Microfluidic fabrication of microparticles for biomedical applications

Abstract

Droplet microfluidics offers exquisite control over the flows of multiple fluids in microscale, enabling fabrication of advanced microparticles with precisely tunable structures and compositions in a high throughput manner. The combination of these remarkable features with proper materials and fabrication methods has enabled high efficiency, direct encapsulation of actives in microparticles whose features and functionalities can be well controlled. These microparticles have great potential in a wide range of bio-related applications including drug delivery, cell-laden matrices, biosensors and even as artificial cells. In this review, we briefly summarize the materials, fabrication methods, and microparticle structures produced with droplet microfluidics. We also provide a comprehensive overview of their recent uses in biomedical applications. Finally, we discuss the existing challenges and perspectives to promote the future development of these engineered microparticles.

Biopolymer Microparticles Prepared by Microfluidics for Biomedical Applications

“…In a typical microfluidic droplet generator, the uniform emulsion droplets are generated through the periodic breakup of the dispersed phase into the continuous phase under the delicate balance among inertial force, viscous force, and interfacial tension . The effect of buoyancy on droplet formation is negligible compared to interfacial and viscous forces because of small channel sizes, flow rates, and droplet volume . The process of droplet generation is determined by two dimensionless numbers, capillary number ( Ca ) and Weber number ( We ), which are directly related to the channel geometries and flow conditions .…”

“…The process of droplet generation is determined by two dimensionless numbers, capillary number ( Ca ) and Weber number ( We ), which are directly related to the channel geometries and flow conditions . The Ca describes the relative effect of viscous shear force and surface tension force, whereas We represents a balance between inertial force and surface tension force as described by the following equations where η c and u c are the viscosity and flow velocity of continuous phase, ρ d and u d are the density and flow velocity of dispersed phase, d tip is the inner diameter of the orifice of tapered injection tip and γ is the interfacial tension between the two fluids . These numbers influence the mechanism of droplet formation by determining transition between the dripping and jetting modes ( Figure A).…”

Microfluidic Generation of Nanomaterials for Biomedical Applications

“…b) Schematic illustration of segmented flow relied on various channel geometries, including T‐junction, coflow, and flow focusing. Reproduced with permission . Copyright 2018, Royal Society of Chemistry.…”

“…Alongside the continuous flow, segmented flow microfluidic system was also presented to synthesize NPs. Various geometries of microfluidic devices (e.g., T‐junction, co‐flow, and flow‐focusing, as shown in Figure b) were designed to generate segmented flows, which include a liquid–liquid interfacial layer for droplets and a gas–liquid interfacial layer for bubbles (Figure c) . In a liquid–liquid segmented flow, the droplets breakup is resulted from the instability of dispersed phase, and presented as water‐in‐oil or oil‐in‐water emulsions.…”

“…Up to now, a number of reviews about microfluidic fabrication of materials have been reported from different aspects, which mainly refer to certain microfluidic technologies (e.g., droplet microfluidics) or specific forms of materials (e.g., microparticles) . However, a comprehensive review that puts the attention on microfluidic fabrication of NMs and their biomedical applications is unavailable.…”