Rapid Fabrication of Close-Typed Electrowetting on Dielectric Devices

Discrete flow microfluidic devices have been identified as a technology that can be used to efficiently deliver health care services by reducing the cycle times and reagent consumption of common biological protocols and medical diagnostic procedures while reducing overhead costs by performing these applications at the point of care. Electrowetting on dielectric is one promising discrete flow microfluidic platform that can individually create, manipulate, and mix droplets through the application of asymmetric electric fields. The work presented outlines fundamental and practical contributions to the understanding and advancement of electrowetting on dielectric devices that the authors are using to develop a device capable of performing immunoassays on chip. Explicit analytical models for capillary force and the reduction in that force by contact angle hysteresis as a function of the three-dimensional shape of the droplet were derived to develop an empirically validated analytical model for transient motion of droplets in electrowetting on dielectric devices. This model accurately predicts the maximum droplet displacement and travel time to within 2.3% and 2.7%, respectively; whereas the average droplet velocity was always predicted to within 8.1%. It also demonstrates a method for real time monitoring of droplet composition, particle concentration, and chemical reactions in electrowetting on dielectric devices without optical access. This method has been used to determine the concentration of water-methanol solutions, measure the concentration of glass microspheres at various concentrations, and detect the chemical reactions that are typically used in immunoassays. A method for the mechanical filtration of droplets in these devices will also be presented. The proposed filtration method was successful at pore sizes at least two orders of magnitude below the droplet height, which is small enough to separate red and white blood cells in continuous flow microfluidic devices.

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An Empirically Validated Analytical Model of Droplet Dynamics in Electrowetting on Dielectric Devices

Langmuir ◽

10.1021/la103702t ◽

2010 ◽

Vol 26 (24) ◽

pp. 19230-19238 ◽

Cited By ~ 25

Author(s):

M. J. Schertzer ◽

S. I. Gubarenko ◽

R. Ben-Mrad ◽

P. E. Sullivan

Keyword(s):

Analytical Model ◽

Droplet Dynamics ◽

Electrowetting On Dielectric ◽

Dielectric Devices

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Reversible ultralow-voltage liquid–liquid electrowetting without a dielectric layer

Faraday Discussions ◽

10.1039/c7fd00016b ◽

2017 ◽

Vol 199 ◽

pp. 63-73 ◽

Cited By ~ 5

Author(s):

Nico E. A. Cousens ◽

Anthony R. J. Kucernak

Keyword(s):

Surface Roughness ◽

Electrolyte Concentration ◽

Solid Metal ◽

Electrolyte Composition ◽

Operating Voltage ◽

Reversible Change ◽

Electrowetting On Dielectric ◽

Theoretical Predictions ◽

Dielectric Devices ◽

First Time

Electrowetting-on-dielectric devices typically have operating voltages of 10–20 V. A reduction in the operating voltage could greatly reduce the energy consumption of these devices. Herein, fully reversible one-electrolyte electrowetting of a droplet on a solid metal surface is reported for the first time. A reversible change of 29° for an 800 mV step is achieved. The effects of surface roughness, electrolyte composition, electrolyte concentration and droplet composition are investigated. It was found that there is a dramatic dependence of the reversibility and hysteresis of the system on these parameters, contrary to theoretical predictions. When a 3-chloro-1-propanol droplet is used, a system with no hysteresis and a 40° change in angle are obtained.

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Counterbalanced Valve Metal Oxide as a Reliable Dielectric Layer for Electrowetting-on-dielectric Devices

Sensors and Materials ◽

10.18494/sam.2019.2449 ◽

2019 ◽

Vol 31 (9) ◽

pp. 2861

Author(s):

Supin Chen ◽

Chang-Jin �gCJ�h Kim

Keyword(s):

Metal Oxide ◽

Dielectric Layer ◽

Electrowetting On Dielectric ◽

Valve Metal ◽

Dielectric Devices

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Biocompatible/Biodegradable Electrowetting on Dielectric Microfluidic Chips with Fluorinated CTA/PLGA

Materials ◽

10.3390/ma11081332 ◽

2018 ◽

Vol 11 (8) ◽

pp. 1332 ◽

Cited By ~ 1

Author(s):

Kaidi Zhang ◽

Lei Chao ◽

Jia Zhou

Keyword(s):

Contact Angle ◽

Photoelectron Spectroscopy ◽

Contact Angle Hysteresis ◽

Cellulose Triacetate ◽

Microfluidic Chips ◽

Electrowetting On Dielectric ◽

Force Microscopy ◽

Atomic Force ◽

Dielectric Devices ◽

Contact Line Pinning

One of the major hurdles in the development of biocompatible/biodegradable EWOD (Electrowetting-on-dielectric) devices is the biocompatibility of the dielectric and hydrophobic layers. In this study, we address this problem by using reactive ion etching (RIE) to prepare a super-hydrophobic film combining fluorinated cellulose triacetate (CTA) and poly (lactic-co-glycolic acid) (PLGA). The contact angle (CA) of water droplets on the proposed material is about 160°. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) characterizations indicate that a slight increase in the surface roughness and the formation of CFx (C-F or CF2) bonds are responsible for the super-hydrophobic nature of the film. Alternating Current (AC) static electrowetting and droplet transportation experiments evidence that contact angle hysteresis and contact line pinning are greatly reduced by impregnating the CTA/PLGA film with silicon oil. Therefore, this improved film could provide a biocompatible alternative to the typical Teflon® or Cytop® films as a dielectric and hydrophobic layer.

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