WIDE RANGE DYNAMIC VOLUME RATIO AND SIZE CONTROL OF MICRODROPLETS USING ACTIVE DROPLET DIVISION DEVICE J. Ito 1 , D. H. Yoon 1 , T. Sekiguchi 2 , and S. Shoji 1 1 Major in Nanoscience and Nanoengineering, Waseda University, Japan 2 Nanotechnology Research Center, Waseda University, Japan ABSTRACT We designed and fabricated a droplet division device for a wide range dynamic volume ratio and size control of microdroplets. Water-in-oil microdroplets generated at cross junction were separated using active flow resistance control of a Y-shaped droplet division device. Flow resistance of each outlet channel is controlled by two horizontal pneumatic valves formed at the downstream of the bifurcating microchannel. Available volume ratio of daughter microdroplets ranged from 1:1 to 1:145. Size control from about 9 pl to 1 nl was also realized. The generation rate is constant even if the droplet sizes are different in three digits. KEYWORDS: Microfluidic, Droplet, Division, Pneumatic valve INTRODUCTION Microdroplet technologies are effective methods to control small samples [1], and they have been developed in recent years to apply to chemical reaction and encapsulation of a single cell [2]. In order to maximize their advantages, volume and size control of microdroplets is one of the important issues. If two types of volume controlled microdroplets are generated and merged by precise microfluidic control, a series of microdroplets with various concentration ratios can be generated in a microfluidic device. Efficient chemical synthesis of various compounding ratios useful for drug discovery can also be performed by integrating above microfluidic devices. Microdroplet generation at cross junction is a well-known method [3]. However, there is a limit in generation of microdroplets of different volume and size by control of two-phase flow rates. Low generation rate is another disadvantage. Therefore, our group has studied about droplet division devices to obtain wide range volume and size control and high throughput of droplet generation. Using two types of cascade multi-stage separation devices with shifted-pillar structure and asymmetric wall structure, microdroplets of different volume ratio could be generated [4]. However, the range of volume and size of microdroplets was limited in the fixed structure. On the other hand, horizontal pneumatic microvalves which can widely control flow resistance of microchannnels were developed in PDMS (polydimethylsiloxane) microfluidic devices and systems [5]. In this paper, we present a microfluidic device which can control volume and size of microdroplets in a wide range. By integrating bifurcating microchannel with pneumatic valves, a wide range dynamic volume ratio and size control and high throughput generation of microdroplets were achieved. CONCEPT Figure 1 shows the principle of microdroplet division by flow resistance control in the bifurcating microchannel. When microdroplets are divided in a bifurcation point, the volume ratio of two daughter droplets depends on the downstream flow resistance. Since the flow rate of the channel with higher flow resistance is lower than that of the other channel, the size of daughter microdroplets becomes smaller. Therefore, if the flow resistance could be precisely controlled, it is possible to divide microdroplets in any ratios. Figure 1: Controllable microdroplet division in bifurcating microchannel using a change in flow resistance of downstream 978-0-9798064-6-9/µTAS 2013/$20©13CBMS-0001 742 17th International Conference on Miniaturized Systems for Chemistry and Life Sciences 27-31 October 2013, Freiburg, Germany