Selective droplet splitting using single layer microfluidic valves

Abstract

Droplet microfluidics, with its small scale isolated samples, offers huge potential in the further miniaturisation of high throughput screening. The challenge is to deliver multiple samples in a manner such that reactions can be performed in numerous permutations. The present study investigates the use of single layer valves to subdivide individual droplets selectively. This partitioning of large droplets, allows the main sample volume to navigate around the chip, with smaller daughter droplets being removed at desired locations. As such, the mother droplet is no longer an isolated sample akin to an onchip test tube, but rather a mobile sample delivery system akin to an on-chip pipette. The partitioning takes place at the entrance to a bypass loop of the main channel. Under normal operating conditions the droplet passes the entrance intact, however, when a valve located at the entrance to the bypass loop is actuated the geometry changes causes the droplet to split. We analyse this transition in behaviour for a range of oil and water inlet, and valve actuation pressures, showing that the valve can be actuated such that the next droplet to pass the bypass loop will be split, but subsequent droplets will not be.

Droplets generation under different flow rates in T‐junction microchannel with a neck

“…Since the significant influence of the geometry on the droplet size, numerous kinds of modified channels based on the normal Tjunction devices are designed. [26][27][28][29][30][31][32][33][34][35] In addition, droplets generations were investigated to get better control of micro-droplets and understand the droplet behaviors in different conditions. Angles between the entrance channels, which was normally set to a right angle, were reported to influence the process of the droplet/bubble breakup.…”

“…Angles between the entrance channels, which was normally set to a right angle, were reported to influence the process of the droplet/bubble breakup. 29,30 The width of the main channel at the junction were varied by adding a protrusion, [26][27][28] a movable membrane/wall, [31][32][33] and additional gas phase, 34,35 to generate droplets of controllable sizes, such as small, uniform, on-demand and with-feedback droplets. The modifications make droplets of specified dimensions, but the scaling law in the normal T-junction can only provide partial adaptability.…”

“…Since the significant influence of the geometry on the droplet size, numerous kinds of modified channels based on the normal T‐junction devices are designed 26‐35 . In addition, droplets generations were investigated to get better control of micro‐droplets and understand the droplet behaviors in different conditions.…”

Droplet‐based microreactor for the production of micro/nano‐materials

“…Therefore, we describe two kinds of the most widely used microfluidic devices, including lithographically fabricated poly(dimethylsiloxane) (PDMS) devices and glass capillary devices for generating various kinds of emulsion droplets. Then, varieties of manipulation methods of droplets are also introduced, such as coalescence , split , and pico‐injection .…”

Thermally-actuated microfluidic membrane valve for point-of-care applications

“…They can be used for switching or adjusting flows between chemicals in a Y-junction geometry 3,4 , for mixing chemicals 5,6 , and for peristaltic pumping 7 . They are also widely used in droplet microfluidics 8 to generate droplets from different chemicals 9 , to alter droplet size and frequency 10 , to split 11 , sort 12 , and to merge droplets 13 .…”