Abstract
This paper presents a microfluidic system for the active and precise control of microdroplet division in a micro device. Using two horizontal pneumatic valves formed at downstream of bifurcating microchannel, flow resistances of downstream channels were variably controlled. With the resistance control, volumetric ratio of downstream flows was changed and water-in-oil microdroplets were divided into two daughter droplets of different volume corresponding to the ratio. The microfluidic channels and pneumatic valves were fabricated by single-step soft lithography process of PDMS (polydimethylsiloxane) using SU-8 mold. A wide range control of the daughter droplets’ volume ratio was achieved by the simple channel structure. Volumetric ratio between large and small daughter droplets are ranged from 1 to 70, and the smallest droplet volume of 14 pL was obtained. The proposed microfluidic device is applicable for precise and high throughput droplet based digital synthesis.
Highlights
In recent years, microdroplet technologies have been applied to wide research fields as effective methods to handle small samples [1]
To control flow rate in microchannels, we developed horizontal pneumatic valves with a flexible material PDMS [20]
The microdroplet division device consists of droplet generation part, division part and observation part
Summary
Microdroplet technologies have been applied to wide research fields as effective methods to handle small samples [1]. Quantitative volume control, protection and transportation of the small samples are realized in a miniaturized platform. Chemical reactions and biological encapsulations are those representative examples [2,3,4,5,6,7,8]. In use of the technologies, volume control of the droplets is an important issue to maximize the microdroplets’ advantages. In order to achieve volume controlled droplet generation, design optimization of channel structure is required [9,10,11]. An automated flow rate change of immiscible fluids is useful to control the droplet volume [12]. Electrical and chemical methods are helpful to control the droplets’
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