Generation of Monodisperse Particles by Using Microfluidics: Control over Size, Shape, and Composition

Abstract

Herein we describe a versatile new strategy for producing monodisperse solid particles with sizes from 20 to 1000 mm. The method involves the formation of monodisperse liquid droplets by using a microfluidic device and shaping the droplets in a microchannel and then solidifying these drops in situ either by polymerizing a liquid monomer or by lowering the temperature of a liquid that sets thermally. This method has the following features: 1) It produces particles with an exceptionally narrow range of sizes.[1] 2) A new level of control over the shapes of the particles is offered.3) The mechanism for droplet formation allows the use of a wide variety of materials including gels, metals, polymers, and polymers doped with functional additives. 4) The procedure can be scaled up to produce large numbers of particles.

Fabrication, Assembly, and Application of Patchy Particles

“…Selective modification of a segment of a particle surface is directly feasible in the case of the PVD technique because of the inherent shadow effect. In addition to the conventional surface modification techniques, [62,63] more recently capillary flow techniques [13,15,[64][65][66][67] and colloidal assembly [68,69] methods have been explored for the fabrication of patchy particles and therefore will be included here.…”

“…The next two techniques, glancing-angle vapor deposition (Figure 5d) [8,71] and nanoparticle lithography (Figure 5e), [18,19] involve vapor deposition onto close-packed planar particle assemblies. The last technique involves the use of liquid streams in capillaries for fabrication of bi-, tri-and multi-phasic particles from the Lahann, [13,15] Kumacheva [64] and Whitesides [67] groups (Figure 5f). …”

Basic Technologies for Droplet Microfluidics

“…Aspherical particles could also be fabricated by taking advantage of geometric confinement of the microdroplets by the microchannels. Figure 10b shows aspherical particles fabricated by Xu et al [111]. A diskshaped particle could be formed, for instance, by forming and solidifying droplets in a shallow microchannel which will squash the microdroplet into a disk shape upon formation.…”

Microfluidic formulation of pectin microbeads for encapsulation and controlled release of nanoparticles

“…Since the first demonstration of formation of monodisperse droplets in microchannels, 3 a range of techniques have been proposed for generation of simple [3][4][5] and multiple 6 droplets with an extensive control over the distribution of volumes. The ability to form monodisperse segments of liquids can be successfully utilized to formulate monodisperse polymeric particles 7 of various-and easy to control-morphologies 8,9 and capsules. 10 Extensions of these techniques are used to encapsulate biomaterials, 11 prepare microbubble contrast agents for ultrasound radiography, 12 carriers of active substances for targeted drug delivery, 13 and for control of the temporal profile of their release.…”

“…Several methods of gelation have been implanted both on-chip and off-chip to gel the droplets. These methods include chemical ͑commonly radical polymerization 22 ͒ or physical ͑thermal setting 8,23 or ionic cross-linking 24,25 ͒ processes.…”