Microfluidic droplet sorting using integrated bilayer micro-valves

Abstract

This paper reports on a microfluidic device capable of sorting microfluidic droplets utilizing conventional bilayer pneumatic micro-valves as sorting controllers. The device consists of two micro-valves placed symmetrically on two sides of a sorting area, each on top of a branching channel at an inclined angle with respect to the main channel. Changes in transmitted light intensity, induced by varying light absorbance by each droplet, are used to divert the droplet from the sorting area into one of the three outlet channels. When no valve is activated, the droplet flows into the outlet channel in the direction of the main channel. When one of the valves is triggered, the flexible membrane of valve will first be deflected. Once the droplet leaves the detection point, the deflected membrane will immediately return to its default flattened position, thereby exerting a drawing pressure on the droplet and deviating it from its original streamline to the outlet on the same side as the valve. This sorting method will be particularly suitable for numerous large-scale integrated microfluidic systems, where pneumatic micro-valves are already used. Only few structural modifications are needed to achieve droplet sorting capabilities in these systems. Due to the mechanical nature of diverting energy applied to droplets, the proposed sorting method may induce only minimal interference to biological species or microorganisms encapsulated inside the droplets that may accompany electrical, optical and magnetic-based techniques. Published by AIP Publishing.

3D high-density microelectrode array with optical stimulation and drug delivery for investigating neural circuit dynamics

“…Also, integrating multiple pumps and tubes into probe shanks for independent drug deliveries requires cumbersome fluidic interfaces. These limitations can be overcome by attaching μLED 62,63 in each shank and applying active valves 64,65 for ondevice fluidic control. In addition, as neurotechnologies continue to advance, our system may still be improved further with a few additional features.…”

Actuation Mechanism of Microvalves: A Review

“…The marking LC stands for liquid channel, P is for pressure, indicating the volume where the pressure for opening or closing is applied, cross-hatch is a PDMS layer, diagonal-hatch glass or thermoplastic layers [74]. Because of the simple structure and low cost, the pneumatic microvalve is applied to many applications including microfluidic circuits design [75], fuel cell systems [78], mix and sort droplets [79,80], rapid hydrodynamic sample injection [81] and so on. What is more, due to the ease of fabrication and robust operation, microfluidic systems have been developed with the multiple pneumatic microvalves to improve throughput and expand applications [73,80], which are shown in Figure 10.…”

“…Because of the simple structure and low cost, the pneumatic microvalve is applied to many applications including microfluidic circuits design [75], fuel cell systems [78], mix and sort droplets [79,80], rapid hydrodynamic sample injection [81] and so on. What is more, due to the ease of fabrication and robust operation, microfluidic systems have been developed with the multiple pneumatic microvalves to improve throughput and expand applications [73,80], which are shown in Figure 10. A microfluidic platform including a pneumatic microvalve could complete electrokinetic sample preconcentration and rapid hydrodynamic sample injection [81].…”

“…Because light absorbance of every type droplet was different, changing intensity of light was applied to transfer the droplet to different outlet channels. The current microfluidic systems only needed some modification of structure for achieving droplet sorting function by this sorting method [80].…”

Selective droplet splitting using single layer microfluidic valves

“…60 These pneumatic valves offer simplicity, ease of fabrication, highpower density, bio-compatibility and versatility, 61,62 and multiple valves can be controlled independently and simultaneously. 63 Their ability to control fluid behaviour has also meant they have been applied to two phase systems; generating 64,65 , sorting 66 , merging 65 and mixing 67,68 has been achieved. In most cases, the deformation of the channel geometry caused by valve operation causes a number of droplets to demonstrate altered behaviour, whether that is droplet size upon generation or toggling between merging and non-merging events.…”