题目：Electrowetting: Theory, Applications, and Hydrodynamics
报告人： Kwan Hyoung Kang
Department of Mechanical Engineering, Pohang University of Science and Technology,
San 31, Hyoja-dong, Pohang 790-784, South Korea
Phone: +82-54-279-2187, Fax: +82-54-279-3199, E-mail: khkang@postech.ac.kr

主持人：熊春阳 副教授
时间：11月5日（周三）下午4:00
地点：湍流与复杂系统国家重点实验室会议室

报告内容摘要：
The electrical control of wettability, which is called the electrowetting, is a versatile tool for handling of micro- and nano-liter drops. The electrowetting can be used as a very fast and efficient means to handle nearly any kind of drops with a relatively low electrical potential and power consumption. In the first part of the talk, I will present the hydrodynamic flows generated inside a droplet in electrowetting when an ac voltage is applied. In order to find out the characteristics and origin of the flows, we investigated the flow pattern for a sessile droplet for various conditions. A shape oscillation of a droplet was observed in the low-frequency range by a high-speed camera. The shape oscillation is responsible for the low-frequency flow. The flow at high frequency is caused by some electrohydrodynamic effect. In the second part of the talk, an experimental and theoretical work will be presented concerning the shape oscillation of sessile droplet. A set of shape mode equations is derived to describe unsteady motions of a sessile drop actuated by electrowetting. A unified boundary condition is obtained, which is valid at the three-phase contact line as well as the drop surface, by combining the equation for dynamic contact angle and the normal stress condition. The equilibrium contact angle of electrowetting predicted by present method shows a good agreement with those of Lippmann-Young equation and our experiments. The present theoretical model is also validated by predicting the spreading process of a droplet for step input voltages. It shows a qualitative agreement with experimental results in temporal evolution of drop shape. Finally, I will present a novel method to actuate oscillation of a sessile bubble or oil drop in a fluid to produce steady streaming within the fluid. This method is based on time-periodic control of the wettability of the bubble or drop by electrowetting. Jet velocity is proportional to oscillation amplitude and is greatest at natural oscillation frequencies. Analytical and numerical analyses indicate that the jet is produced by steady streaming in the Stokes layer.

欢迎广大老师和学生参加！

联系人：熊春阳，010- 62757940
 
KWAN HYOUNG KANG, Ph.D.
Assistant Professor
Department of Mechanical Engineering
Pohang University of Science and Technology (POSTECH)
San 31, Hyoja-dong, Pohang 790-784, South Korea
Phone: +82-54-279-2187, Fax: +82-54-279-5899
Mobile: +82-10-2680-2187
E-mail: khkang@postech.ac.kr
Homepage: http://mf.postech.ac.kr

BRIEF BIO
Kwan Hyoung Kang is an Assistant Professor of Department of Mechanical Engineering at Pohang University of Science and Technology (POSTECH). He works in the microfluidics field with a particular interest in electrical control of microscale fluids and particles including electrowetting, dielectrophoresis, electrokinetics, and electrohydrodynamics. He developed an electromechanical theory of electrowetting and found out the origin of electrowetting phenomenon. He found hydrodynamic flows in ac electrowetting including a synthetic jet produced by an oscillating sessile droplet. He discovered an electrohydrodynamic flow produced by nonuniform electric fields in dielectric liquids. His laboratory has been assigned as one of the National Research Laboratory (NRL) by the Korean government with the title of “Electro-Microfluidics Lab” since year 2007. The project is entitled “Development of an electromechanics-based multi-functional microfluidic platform for handling of microscale fluids and particles.” Ongoing project includes investigations on the switching speeds of electrowetting-based switches and electrophoresis-based electric papers. Prof. Kang received his PhD, MS, and BS in Mechanical Engineering from the POSTECH in 1996, 1993, and 1991, respectively.

EDUCATION
? Ph.D. Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH) in South Korea, (1993. 3 ~ 1996. 8).
? M.S. Department of Mechanical Engineering, POSTECH (1991. 3 ~ 1993. 2).
? B.S. Department of Mechanical Engineering, POSTECH (1987. 3 ~ 1991. 2).

EMPLOYMENT
? Assistant Professor (July 1, 2005~), Department of Mechanical Engineering, POSTECH
? Postdoctorial Fellow (2004.5~Present), Department of Mechanical and Industrial Engineering, University of Toronto (Laboratory for Microfluidic Transport Phenomena)
? Research Assistant Professor/Postdoctorial Fellow (2001.8~2004.5), Department of Mechanical and Industrial Engineering, POSTECH
? Senior Researcher (1999.3 ~ 2000. 8), Samsung Ship Model Basin (SSMB), Samsung Heavy Industries (SHI)
? Postdoctorial Fellow (1998.9~1999.2), Korean Institute of Machinery and Materials (KIMM), Korean Research Institute of Ship and Ocean Engineering (KRISO)
? Researcher (Postdoctorial Fellow) (1996.9~1998.7), Advanced Fluids Engineering Research Center, POSTECH

HONOR, ACADEMIC AWARDS, AND SCHOLARSHIPS
? Presidential Researcher [Principal Investigator of the National Research Laboratory (NRL, Hydroacoustic Research Laboratory)]
? Bronze Medal, Research Excellence Awards of Samsung Heavy Industries (2001). “Project Title: Development of Hydrophone Array System for Underwater Noise Measurement”
? Excellent Paper Presentation Award: The 5th KSME-JSME Fluids Engineering Conference, Nagoya, Japan, November 2002.
? Postdoctorial Scholarships from Korean Science and Engineering Foundation Post Doc. (1998.9~1999.2).

MEMBERSHIPS
? Member, American Physical Society
? Member, Korean Society of Mechanical Engineers (KSME).
? Member, Visualization Society of Korean.

INVITED TALKS
? Hydrodynamic Flows in Electrowetting, The 6th Electrowetting Workshop, UCLA, Los Angeles, 2008.
? Electrowetting: Fundamental Theory and Applications, Samsung Electro-Mechanics, Korea, March, 11, 2004.
? Fluid Mechanics in Microscale and Its Electromagnetic Controls, School of Mechanical Engineering, Pusan National University, Korea, Jan. 14, 2004.
? Fluid Mechanics in Microscale and Its Electromagnetic Controls, School of Mechanical and Aerospace Engineering, Seoul National University, Korea, Nov. 15, 2003.
? Fluid Mechanics in Microscale and Its Electromagnetic Controls, Department of Mechanical Engineering, Chung-Ang University, Korea, Dec. 15, 2003.
? Electrowetting: Microfluidic Applications and Electromechanical Theory, Autumn’s Meeting of Fluids Engineering Division of KSME, Korea University, Seoul, Dec. 2003.
? Electrowetting: Microfluidic Applications and Electromechanical Theory, Department of Chemical Engineering, POSTECH, Sep. 2003.
? Measurement of Hydroacoustic Signiture in a Cavitation Tunnel, Department of Mechanical Engineering, POSTECH, Mar. 2001.
? Measurement of Radiation Noise of Underwater Vehicles, Agency for Defense Development (ADD) of Korea, May 2000.
? Prediction and Control of Cavitation Noise, KRISO (KIMM), May 1998.

INTERNATIONAL JOURNAL PAPERS
[J25] Sung Hee Ko and Kwan Hyoung Kang, “Jet flow produced by electrowetting-driven bubble oscillations in aqueous solution,” Submitted.
[J24] Sung Hee Ko, Seung Jun Lee, Jun Kwon Park, and Kwan Hyoung Kang, “Inherent bistability of electrowetting,” Submitted.
[J23] Jung Min Oh, Sung Hee Ko, and Kwan Hyoung Kang (2008) “Shape Oscillation of a Drop in ac Electrowetting,” Langmuir, 24(15), 8379-8386.
[J22] Jinseok Hong, Sung Hee Ko, Kwan Hyoung Kang, and In Seok Kang (2008) “A numerical investigation on AC electrowetting of a droplet,” Microfluidics and Nanofluidics, 5(2), 263-271.
[J21] Sung Hee Ko, Horim Lee, and Kwan Hyoung Kang (2008) “Hydrodynamic flows in electrowetting,” Langmuir, 24(3), 1094-1101.
[J20] J. M. Oh and K. H. Kang (2007) “Conditions for similitude and the effect of finite Debye length in electroosmotic flows,” J. Colloid Interface Sci. 310, 607-616.
[J19] S. J. Kim, K. H. Kang, I. S. Kang, and B. J. Yoon (2006) “Control of particle-deposition pattern in a sessile droplet by using the radial electroosmotic flow,” Analytical Chemistry, 78(14), 5192- 5197.
[J18] K. H. Kang, J. Park, I. S. Kang, and K. Y. Huh (2006) “Mechanism of the electrohydrodynamic instability of two-layered miscible fluids in microchannels,” Int. J. Heat and Mass Trans.  49, 4577-4583.
[J17] K. H. Kang, X. Xuan, Y. Kang, and D. Li (2006) “Effects of DC-dielectrophoretic force on particle trajectories in microchannels,” J. Appl. Phys. 99(6), 064702.
[J16] K. H. Kang, Y. Kang, X. Xuan, and D. Li (2006) “Continuous separation of microparticles by size with DC-dielectrophoresis,” Electrophoresis. 27 (3): 694-702
[J15] K. H. Kang and D. Li (2006) “Dielectric force and relative motion between two spherical particles in electrophoresis,” Langmuir (American Chemical Society, Journal of Interface and Colloid), 22(4), 1602-1608.
[J14] K. H. Kang and D. Li “Force acting on a dielectric particle in a concentration gradient by ionic concentration polarization under an externally applied DC electric field,” J. Colloid Interface Sci. 286, 792-806.
[J13] K. H. Kang, S. J. Lee, C. M. Lee, and I. S. Kang (2003) “Quantitative visualization of flow inside a two-component evaporating droplet,” Measurement Science & Technology 15(6), 1104 - 1112.
[J12] K. H. Kang and I. S. Kang (2003) “Theoretical investigation on the liquid junction potential in a slit-like microchannel,” J. Electroanalytical Chemistry 566(2), 331-340.
[J11] C. M. Lee, D. G. Han, K. H. Kang and S. J. Lee (2004) “Investigation of effectiveness of tandem oil fences under currents,” J. Marine Science and Technology 8, 117-125.
[J10] K. H. Kang and I. S. Kang (2003) “Validity of the Derjaguin approximation in electrostatic effect on the Frumkin—Derjaguin approach,” Langmuir (American Chemical Society, Journal of Interface and Colloid) 19(23), 9962-9967.
[J9]  K. H. Kang, I. S. Kang, C. M. Lee (2003) “Electrostatic contribution to line tension in a wedge-shaped contact region,” Langmuir, 19(22), 9334-9342.
[J8]  K. H. Kang, I. S. Kang, C. M. Lee (2003) “Geometry dependence of wetting tension on charge-modified surfaces,” Langmuir, 19(17), 6881-6887.
[J7]  K. H. Kang, I. S. Kang, C. M. Lee (2003) “Wetting tension due to Coulombic interaction in charge-related wetting phenomena,” Langmuir, vol. 19(8), 5407-5412.
[J6]  K. H. Kang (2002) “How electrostatic fields change contact angle in electrowetting,” Langmuir, vol. 18(26), 10318–10322.
[J5]  K. H. Kang, I. S. Kang, and C. M. Lee (2002) “Effects of uniform magnetic field on a growing or collapsing bubble in a weakly viscous conducting fluid,” Physics of Fluids, vol. 14(1), 29-40.
[J4]  C, M. Lee, and K. H. Kang (1998) “Prediction of oil boom performance in currents and waves,” Spill Science and Technology Bulletin, vol. 4, pp. 257-266.
[J3]  C. M. Lee, K. H. Kang, and N. S. Cho (1998) "Trapping of leaked oil with tandem oil-fences with Lagrangian analysis of oil droplet motion," Trans. of the ASME. J. Offshore Mech. and Arctic Eng., vol. 120, pp. 50-55.
[J2]  K. H. Kang and C. M. Lee (1996) "Prediction of drift in a free surface," Ocean Engineering, vol. 23, pp. 243~255.
[J1]  K. H. Kang and C. M. Lee (1995) "Steady streaming of viscous surface layer in waves," J. Marine Science and Technology, vol. 1, pp. 3~12.

DOMESTIC JOURNAL PAPERS
[D5] S. K. Chung, K. H. Kang, C. M. Lee, and I. S. Kang (2003) “Analysis of effect of line tension and electrical double layers on electrowetting phenomena” KSME J. B, 27(7), 956–962. (In Korean).
[D4] J. -W. Ahn, K. H. Kang, I. -H. Song, and K. –Y. Kim (2000) "Measurement of cavitation noise of a hydrofoil and prediction of cavity bubble behavior," J. of the Society of Naval Architects of Korea, vol. 37(4), 40-47. (In Korean).
[D3] K. H. Kang and C. M. Lee (1999) "Behavior of oil-water interface between tandem fences," J. Korean Soc. for Marine Environmental Engineering vol. 2, pp. 70-77.
[D2] C. M. Lee and K. H. Kang (1998) "Analysis of containment capability of oil fence in currents and waves,” J. Korean Soc. for Marine Environmental Engineering, vol. 1, pp. 29-38. (In Korean).
[D1] K. H. Kang and C. M. Lee (1996) "Development of an efficient calculation method of pressure acting on a bluff body and deformation of flexible oil fences in currents,” J. of the Society of Naval Architects of Korea, vol. 33, pp. 22-31. (In Korean).