title: Active microdroplet merging by hydrodynamic flow control using a pneumatic actuator-assisted pillar structure.
abstract: This paper describes a microdroplet merging device that can actively control the merging of various droplets under a wide range of flow conditions, using a simple structure. The microdroplets were trapped and merged in a wide chamber divided by pillars, and their behavior was controlled by two horizontal pneumatic microactuators. Hydrodynamic flow control by the actuation was evaluated numerically, and the trapping and merging of droplets were achieved experimentally and controlled via pressure applied to the microactuators. Furthermore, two independently generated droplets were merged under four different modes, ranging from no merging to four-droplet merging, with different ratios and volumes. The pneumatic actuators allowed not only the control of the number of merged droplets, but also a wide range of applied droplet volumes. The device was fabricated simply using a single-layer PDMS (polydimethylsiloxane) structure, and the continuous merging performance operated using only hydrodynamic flow control without any surfactant. Finally, chemical synthesis of a metal complex was performed by the droplet merging method. Crystallization of the complex was visualized in real time, and the synthesis was verified by ultraviolet-visible spectroscopy.
authors: Faculty of Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, Japan. yoon@shoji.comm.waseda.ac.jp.
authors: Dong Hyun
authors: DH
authors: Yoon
authors: Afshan
authors: A
authors: Jamshaid
authors: Junichi
authors: J
authors: Ito
authors: Asahi
authors: A
authors: Nakahara
authors: Daiki
authors: D
authors: Tanaka
authors: Takashiro
authors: T
authors: Akitsu
authors: Tetsushi
authors: T
authors: Sekiguchi
authors: Shuichi
authors: S
authors: Shoji
mesh_terms: D003460:Crystallization; D004129:Dimethylpolysiloxanes; D004867:Equipment Design; D057446:Hydrodynamics; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D010316:Particle Size; D013056:Spectrophotometry, Ultraviolet
chemical_list: D004129:Dimethylpolysiloxanes; C013830:baysilon