Electrowetting: a versatile tool for drop manipulation, generation, and characterization.

Electrowetting is arguably the most flexible tool to control and vary the wettability of solid surfaces by an external control parameter. In this article we briefly discuss the physical origin of the electrowetting effect and subsequently present a number of approaches for selected novel applications. Specifically, we will discuss the use of EW as a tool to extract materials properties such as interfacial tensions and elastic properties of drops. We will describe some modifications of the EW equation that apply at finite AC voltage for low conductivity fluids when the electric field can partially penetrate into the drops. We will discuss two examples where finite conductivity effects have important consequences, namely electrowetting of topographically structured surfaces as well as the generation of drops in AC electric fields. Finally, we review recent attempts to incorporate electrowetting into conventional channel-based microfluidic devices in order to enhance the flexibility of controlling the generation of drops.

[1]  Frieder Mugele,et al.  Electrical discharge in capillary breakup: controlling the charge of a droplet. , 2006, Physical review letters.

[2]  David Quéré,et al.  Non-sticking drops , 2005 .

[3]  Frieder Mugele,et al.  Hydrodynamic resistance of single confined moving drops in rectangular microchannels. , 2009, Lab on a chip.

[4]  Dagmar Steinhauser,et al.  Microfluidic mixing through electrowetting-induced droplet oscillations , 2006 .

[5]  Magalie Faivre,et al.  High-speed microfluidic differential manometer for cellular-scale hydrodynamics. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[6]  Aaron Wheeler,et al.  Putting Electrowetting to Work , 2008, Science.

[7]  Kwan Hyoung Kang,et al.  How Electrostatic Fields Change Contact Angle in Electrowetting , 2002 .

[8]  George M. Whitesides,et al.  Coding/Decoding and Reversibility of Droplet Trains in Microfluidic Networks , 2007, Science.

[9]  S. Quake,et al.  Microfluidics: Fluid physics at the nanoliter scale , 2005 .

[10]  Justin J. Cooper-White,et al.  The effect of elasticity on drop creation in T-shaped microchannels , 2006 .

[11]  Mohamed Abdelgawad,et al.  All-terrain droplet actuation. , 2008, Lab on a chip.

[12]  Stephan Herminghaus,et al.  Electroactuation of fluid using topographical wetting transitions. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[13]  S. Herminghaus,et al.  Self-excited oscillatory dynamics of capillary bridges in electric fields , 2003 .

[14]  S. Cho,et al.  Creating, transporting, cutting, and merging liquid droplets by electrowetting-based actuation for digital microfluidic circuits , 2003 .

[15]  Aa Anton Darhuber,et al.  PRINCIPLES OF MICROFLUIDIC ACTUATION BY MODULATION OF SURFACE STRESSES , 2005 .

[16]  S. Herminghaus,et al.  Electrostatic stabilization of fluid microstructures , 2002 .

[17]  Howard A. Stone,et al.  ENGINEERING FLOWS IN SMALL DEVICES , 2004 .

[18]  S. Herminghaus,et al.  Transport dynamics in open microfluidic grooves. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[19]  Dalton J. E. Harvie,et al.  Deformation of a viscoelastic droplet passing through a microfluidic contraction , 2008 .

[20]  G. Luo,et al.  Microfluidic approach for rapid interfacial tension measurement. , 2008, Langmuir : the ACS journal of surfaces and colloids.

[21]  H. Stone,et al.  Cellular-scale hydrodynamics , 2008, Biomedical materials.

[22]  A. I. Drygiannakis,et al.  On the connection between dielectric breakdown strength, trapping of charge, and contact angle saturation in electrowetting. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[23]  S. Vanapalli,et al.  Electrowetting --A versatile tool for controlling microdrop generation , 2008, The European physical journal. E, Soft matter.

[24]  Shuichi Takayama,et al.  Reversible switching of high-speed air-liquid two-phase flows using electrowetting-assisted flow-pattern change. , 2003, Journal of the American Chemical Society.

[25]  S. Herminghaus,et al.  Switching liquid morphologies on linear grooves. , 2007, Langmuir.

[26]  B. Berge,et al.  Limiting phenomena for the spreading of water on polymer films by electrowetting , 1999 .

[27]  Richard B. Fair,et al.  Digital microfluidics: is a true lab-on-a-chip possible? , 2007 .

[28]  J. Baret,et al.  Electrowetting: from basics to applications , 2005 .

[29]  Frieder Mugele,et al.  Electrowetting-controlled droplet generation in a microfluidic flow-focusing device , 2007 .

[30]  A. Papathanasiou,et al.  Illuminating the connection between contact angle saturation and dielectric breakdown in electrowetting through leakage current measurementsa) , 2008 .

[31]  Reinhard Lipowsky,et al.  Wetting morphologies at microstructured surfaces. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[32]  Kwan Hyoung Kang,et al.  A numerical investigation on AC electrowetting of a droplet , 2008 .

[33]  John Ralston,et al.  Electrowetting: a model for contact-angle saturation , 2000 .

[34]  N. Gershenfeld,et al.  Microfluidic Bubble Logic , 2006, Science.

[35]  K. Nichols,et al.  Electrowetting-based microdrop tensiometer. , 2008, Langmuir : the ACS journal of surfaces and colloids.

[36]  Stephan Herminghaus,et al.  Electrowetting: a convenient way to switchable wettability patterns , 2005 .

[37]  T. Jones,et al.  Frequency-dependent electromechanics of aqueous liquids: electrowetting and dielectrophoresis. , 2004, Langmuir : the ACS journal of surfaces and colloids.

[38]  Friedrich Gunther Mugele,et al.  Equilibrium drop surface profiles in electric fields , 2007 .

[39]  Helen Song,et al.  Reactions in droplets in microfluidic channels. , 2006, Angewandte Chemie.

[40]  Scaling of interface displacement in a microfluidic comparator , 2007 .

[41]  D. Ende,et al.  Electrowetting of complex fluids: perspectives for rheometry on chip. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[42]  H. Stone,et al.  Formation of dispersions using “flow focusing” in microchannels , 2003 .

[43]  Jianhong Xu,et al.  A new interfacial tension measurement method through a pore array micro-structured device. , 2009, Journal of colloid and interface science.

[44]  S. D. Hudson,et al.  Microfluidic interfacial tensiometry , 2005 .

[45]  Frieder Mugele,et al.  Electrowetting-enhanced microfluidic device for drop generation , 2008 .

[46]  Behrouz Abedian,et al.  Low voltage electrowetting using thin fluoroploymer films. , 2006, Journal of colloid and interface science.

[47]  John Ralston,et al.  Contact angle saturation in electrowetting. , 2005, The journal of physical chemistry. B.

[48]  D. Saville.  ELECTROHYDRODYNAMICS:The Taylor-Melcher Leaky Dielectric Model , 1997 .

[49]  Stephan Herminghaus,et al.  Interface profiles near three-phase contact lines in electric fields. , 2003, Physical review letters.

[50]  G. Whitesides,et al.  Oscillations with uniquely long periods in a microfluidic bubble generator , 2005 .

[51]  Anke Klingner,et al.  Capillary bridges in electric fields. , 2004, Langmuir : the ACS journal of surfaces and colloids.

[52]  R. Fair,et al.  Electrowetting-based actuation of liquid droplets for microfluidic applications , 2000 .

[53]  N. Nguyen,et al.  Microfluidic sensor for dynamic surface tension measurement , 2006 .

[54]  A parametric study of droplet deformation through a microfluidic contraction: Shear thinning liquids , 2007 .