Floating electrode electrowetting on hydrophobic dielectric. Here we focus on a simple, dielectricfree approach to electrowetting using. Electrowettingondielectric actuation of a spatial and angular manipulation mems stage daniel j. Despite these advantages, the electrowetting based liquid lenticular lens demands high driving voltage and low breakdown voltage with a single dielectric layer structure. Analysis and measurement of forces in an electrowetting driven oscillator nathan brad crane1, alex a volinsky1, vivek ramadoss1, michael nellis 1, pradeep mishra1, and xiaolu pang1,2 1department of mechanical engineering, university of south florida, 4202 e. Electrohydrodynamic analysis of electrowettingondielectric ewod. A low voltage, twolevelmetal, and multilayer insulator electrowettingondielectric ewd platform is presented. A first transparent electrode is disposed on the first substrate. Electrowetting on dielectric has been demonstrated in various configurations with different materials, but the basic components of ewod are electrodes, a thin hydrophobic insulator, and an electrically conductive liquid. Electrowetting is the process of altering the wetting properties of a liquid on a surface with an electric field. Volinsky department of mechanical engineering, university of south florida, tampa, florida 33620, usa.
Tong microscale water droplet motions in parallelplate electrowetting ondielectric ewod devices including transport, splitting, merging and dispensing have been numerically studied. Electrowetting ondielectric ewod is a surfacewetting phenomenon resulting from electrical control of the surface wetting properties through the application of an electric potential. Effective cooling of integrated circuits using liquid. Electrowetting on dielectrics on lubricating fluid based. First, a practical droplet speed measurement method has been methodically demonstrated and some related velocity terms have been introduced. In many applications the solid surface consists of a thin dielectric deposited onto a conducting layer. Statistical modeling of electrowettinginduced droplet. Electrowettingondielectric induced droplet actuation in. Dropletbased label free detection system based on guidedmode resonance and electrowettingondielectric for concentration measurement yingbin wang, linyun su, chingshu fu, chengsheng huang, and wensyang hsu. A certain degree of thickness of the dielectric layer is essential for a uniform operation and. Floating electrode electrowetting on hydrophobic dielectric with an sio 2 layer mehdi khodayari, benjamin hahne, nathan b. The electrowetting ondielectric ewod lens is a good candidate for dynamic beamshaping optics for advanced solidstate lighting systems. The electrowetting display includes a first substrate and an opposing second substrate with a polar fluid layer and a color nonpolar fluid layer interposed therebetween.
Electrowetting on dielectric ewod allows us to control wettability of droplets on a solid surface using electrical inputs and has been used in a wide range of applications including microfluidics, optical displays, lenses, and others. When the characteristic dimension of a droplet is lower than the capillary length. Fluid dynamics of an electrowettingondielectrics tube. Pdf low voltage electrowettingondielectric researchgate. Droplet velocity in an electrowetting on dielectric.
The required voltage can be reduced by increasing the dielectric constant and decreasing the thickness of the dielectric layer, thus increasing the capacitance of the. Digital microfluidics with electrowetting softmatter. Here, high frequency mhz electric fields are used to exploit the fact that an electric field gradient produces a force on a dipole. While ew is controlling wettability of a certain electrolyte on a metal electrode by varying electric energy across the electrical. Partially wetting liquid droplet at zero voltage dashed and at high voltage solid. Digital microfluidics based on electrowetting on dielectric ewod devices has. This paper deals with electrowetting ew and electrowetting ondielectric ewod principles applied to microfluidic devices. Low voltage electrowettingondielectric article pdf available in journal of applied physics 927 october 2002 with 2,750 reads how we measure reads. A second electrode is disposed on the second substrate. Modeling the fluid dynamics of electrowetting on dielectric ewod article pdf available in journal of microelectromechanical systems 154. Dispensing 300pl droplets from 140nl closed on chip reservoirs was accomplished with as little as 11. Author links open overlay panel junghoon lee a hyejin moon b jesse fowler b thomas schoellhammer c changjin kim b. Sep 18, 2002 typically, much higher voltages 100 v are used to change the wettability of an electrolyte droplet on a dielectric layer compared with a conductive layer.
This paper deals with electrowetting ew and electrowetting on dielectric ewod principles applied to microfluidic devices. In eq 17, e d is the uniform electric field in the dielectric layer. Wirelessly powered electrowettingondielectric ewod by. Reversible ultralowvoltage liquidliquid electrowetting. Numerical and theoretical analyses of the dynamics of. Electrowetting on dielectric digital microfluidics for 3dimensional cell culture and chemical screening by subin mac george presented to the faculty of the graduate school of the university of texas at arlington in partial fulfillment of the requirements for the degree of doctor of philosophy the university of texas at arlington. Water or aqueous electrolytes are the dominant components in electrowetting on dielectric ewodbased microfluidic devices. Analysis and measurement of forces in an electrowetting. Electrowetting on dielectric ewod is a unique method of moving small volume droplets in microfluidic biochips that relies on modification of surface wetting characteristics using electrical methods. The model approximates the meniscus geometry as being a part of a compound. We have fabricated a fullyflexible, focustunable microlens array on a sheet and demonstrated its imaging capabilities. Increased droplet coalescence using electrowetting on.
Finally, a 100 nm layer of teflon was spincoated to act as the hydrophobic layer. Pdf modeling the fluid dynamics of electrowetting on. Ewod allows us to manipulate tiny droplets typically smaller than a microliter in volume as well as fluid interfaces on arrays of dielectric covered electrodes. In ew on dielectric ewod actuations, the microliter drops are usually placed between two. A lowcost and highresolution capacitivetodigital converter integrated circuit is used for droplet position detection in a digital microfluidic system. Electrowetting on this dielectric coated surface is called electrowetting on dielectric ewod to distinguish it from the conventional electrowetting on the bare electrode. Kharea adepartment of physics, indian institute of technology kanpur, kanpur208016, india bhindustan unilever research centre, banglore560066, india email. Us7760420b2 color electrowetting display ewd devices. In these cases, liquid is in direct contact with air. Current commercialization status of electrowetting ondielectric ewod digital microfluidics electrowetting on ewod surface. Dynamic contact angles and hysteresis under electrowetting. Fast switching response and low power consumption of electric actuation of surface tension has made electrowetting a promising. Ewod is used as on chip micropumping scheme for moving fluid digitally in lab on achip devices.
The reliability of an automated microfluidic system. Mnt liquid pixel based on electrowetting on dielectric. Sep 21, 2010 a low voltage, twolevelmetal, and multilayer insulator electrowetting on dielectric ewd platform is presented. Electrowetting on dielectric devices uses a conducting water and insulating oil liquid phase in conjunction on a dielectric layer. These challenges generally relate to preparing the surface that interfaces with droplets a dielectric material on the electrodes and the top most hydrophobic coating that interfaces with the droplets.
This is the concept that has also become known as electrowetting on dielectric ewod. Modeling of droplet and bubble detachment assisted by. In ewod, the capacitance per unit area is determined by 0 t, where and t are the relative dielectric constant and thickness of dielectric materials, respectively, and 0 is the permittivity of free space. The alternative use of ionic liquids ils as electrowetting agents in ewod. This influence of the variation of the dielectric film elasticity on droplet electrowetting is best understood from free energybased consideration, leading to a test of the applicability of the classical lippmannyoung model. Our present study aims to characterize and study droplet speed in a typical ewod device. Pdf basics and applications of electrowetting on dielectric ew. We report electrowetting on dielectric ewod experiments using graphene. Droplet movement by electrowetting on dielectric ewod in a heleshaw cell is analysed theoretically and numerically. Electrowetting on paper for electronic paper display acs.
The extent of electrowetting reduces with decreasing elasticity of the dielectric elastomer film. Electrowetting ondielectric ewod, which is based on changing the wettability of liquids on a dielectric solid surface by varying the electric potential. Electrowetting using an insulating layer on top of a bare electrode was later studied by bruno berge in 1993. A formulation distinct from that developed for electrowetting on dielectric. Pdf electrowettingondielectric by wireless powering.
This method offers advantages over conventional continuousflow microfluidic chips, by way of significantly reduced sample size, as well as reconfigurability and scalability of architecture. Electrowetting on dielectric ewod, pioneered by berge in 1996, has come to be the dominant method of electrowetting and currently has a use in a wide range of technologies including liquid lenses, low. Permittivity of free space contact angle under applied voltage. On top of it lies the electrolyte, surrounded by air or another medium.
Electrowetting can be demonstrated by replacing the metal electrode in the ewod system by a semiconductor. Flexible electrowettingondielectric microlens array sheet. Zangari1,a 1department of materials science and engineering, university of virginia, charlottesville, virginia 22904, usa 2department of chemical engineering, university of virginia, charlottesville, virginia 22904, usa. In these devices, the wetting properties of the liquid phases. A lowcost and highresolution droplet position detector for. Reversible contact angle changes were observed on the tefloncoated graphene electrode with.
Ewod is used as onchip micropumping scheme for moving fluid digitally in labonachip devices. This method of actuation is well known but less common in digital microfluidics due to problems with heating. Electrowetting on dielectric ewod uses an insulating layer over the electrodes to prevent electrolysis of the liquid 1. Several categories of paper have been investigated for this purpose, with the surface coating, roughness, thickness, and.
In this paper, we will investigate two more types of electrocapillary principles and demonstrate feasibility for mems. A computational model for the design of electrowetting on. In this masters thesis, a liquid pixel based on electrowetting is theoretically studied, fabricated, and tested in the laboratory, so as to assess its usability as a light steering device. Latticeboltzmann simulations of electrowetting phenomena. Pdf electrowetting on dielectric experiments using. Electrowetting is a phenomenon by which the wettability of a surface is manipulated with an electric eld. On the relationship of dielectrophoresis and electrowetting.
In this wiki entry, i will not focus on this force. The free energy f of a droplet is a functional of the droplet shape. The motive force is due to the response of the free electric surface charge to the electric field. Low voltage electrowettingondielectric platform using multi. Electrowetting ondielectric ewod is one of the most flexible and promising methods to control the wettability of liquids by using externally applied electrical potential 12. Some researchers tested other dielectric materials or electrolytes to. Reducing voltage requirements for microfluidics fusayo saeki1, jean baum1, hyejin moon2, jeongyeol yoon3, changjin cj kim2 and robin l. We study the fluid dynamics of polar highk fluids immersed in nonpolar insulating fluids, excited by electrowetting on dielectric ewod forces inside a tube with pressure compensation channels. Electrowetting can be demonstrated by replacing the metal. Current commercialization status of electrowettingon. Electrowetting ew effect is defined as changing in the interfacial energy of solidliquid interface which causes to change in solidliquid contact angle. Electrowetting on dielectric experiments using graphene. In many electrowetting on dielectric ewod based microfluidics devices, droplet actuation speed is a crucial performancecontrolling parameter. Pdf electrowetting on dielectric experiments using graphene.
Electrowetting of sessile drops on soft dielectric elastomer. Basics and applications of electrowetting on dielectric ew. Oct 25, 2010 the use of paper as a material for various device applications such as microfluidics and energy storage is very attractive given its flexibility, versatility, and low cost. Threedimensional computer animation of an electrowetting. Dielectric breakdown of several typical polymeric and inorganic insulators employed as dielectrics for ewod has been analytically investigated.
Dielectric breakdown and failure of anodic aluminum oxide. Electrowetting on dielectrics for manipulating oil drops and gas bubbles in aqueousshell compound d duration. This concept is now known as electrowetting on dielectric ewod, which is the con guration that is mainly used for present developments. Pcb printed circuit board substrate electrowetting devices are low cost and quickly fabricated, and they can be placed easily with digital controlling systems. Low voltage electrowettingondielectric for microfluidic. A fundamental study on electrowetting by traditional and. Wirelessly powered electrowettingondielectricewod d. Volinsky department of mechanical engineering, university of south florida, tampa fl 33620, usa floating electrode electrowetting is caused by dc voltage applied to a liquid droplet on the cytop. Preston1, ariel anders,2, banafsheh barabadi,1, evelyn tio1, yangying zhu1, dingran annie dai1, evelyn n. For enabling this scheme, stacked deposition of thin dielectric and hydrophobic layer in that order between microchannel and electrodes is done. Electrowetting ew and electrowetting on dielectric ewod can be used to handle aqueous liquid in microscale without any second liquid medium.
Electrowetting of sessile drops on soft dielectric. The simplest electrowetting situation, used widely in many ewoc and ewod setups, is the spreading of a droplet of conductive liquid on a solid in the presence of an ambient dielectric fluid. We propose a simple theoretical model for the motion, which describes well the voltage dependency of droplet speed below the saturation voltage as measured experimentally. Simulation and experimentation of a microfluidic device. Micromachines free fulltext flexible electrowettingon. Electrowetting ondielectric ewod is arguably the most flexible and powerful tool, used in many loc platforms because there is no need for a closed channel network and external pump to manipulate the droplets or mechanical parts to move or guide the droplets 23456. Oct 20, 2010 liquid droplet movement with electrowetting. Electrowetting 2018 university of twente research information. Electrowetting is a commonly used tool to manipulate sessile drops on hydrophobic surfaces. While ew is controlling wettability of a certain electrolyte on a metal electrode by varying electric energy across the electrical double layer edl, ewod. Zangari1,a 1department of materials science and engineering, university of virginia, charlottesville, virginia 22904, usa. Osa 3d model for rectangular electrowetting lens structures. Scaling electrowetting with printed circuit boards for.
The advantage of electrowetting is that it can provide a dynamic and adjustable. Volume 95, issues 23, 1 january 2002, pages 259268. Electrowetting ondielectric ewod based droplet actuation in microfluidic chip is designed and fabricated. Van grinsven 1, alireza ousati ashtiani 1,2 and hongrui jiang 1,2,3,4, 1 department of electrical and computer engineering, university of wisconsinmadison, madison, wi 53706, usa 2 department of materials science and engineering, university of wisconsinmadison, madison, wi 53706, usa. Each liquid lens of the array is individually tunable via electrowetting on dielectric ewod actuation and is situated on a polydimethylsiloxane pdms substrate, which allows the lens array to operate as a reconfigurable optical system. Dielectric materials for electrowettingondielectric actuation. Droplets are manipulated via the application of asymmetric electric fields 2. Reversible contact angle changes were observed on the tefloncoated graphene electrode with both ac and dc voltages. Electrowetting on dielectric ewod is a surfacewetting phenomenon resulting from. A lowcost and highresolution droplet position detector. Electrowetting on dielectric ewod based droplet actuation in microfluidic chip is designed and fabricated. Large changes in contact angle were observed for droplets on a dielectriccovered conductive substrate.
Electrowetting on dielectric ewod device with dimple structures. Pdf this article discusses and experimentally verifies how to lower the operating voltage that drives liquid droplets by the principle of. The electrowetting response of these bilayer structures was characterized by concurrently measuring contact angle and leakage current during stepped voltage measurements up to failure, showing three electrowetting response regimes. Improving the dielectric properties of an electrowettingondielectric. In electrowetting the balance of forces at the contact point is modified by the application of a voltage between a conducting fluid and the solid surface. Ew and ewod are principles that can control wettability of liquids on solid surfaces using electric potential. Here we demonstrate that electrowetting ew devices can be readily fabricated on paper substrates. In general, it involves the use of a substrate with electrodes that are insulated by a thin dielectric layer. By applying an external voltage over a liquid and a dielectric coated surface, one achieves a reduction of the macroscopic contact angles for increasing voltage. Low thermal stability, evaporation, and a propensity to facilitate corrosion of the metal parts of integrated circuits or electronics are drawbacks of aqueous solutions. Micromachines free fulltext flexible electrowetting. Ewod is a phenomenon where a voltage applied to a conducting liquid on a dielectric covered electrode causes the liquid to spread over the dielectric surface 14. Electrowettingondielectric ewod is the most widely accepted.
The induced interfacial shear flow can be used to move the droplets. A geometric approximation model is described to predict the meniscus shape of a rectangular ewod lens with arbitrary voltages and small bond numbers. Low voltage electrowetting lenticular lens by using. Pdf electrowetting on dielectric and superhydrophobic.
Electrowetting ondielectric ewod, in which microdroplets are manipulated using electrical inputs, has drawn a great deal of attraction with applications of digital labonachip and hotspot cooling. Electrowetting and electrowetting ondielectric for microscale liquid handling. Electrowetting on this dielectric coated surface is called electrowetting ondielectric ewod to distinguish it from the conventional electrowetting on the bare electrode. Dielectric breakdown and failure of anodic aluminum oxide films for electrowetting systems m. Electrowetting on dielectrics on lubricating fluid based slippery surfaces with negligible hysteresis j. Graphene sheets were synthesized by chemical vapor deposition, and transferred to various substrates including glass slides and pet films. This article discusses and experimentally verifies how to lower the operating voltage that drives liquid droplets by the principle of electrowetting on dielectric ewod. Dropletbased labelfree detection system based on guided. When the integration of eq 16 is performed, the result is then, according to the electrowetting model, the total heightofrise is note that the second term in eq 20 is. Pdf the shape of liquiddroplet on planar surfaces is mainly governed by resultant surface tension forces at. Plate electrowetting ondielectric ewod devices yin guan, phd the university of texas at arlington, 2015 supervising professor. The fluids are set in motion using the electrowetting effect resulting in a pressure difference inside the tube. Low voltage electrowettingondielectric platform using.
This dielectric layer is critical to the performance of ew systems, as it stores the electrostatic energy for droplet actuation. Walker and benjamin shapiro, member, ieee abstractthis paper discusses the modeling and simulation of a parallelplate electrowetting on dielectric ewod device that. Spontaneous electrowetting, in contrast, can arise using the parallel line electrode con. The amount of applicable voltage across the liquidmetal interface without current leakage is limited. Dispensing 300pl droplets from 140nl closed onchip reservoirs was accomplished with as little as 11. Electrowetting ondielectric the electrowetting effect describes the observable influence of an electric field on both bulk liquid motions and the contact angle. Pcb manufactured electrowetting arrays impose many challenges due to the irregularities from process and materials used.
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