Straight-through microchannel devices for generating monodisperse emulsion droplets several microns in size

Abstract

The authors recently proposed a promising technique for producing monodisperse emulsions using a straight-through microchannel (MC) device composed of an array of microfabricated oblong holes. This research developed new straight-through MC devices with tens of thousands of oblong channels of several microns in size on a silicon-on-insulator plate, and investigated the emulsification characteristics using the microfabricated straightthrough MC devices. Monodisperse oil-in-water (O/W) and W/O emulsions with average droplet diameters of 4.4-9.8 lm and coefficients of variation of less than 6% were stably produced using surface-treated straight-through MC devices that included uniformly sized oblong channels with equivalent diameters of 1.7-5.4 lm. The droplet size of the resultant emulsions depended greatly on the size of the preceding oblong channels. The emulsification process using the straight-through MC devices developed in this research had very high apparent energy efficiencies of 47-60%, defined as (actual energy input applied to droplet generation/theoretical minimum energy input necessary for making droplets) · 100. Straight-through MC devices with numerous oblong microfluidic channels also have great potential for increasing the productivity of monodisperse fine emulsions.

Porous polymer particles—A comprehensive guide to synthesis, characterization, functionalization and applications

“…Moreover, researchers developed microchannel emulsification for which every hole (channel) for discrete phase droplet formation is custom made. Silicon [115][116][117][118], metal [119][120] and polymer [121][122] based highly uniform microchannels have been used for monodisperse (CV <5%) particle manufacture [123]. The difference between membrane and microchannel emulsification is the fabrication of the emulsification material, which in turn affects the pore size distribution.…”

Production of uniform droplets using membrane, microchannel and microfluidic emulsification devices

“…Asymmetric straight-through MCs have also been used successfully for production of W/O emulsions , polyunsaturated fatty acids (PUFA)-loaded O/W emulsions (Neves et al, 2008) and n-tetradecane emulsions (Vladisavljević et al, , 2011a. The size of droplets produced using asymmetric silicon MCs can range from several microns (Kobayashi et al, 2008b) to several hundred microns .…”

Parallel generation of uniform fine droplets at hundreds of kilohertz in a flow-focusing module

“…MCE chips use microchannel arrays with a terrace to drive the dispersed phase into the gentle continuous phase flow; spontaneous droplet formation thereby depends only on the dispersed phase flow and the geometry of the device. The works of Kobayashi et al [18][19][20] nicely illustrate this technique. Soybean oil droplets of 31-32 lm in diameter and a CV of 9%-10% were produced, in a silicon straightthrough microchannel plate with 211248 channels, at a throughput capacity of 20-30 ml h À1 .…”

“…18 This maximum flow rate of the to-be-dispersed phase fell to 50 ll h À1 , though, when straightthrough microchannels were downsized to form droplets below 10 lm (corresponding to a generation rate of 1.8 Â 10 4 Hz), due to the low percentage of active channels. 19 More recently, Kobayashi et al 20 presented a 60 Â 60-mm MCE chip made of single-crystal silicon, containing 14 microchannel arrays and 1.2 Â 10 4 microchannels, for mass-producing uniform fine droplets of soybean oil; throughput reached 1.5 ml h À1 , with an average droplet diameter of 10 lm. Similarly, van Dijke et al 21 reported on three parallelized designs of the edge-based droplet generation mechanism; formation of 7.5 lm droplets, which occurs spontaneously along a shallow, very wide slit, reached an estimated 250 droplets per 100 lm plateau length, with a CV below 10%.…”