Microfluidic Induced Controllable Microdroplets Assembly in Confined Channels

Abstract

We report on the microfluidic induced monodispersed microdroplet generation and assembly in confined microchannels. Two and three dimensional close-packed droplet lattices were obtained in microfluidic devices by adjusting the channel geometry, the fluidic flow rates and the monodispersed droplet size. The droplet packing was mainly caused by the volumetric effect and capillarity in confined microchannels. Polymerizable fluids were also investigated to demonstrate the effect of fluidic properties on the microdroplet generation and assembly, which could find interesting applications in the future. This approach would be helpful to fundamentally understand the mechanism of self-assembly process of particles in confined microstructures, and practically be applied in sensing and energy storage devices.

Microfluidic formation of crystal-like structures

“…A potential disadvantage of the systems employed by Hatch et al 33 and by Priest et al 34 is that the formation of the 3D crystal was delayed by the presence of the continuous phase that needed to be replaced by new droplets. A way around this problem has been proposed by Wang et al 40 and then significantly optimised by Parthiban et al 35 Wang et al 40 simply added some tiny lateral channels to the expansion region with the goal of removing the continuous phase, thus 'accelerating' the formation of the 3D droplet crystal. They employed a microfluidic device with constant height h = 50 μm where water-in-oil droplets were formed using a flow-focusing geometry: the droplets then reached an expansion area where strong hydrodynamic interactions took place, facilitated by the removal of the oil via the lateral channels.…”

“…As previously discussed, one way to drive the formation of compact droplet crystals is to remove the continuous phase in the expansion chamber. 35,40 By following this procedure, O'Keefe et al 45 enhance the formation of a 2D crystal and ii) immobilise each droplet in a single place (Fig. 5c).…”

Controlled open-cell two-dimensional liquid foam generation for micro- and nanoscale patterning of materials

“…1c). The 2D natural foam is generated with a common design of a droplet microfluidic device 29 . First, the micropost array in the engineered 2D liquid foam pins the films between the nearby microposts for ease of manipulation in subsequent patterning applications.…”

Droplets as Carriers for Flexible Electronic Devices

“…The droplets can adaptively and reversibly alter their geometry to accommodate the surrounding environment, while maintaining their functionality through intact flexible electronic devices. The ADs reveal new types of deformable artificial organism that can be miniaturized and organized to complete time‐consuming and labor intensive assignments, such as gene‐expression analysis, chemical synthesis, drug discovery, and microassembly that demand complicated liquid operations and continuous monitoring. The ADs can also be deployed in large scales to offer collected efforts in monitoring environmental conditions and pollutants, or even charging localized environments.…”