Abstract
This paper presents methods for the formation of hollow microcapsules and microlenses using multiphase microdroplets. Microdroplets, which consist of a gas core and an organic phase shell, were generated at a single junction on a silicon device without surface treatment of the fluidic channels. Droplet, core and shell dimensions were controlled by varying the flow rates of each phase. When the organic solvent was released from the organic phase shell, the environmental conditions changed the shape of the solidified polymer shell to either a hollow capsule or a microlens. A uniform solvent release process produced polymeric capsules with nanoliter gas core volumes and a membrane thickness of approximately 3 μm. Alternatively physical rearrangement of the core and shell allowed for the formation of polymeric microlenses. On-demand formation of the polymer lenses in wells and through-holes polydimethylsiloxane (PDMS) structures was achieved. Optical properties of the lenses were controlled by changing the dimension of these structures.
Highlights
With the rapid development of microfluidic and microdroplet technologies, applications for microdroplets have been widely reported in recent years
Fluids used to form the G/O/W droplet were as follows: The gas phase was air, the organic phase was a solution of 5 wt % polystyrene (MW: 250000) in dichloromethane, and the water phase was a solution of 3 wt % polyvinyl alcohol (PVA) in deionized water
We demonstrated that the environmental conditions of the microcapsule/microlens system during its formation affected the gas core volume and the shell membrane thickness
Summary
With the rapid development of microfluidic and microdroplet technologies, applications for microdroplets have been widely reported in recent years. Microdroplets have provided an environment for the uniform and functional synthesis of microcapsules in industrial fields such as textiles [14,15] and cosmetics [16]. They have been used as efficient optical elements for displays [17,18] and detectors [19,20,21]. Polymeric microcapsules have advanced remarkably using microdroplet technologies. Uniform microcapsules have been formed in miniaturized devices, and the functionality of these microcapsules has expanded as a result of new developments in microcapsule synthesis [22,23,24]
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