through droplet–droplet interactions.