Effect of local kinematic history on the dynamic self-assembly of droplets in micro-expansion channels

Seungyoung Yang,Sung Won Ahn,Ah Reum Kang,이대웅,Sung Sik Lee,김주민,안경현,Seung Jong Lee 한국유변학회 2011 Korea-Australia rheology journal Vol.23 No.3

Dynamic self-assembly of droplets, regular structure formation of moving deformable objects in a confinement environment is a challenging problem in nonlinear dynamics and engineering patterned structure. In the current work, we investigated how the local kinematic history affects the dynamic self-assembly of picoliter-sized droplets near the expansion regions in microfluidic devices. The local kinematic history was controlled by the shape of the expansion region and characterized using computational fluid dynamics. Size-controlled aqueous droplets in light mineral oil were continuously generated at T-junction microchannel and transported toward the expansion region. The fast dynamics of the droplets was tracked using high-speed video microscopy. We found three types of dynamic droplet arrays: 1D, 2D zigzag, and irregular. The order-disorder transition was associated not only with the droplet size, but also with the controlled local kinematic history, which results in the transient deformation of droplet and droplet-droplet interactions. The present results provide us with insight into the dynamic self-assembly of droplets and could be a useful guide for practical applications of droplet-based microfluidics.

Scalable static droplet array for biochemical assays based on concentration gradients

Lee, Byungjin,Jin, Si Hyung,Noh, Young-Moo,Jeong, Seong-Geun,Jeong, Heon-Ho,Lee, Chang-Soo Elsevier 2018 Sensors and actuators. B, Chemical Vol.273 No.-

<P><B>Abstract</B></P> <P>Many important biological assays demand rapid and low-cost screening systems. In this study, we present a scalable static droplet array (SDA) that can generate a high-resolution concentration gradient. The system consists of discrete sample dispensing channels, array units, and microvalves for droplet generation and droplet storage. We utilize negative pressure on a suction valve located below array chambers to enhance the capacity of droplet filling. The size of the droplets is controlled by valve actuation time, and array chambers can contain up to 32 droplets with a 20-millisecond valve actuation time. We present various profiles of concentration gradients generated by the combined storage of binary concentrations of droplets. As a proof of concept, we performed an enzymatic inhibition assay for validating our system with IC50 and the Hill coefficient using β–galactosidase (β-gal), di(β-<SMALL>D</SMALL>-galactopyranoside) (FDG) and 2-Phenylethyl β-<SMALL>D</SMALL>-thiogalactoside (PETG), and achieved an IC50 value of 2.18 μM and a Hill coefficient of 1.11, which agrees well with results in the literature. We anticipate that this system will serve as a general assay platform that is capable of high-throughput screening for various biological assays and imaging.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study presents a scalable static droplet array (SDA) device that can generate a high-resolution concentration gradient. </LI> <LI> Different profiles of concentration gradients are generated by the combined storage of binary concentrations of droplets. </LI> <LI> The analysis of the IC50 and the Hill coefficient in an enzymatic inhibition assay proves the performance of a scalable SDA. </LI> </UL> </P>

Effect of local kinematic history on the dynamic self-assembly of droplets in micro-expansion channels

Yang, Seung-Young,Ahn, Sung-Won,Kang, Ah-Reum,Lee, Dae-Woong,Lee, Sung-Sik,Kim, Ju-Min,Ahn, Kyung-Hyun,Lee, Seung-Jong 한국유변학회 2011 Korea-Australia rheology journal Vol.23 No.3

Dynamic self-assembly of droplets, regular structure formation of moving deformable objects in a confinement environment is a challenging problem in nonlinear dynamics and engineering patterned structure. In the current work, we investigated how the local kinematic history affects the dynamic self-assembly of picoliter-sized droplets near the expansion regions in microfluidic devices. The local kinematic history was controlled by the shape of the expansion region and characterized using computational fluid dynamics. Sizecontrolled aqueous droplets in light mineral oil were continuously generated at T-junction microchannel and transported toward the expansion region. The fast dynamics of the droplets was tracked using high-speed video microscopy. We found three types of dynamic droplet arrays: 1D, 2D zigzag, and irregular. The orderdisorder transition was associated not only with the droplet size, but also with the controlled local kinematic history, which results in the transient deformation of droplet and droplet-droplet interactions. The present results provide us with insight into the dynamic self-assembly of droplets and could be a useful guide for practical applications of droplet-based microfluidics.

A Study on the Characteristics of Soot Formation and Oxidation in Free Fuel Droplet Array

Lee, Myung-Jun,Kim, Jong-Youl,Yeom, Jeong-Kuk,Ha, Jong-Yul,Chung, Sung-Sik The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.6

In this study, it was attempted to obtain the fundamental data for the formation and oxidation of soot from a diesel engine. Combustion of spray injected into a cylinder is complex phenomenon having physical and chemical processes, and these processes affect each other. There are many factors in the mechanism of the formation and oxidization of soot and it is necessary to observe spray combustion microscopically. In order to observe with that view, free fuel droplet array was used as an experimental object and the droplet array was injected into an atmospheric combustion chamber with high temperature. Ambient temperature of the combustion chamber, interdroplet spacing, and droplet diameter were selected as parameters, which affect the formation and oxidation of soot. In this study, it was found that the parameters also affect ignition delay of droplet. The ambient temperature especially affected the ignition delay of droplet as well as the flame temperature after self-ignition. As the interdroplet spacing that means the local equivalence ratio in a combustion chamber was narrow, formation of soot was increased. As diameter of droplet was large, surface area of the droplet was also broad, and hence evaporation of the droplet was more active than that of a droplet with relative small diameter.

이멀션유의 일차원 액적 배열에서 점화특성에 관한 실험적 연구

정인철(Incheol Jeong),이경환(Kyung-Hwan Lee),김재수(Jaesoo Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

The auto-ignition characteristics and combustion behaviors of one-dimensional array of water-in-fuel droplets suspended in a high temperature air chamber have been investigated experimentally with various droplet spacing, number of droplet. The used fuels were pure n-Decane and emulsified n-Decane with varied water contents. All experiments have been performed under the atmospheric conditions. The imaging technique with high-speed camera has been adopted to measure ignition delay, flame life time. It was also applied to observe micro-explosion behaviors. As the droplet array spacing increases, the ignition delay was increased regardless of water contents. However, the life time of droplet array was decreased as the droplet spacing increases.

Numerical analyses of the coupleddynamic behavior of droplets on a vibrating membrane with a microsphere array at a three-phase interface

Dong-Su Park,Kyoung-Su Park 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2

Analyses of the dynamic behavior of droplets are significant for a broad range of industrial applications. However, previous works have primarily studied the dynamic behavior on solid flat plates. Therefore, they could consider both the effect of geometric structure and energy simultaneously. In order to analyze the coupled-dynamic behavior of droplets, SMA membranes with microsphere arrays were used to apply the effects of both geometry and energy to droplet surfaces. The shape of the droplet changed harmonically with time during actuation. In the simulation, 50 and 200 Hz excitations related to the first and second droplet frequencies, respectively were used in order to investigate the coupled-behavior of the droplet. COMSOL Multiphysics TM was used to numerically analyze the dynamic behavior of droplets. The simulation results showed that the dynamic behavior of the water droplet was strongly affected by the natural frequency, and the interface and behavior were determined by both the mode shape and vibrating energy. As the actuation frequency increased, the energy equilibrium changed at the interface and occasionally broke. And then, the contact line on the actuated surface was changed to create new stable state.

Droplet-Based Manufacturing 공정에 의해 제조된 무연 솔더볼의 제조공정 변수 연구

엄호천,조경목,송인혁,한유동 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.1

Uniform droplet of lead-free solder balls was produced by using the Droplet-Based Manufacturing(DBM) process. Compositions of solder were Sn, Sn-3.6 wt.% Ag, and Sn-3.8 wt.%Ag-0.6 wt.% Zn. Effect of parameters such as orifice size, pressure difference, and frequency on the solder ball production was also investigated. Mean size, size distribution, and surface defect of solder balls were analyzed with variations of the parameters. Droplet spacing decreased with increasing frequency and decreasing pressure difference. Thus the size of solder ball decreased with increasing frequency and decreasing pressure difference. Size distribution fell within the narrow range of ±5% from the mean diameter of solder balls. The experimentally measured diameter of the solder balls fabricated by DBM process coincided quite well with the theoretically anticipated value of d_d=A d_o^2/3.

Flame Spread Mechanism of a Blended Fuel Droplet Array at Supercritical Pressure

Iwahashi, Takeshi,Kobayashi, Hideaki,Niioka, Takashi The Korean Society of Combustion 2002 한국연소학회지 Vol.7 No.1

Flame spread experiments of a fuel droplet array were performed using a microgravity environment. N-decane, 1-octadecene, and the blends (50% : 50% vol.) of these fuels were used and the experiments were conducted at pressures up to 5.0 MPa, which are over the critical pressure of these fuels. Observations of the flame spread phenomenon were conducted for OH radical emission images recorded using a high-speed video camera. The flame spread rates were calculated based on the time history of the spreading forehead of the OH emission images. The flame spread rate of the n-decane droplet-array decreased with pressure and had its minimum at a pressure around half of the critical pressure and then increased again with pressure. It had its maximum at a pressure over the critical pressure and then decreased gradually. The pressure dependence of flame spread rate of 1-octadecene were similar to those of n-decan, but the magnitude of the spread rate was much smaller than that of n-decane. The variation of the flame spread for the blended fuel was similar to that of n-decane in the pressure range from atmospheric pressure to near the critical pressure of the blended fuel. When the pressure increased further, it approached to that of 1-octadecene. Numerically estimated gas-liquid equilibrium states proved that almost all the fuel gas which evaporated from the droplet at ordinary pressure consisted of n-decane whereas near and over the critical pressure, the composition of the fuel gas was almost the same as that of the liquid phase, so that the effects of 1-octadecene on the flame spread rate was significant.

A droplet-based biochemical analysis based on scalable microfluidic static droplet array device with chemical concentration gradients

Byungjin LEE,Heon-Ho JEONG,Chang-Soo LEE 한국생물공학회 2018 한국생물공학회 학술대회 Vol.2018 No.4

Droplet routing in high-level synthesis of configurable digital microfluidic biochips based on microelectrode dot array architecture

Zhongkai Chen,Daniel Hsiang-Yung Teng,Gary Chung-Jhih Wang,Shih-Kang Fan 한국바이오칩학회 2011 BioChip Journal Vol.5 No.4

Droplet-based digital microfluidic lab-onchips exploiting electrowetting-on-dielectric (EWOD) have been studied over the last decade. With the recent introduction of new highly scalable, reconfigurable and field-programmable microelectrode dot array (MEDA) architecture, there is a compelling need for a new digital microfluidics synthesizer for the new MEDA architecture. Droplet routing is a critical part of the digital microfluidics synthesizer. This paper presents a routing algorithm and the associated performance analysis results. The algorithm is able to route different sizes of reagent and sample droplets simultaneously and also incorporates other characteristics such as diagonal movements and channel-based movements that are specific to the MEDA architecture.