Figure 2. Simulation of droplet separation by EWOD

Non-Linear Electrohydrodynamics in Microfluidic Devices

미세 유체 장치의 비선형 전기 유체 역학

by Jun ZengHewlett-Packard Laboratories, Hewlett-Packard Company, 1501 Page Mill Road, Palo Alto, CA 94304, USAInt. J. Mol. Sci.201112(3), 1633-1649; https://doi.org/10.3390/ijms12031633Received: 24 January 2011 / Revised: 10 February 2011 / Accepted: 24 February 2011 / Published: 3 March 2011

Abstract

Since the inception of microfluidics, the electric force has been exploited as one of the leading mechanisms for driving and controlling the movement of the operating fluid and the charged suspensions. Electric force has an intrinsic advantage in miniaturized devices. Because the electrodes are placed over a small distance, from sub-millimeter to a few microns, a very high electric field is easy to obtain. The electric force can be highly localized as its strength rapidly decays away from the peak. This makes the electric force an ideal candidate for precise spatial control. The geometry and placement of the electrodes can be used to design electric fields of varying distributions, which can be readily realized by Micro-Electro-Mechanical Systems (MEMS) fabrication methods. In this paper, we examine several electrically driven liquid handling operations. The emphasis is given to non-linear electrohydrodynamic effects. We discuss the theoretical treatment and related numerical methods. Modeling and simulations are used to unveil the associated electrohydrodynamic phenomena. The modeling based investigation is interwoven with examples of microfluidic devices to illustrate the applications. 

Keywords: dielectrophoresiselectrohydrodynamicselectrowettinglab-on-a-chipmicrofluidicsmodelingnumerical simulationreflective display

요약

미세 유체학이 시작된 이래로 전기력은 작동 유체와 충전 된 서스펜션의 움직임을 제어하고 제어하는 ​​주요 메커니즘 중 하나로 활용되어 왔습니다. 전기력은 소형 장치에서 본질적인 이점이 있습니다. 전극이 밀리미터 미만에서 수 미크론까지 작은 거리에 배치되기 때문에 매우 높은 전기장을 쉽게 얻을 수 있습니다. 

전기력은 강도가 피크에서 멀어지면서 빠르게 감소하기 때문에 고도로 국부화 될 수 있습니다. 이것은 전기력을 정밀한 공간 제어를 위한 이상적인 후보로 만듭니다.

전극의 기하학적 구조와 배치는 다양한 분포의 전기장을 설계하는 데 사용될 수 있으며, 이는 MEMS (Micro-Electro-Mechanical Systems) 제조 방법으로 쉽게 실현할 수 있습니다. 

이 논문에서 우리는 몇 가지 전기 구동 액체 처리 작업을 검토합니다. 비선형 전기 유체 역학적 효과에 중점을 둡니다. 이론적 처리 및 관련 수치 방법에 대해 논의합니다. 모델링과 시뮬레이션은 관련된 전기 유체 역학 현상을 밝히는 데 사용됩니다. 모델링 기반 조사는 응용 분야를 설명하기 위해 미세 유체 장치의 예와 결합됩니다. 

키워드 : 유전 영동 ; 전기 유체 역학 ; 전기 습윤 ; 랩 온어 칩 ; 미세 유체 ; 모델링 ; 수치 시뮬레이션 ; 반사 디스플레이

Droplet processing array Droplet based BioFlip
igure 1. Example of droplet-based digital microfluidics architecture. Above is an elevation view showing the layered structure of the chip. Below is a diagram illustrating the system (Adapted from [4]).
Figure 2. Simulation of droplet separation by EWOD
Figure 2. Simulation of droplet separation by EWOD. The top two figures illustrate the device configuration. Electric voltages are applied to all four electrodes embedded in the insulating material. The bottom left figure shows transient simulation solution. It illustrates the process of separating one droplet into two via EWOD. The bottom right figure shows the electric potential distribution inside the device. The color indicates the electric potential; the iso-potential surfaces are also drawn. The image shows the electric field is absent within the droplet body indicating the droplet is either conductive or highly polarizable.
Figure 4. Transient sequence of the Taylor cone formation
Figure 4. Transient sequence of the Taylor cone formation: simulation and experiment comparison. Experimental images are shown in the top row. Simulation results are shown in the bottom row. Their correspondence is indicated by the vertical alignment (Adapted from [4]).
Figure 6. Simulation of charge screening effect using a parallel-plate cell
Figure 6. Simulation of charge screening effect using a parallel-plate cell. Top-left image shows the electric current as function of time and driving voltage, top-right image shows the evolution of the species concentration as function of time and space, the bottom image shows the electric current readout after switching the applied voltage.
Figure 7. Transient simulation of electrohydrodynamic instability and the development of the cellular convective flow pattern.
Figure 7. Transient simulation of electrohydrodynamic instability and the development of the cellular convective flow pattern.
Figure 3. Simulation of dielectrophoresis driven axon migration
Figure 3. Simulation of dielectrophoresis driven axon migration. The set of small images on the left shows a transient simulation of single axon migration under an electric field generated by a pin electrode. The image on the right is a snapshot of a simulation where two axons are fused by dielectrophoresis using a pin electrode. Axons are outlined in white. Also shown are the iso-potential curves.

References

  1. Muller, RS. MEMS: Quo vadis in century XXI. Microelectron. Eng 200053(1–4), 47–54. [Google Scholar]
  2. Reyes, DR; Iossifidis, D; Auroux, PA; Manz, A. Micro total analysis systems. 1. Introduction, theory, and technology. Anal.Chem 200274, 2623–2636. [Google Scholar]
  3. Levy, U; Shamai, R. Tunable optofluidic devices. Microfluid. Nanofluid 20084, 97–105. [Google Scholar]
  4. Zeng, J; Korsmeyer, FT. Principles of droplet electrohydrodynamics for lab-on-a-chip. Lab Chip 20044, 265–277. [Google Scholar]
  5. Fair, RB. Digital microfluidics: Is a true lab-on-a-chip possible? Microfluid. Nanofluid 20073, 245–281. [Google Scholar]
  6. Pollack, MG; Fair, RB; Shenderov, AD. Electrowetting-based actuation of liquid droplets for microfluidic applications. Appl. Phys. Lett 200077(11), 1725–1726. [Google Scholar]
  7. Peykov, V; Quinn, A; Ralston, J. Electrowetting: A model for contact-angle saturation. Colloid Polym. Sci 2000278, 789–793. [Google Scholar]
  8. Verheijen, HJJ; Prins, MWJ. Reversible electrowetting and trapping of charge: Model and experiments. Langmuir 199915, 6616–6620. [Google Scholar]
  9. Mugele, F; Baret, J. Electrowetting: From basics to applications. J. Phys. Condens. Matter 200517, R705–R774. [Google Scholar]
  10. Quilliet, C; Berge, B. Electrowetting: A recent outbreak. Curr. Opin. Colloid Interface Sci 20016, 34–39. [Google Scholar]
  11. Probstein, RF. Physicochemical Hydrodynamics; Wiley: New York, NY, USA, 1994. [Google Scholar]
  12. Koo, J; Kleinstreuer, C. Liquid flow in microchannels: Experimental observations and computational analyses of microfluidics effects. J. Micromech. Microeng 200313, 568–579. [Google Scholar]
  13. Hu, G; Li, D. Multiscale phenomena in microfluidics and nanofluidics. Chem. Eng. Sci 200762, 3443–3454. [Google Scholar]
  14. Haus, HA; Melcher, JR. Electromagnetic Fields and Energy; Prentice-Hall: Englewood Cliffs, NJ, USA, 1989. [Google Scholar]
  15. Leal, LG. Laminar Flow and Convective Transport Processes: Scaling Principles and Asymptotic Analysis; Butterworth-Heinemann: Oxford, UK, 1992. [Google Scholar]
  16. Collins, RT; Harris, MT; Basaran, OA. Breakup of electrified jets. J. Fluid Mech 2007588, 75–129. [Google Scholar]
  17. Sista, R; Hua, Z; Thwar, P; Sudarsan, A; Srinivasan, V; Eckhardt, A; Pollack, M; Pamula, V. Development of a digital microfluidic platform for point of care testing. Lab Chip 20088, 2091–2104. [Google Scholar]
  18. Zeng, J. Modeling and simulation of electrified droplets and its application to computer-aided design of digital microfluidics. IEEE Trans. Comput. Aid. Des. Integr. Circ. Syst 200625(2), 224–233. [Google Scholar]
  19. Walker, SW; Bonito, A; Nochetto, RH. Mixed finite element method for electrowetting on dielectric with contact line pinning. Interface. Free Bound 201012, 85–119. [Google Scholar]
  20. Eck, C; Fontelos, M; Grün, G; Klingbeil, F; Vantzos, O. On a phase-field model for electrowetting. Interface. Free Bound 200911, 259–290. [Google Scholar]
  21. Gascoyne, PRC; Vykoukal, JV. Dielectrophoresis-based sample handling in general-purpose programmable diagnostic instruments. Proc. IEEE 200492(1), 22–42. [Google Scholar]
  22. Jones, TB; Gunji, M; Washizu, M. Dielectrophoretic liquid actuation and nanodroplet formation. J. Appl. Phys 200189(3), 1441–1448. [Google Scholar]
  23. Sretavan, D; Chang, W; Keller, C; Kliot, M. Microscale surgery on single axons. Neurosurgery 200557(4), 635–646. [Google Scholar]
  24. Pohl, HA; Crane, JS. Dielectrophoresis of cells. Biophys. J 197111, 711–727. [Google Scholar]
  25. Melcher, JR; Taylor, GI. Electrohydrodynamics: A review of the role of interfacial shear stresses. Annu. Rev. Fluid Mech 19691, 111–146. [Google Scholar]
  26. Saville, DA. Electrohydrodynamics: The taylor-melcher leaky-dielectric model. Annu. Rev. Fluid Mech 199729, 27–64. [Google Scholar]
  27. Schultz, GA; Corso, TN; Prosser, SJ; Zhang, S. A fully integrated monolithic microchip electrospray device for mass spectrometry. Anal. Chem 200072(17), 4058–4063. [Google Scholar]
  28. Killeen, K; Yin, H; Udiavar, S; Brennen, R; Juanitas, M; Poon, E; Sobek, D; van de Goor, T. Chip-MS: A polymeric microfluidic device with integrated mass-spectrometer interface. Micro Total Anal. Syst 2001, 331–332. [Google Scholar]
  29. Dukhin, SS. Electrokinetic phenomena of the second kind and their applications. Adv. Colloid Interface Sci 199135, 173–196. [Google Scholar]
  30. Wang, Y-C; Stevens, AL; Han, J. Million-fold preconcentration of proteins and peptides by nanofluidic filter. Anal. Chem 200577(14), 4293–4299. [Google Scholar]
  31. Kim, SJ; Wang, Y-C; Han, J. Nonlinear electrokinetic flow pattern near nanofluidic channel. Micro Total Anal. Syst 20061, 522–524. [Google Scholar]
  32. Comiskey, B; Albert, JD; Yoshizawa, H; Jacobson, J. An electrophoretic ink for all-printed reflective electronic displays. Nature 1998394(6690), 253–255. [Google Scholar]
  33. Beunis, F; Strubbe, F; Neyts, K; Bert, T; De Smet, H; Verschueren, A; Schlangen, L. P-39: Electric field compensation in electrophoretic ink display. In Proceedings of the Twenty-fifth International Display Research Conference—Eurodisplay 2005; Edinburgh, UK, 19–22 2005; pp. 344–345. [Google Scholar]
  34. Strubbe, F; Verschueren, ARM; Schlangen, LJM; Beunis, F; Neyts, K. Generation current of charged micelles in nonaqueous liquids: Measurements and simulations. J. Colloid Interface Sci 2006300, 396–403. [Google Scholar]
  35. Hsu, MF; Dufresne, ER; Weitz, DA. Charge stabilization in nonpolar solvents. Langmuir 200521, 4881–4887. [Google Scholar]
  36. Hayes, RA; Feenstra, BJ. Video-speed electronic paper based on electrowetting. Nature 2003425, 383–385. [Google Scholar]
  37. Chakrabarty, K; Su, F. Digital Microfluidic Biochips: Synthesis, Testing, and Reconfiguration Techniques; CRC Press: Boca Raton, FL, USA, 2006. [Google Scholar]
  38. Chakrabarty, K; Fair, RB; Zeng, J. Design tools for digital microfluidic biochips: Towards functional diversification and more than Moore. IEEE Trans.CAD Integr. Circ. Syst 201029(7), 1001–1017. [Google Scholar]

Lab-on-a-chip – Joule heating and circulation in conducting fluid (전도성 유체의 줄 가열 및 순환)

Joule heating and circulation in conducting fluid (전도성 유체의 줄 가열 및 순환)

  • 줄 가열은 전류가 전도성 유체를 통과 할 때 발생함
    – 유체가 유전체인 경우에 전기장이 있을 경우 분극이 발생하여 유동이 발생
  • 많은 미세 유체의 공정은 마이크로 채널 내부의 유체를 조작하기 위해 외부의 자기력 및 전기력을 필요로 함
    – 유체에 대하여 이러한 외력이 미치는 영향을 이해하는 것이 중요함

FLOW-3D에서의 줄 가열 및 유동 시뮬레이션

  • 시뮬레이션 파라미터
    – 파란색 전극은 +9V, 분홍색 전극은 -9V
    – 전극 위의 유전체 유체 전도
  • 줄 가열은 유체의 온도를 500도로 상승시킴
  • 분극 유체는 전기장 윤곽을 따라 유체의 속도를 유도함