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Single-Sided Apparatus For Manipulating Droplets By Electrowetting-On-Dielectric Techniques

Inactive Publication Date: 2008-07-17
STRATOS BIOSYST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0012]In brief, the present invention relates to a single-sided electrowetting-on-dielectric apparatus useful for microfluidic laboratory applications. In particular, the present

Problems solved by technology

Charge accumulates at the liquid-solid interface, leading to an increase in surface wettability and a concomitant decrease in the liquid-solid contact angle.
In practice, the fabrication of reliable single-sided electrowetting-on-dielectric devices having the configurations disclosed in the foregoing references has proven far more difficult than anticipated.
This requirement has proven problematic in reduction to practice, in that maintaining adhesion between a fluoropolymer hydrophobic coating and both the surface of a dielectric film and the surface of metallic ground electrode lines (which are not covered by the dielectric film) is particularly difficult.
More specifically, this problem results from the properties of fluoropolymers which limit their adhesion with respect to most metals.
This issue is further exacerbated when conformal hydrophobic coatings are employed, in that microscopic ridges on the surface of such a device negatively impact smooth droplet transport and often result in sites of dielectric breakdown and electrolysis.

Method used

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  • Single-Sided Apparatus For Manipulating Droplets By Electrowetting-On-Dielectric Techniques
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  • Single-Sided Apparatus For Manipulating Droplets By Electrowetting-On-Dielectric Techniques

Examples

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example 1

Fabrication of a Representative Single-Sided Electrowetting-on-Dielectric Apparatus

[0056]A representative single-sided electrowetting-on-dielectric apparatus was fabricated according to the following method.

[0057]The surface of a 4″ silicon wafer was exposed to wet O2 / N2 at 1045° C. for 45 min to prepare a thermal oxide (2500 Å) insulator film thereon. A first metal conductive layer (i.e., control electrode elements and interconnects), comprised of 60 Å of Ti / W, 300 Å of Au and 60 Å of Ti / W was then sputtered onto the thermal oxide insulator film surface. A first photoresist was then spin-coated and patterned by contact printing to define the electrode pattern. The first metal conductive layer was then wet etched at room temperature employing the following sequence: (1) 30% H2O2 in TFA for 90 sec; (2) 30% H2O2 for 30 sec; and (3) 30% H2O2 in TFA for 90 sec. The first photoresist layer was then stripped using reagent EKC830 for 10 min followed by reagent AZ300 for 5 min. The resultin...

example 2

Use of a Representative Single-Sided Electrowetting-on-Dielectric Apparatus

[0058]FIGS. 8a through 8d show sequential photographs of the one-dimensional transport of a droplet on the surface of a representative apparatus of the present invention. The apparatus was fabricated on the surface of a 4″ silicon wafer. The control electrode elements measured 1.5 mm square and were 250 Å thick (200 Å of gold over 50 Å of Ti / W). Gaps between adjacent control electrode elements measured 75 microns. The width of the ground electrode elements were 50 microns and the ground electrode elements were 250 Å thick (200 Å of gold over 50 Å of Ti / W). The first and second dielectric films were 1200 Å of silicon nitride (first dielectric film) and 500 Å of silicon dioxide (second dielectric film). The surface of the apparatus was spin-coated with 500 Å of CYTOP amorphous fluorocarbon polymers to render it electrowetting-compatible. Electrowetting actuation at 20 Hz (AC) occurred at 16 volts for a water dr...

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Abstract

A single-sided electrowetting-on-dielectric apparatus, which is useful for microfluidic laboratory applications, is disclosed. The apparatus comprises a substrate, an array of control electrode elements disposed on the substrate, a first dielectric film disposed on, and overlaying, the substrate and tie array of control electrode elements, at least one ground electrode element disposed on the first dielectric film, a second dielectric film disposed on, and overlaying, the first dielectric film and the at least one ground electrode element, and an electrowetting-compatible surface film disposed on the second dielectric film. A method of making the apparatus is also disclosed.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates generally to an apparatus for droplet-based liquid handling in laboratory-on-a-chip applications, and more specifically to a single-sided apparatus for manipulating droplets by electrowetting-on-dielectric techniques.[0003]2. Description of the Related Art[0004]In recent years, the principle of electrowetting-on-dielectric has attracted considerable interest for droplet-based liquid handling in laboratory-on-a-chip applications. Electrowetting-on-dielectric involving aqueous samples requires that a droplet rest on a surface or in a channel coated with a hydrophobic material. The surface is modified from hydrophobic to hydrophilic by applying a voltage between the liquid droplet and an electrode residing under a dielectric film surface layer. Charge accumulates at the liquid-solid interface, leading to an increase in surface wettability and a concomitant decrease in the liquid-solid contact ...

Claims

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Application Information

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IPC IPC(8): C25B11/00
CPCB01F13/0059B01F13/0076B01F13/0086Y10T29/417B01L2300/0816B01L2300/089B01L2400/0427B01L3/502792B01F33/3031B01F33/30352B01F33/30
Inventor MCRUER, ROBERT N.STOLOWITZ, MARK L.
Owner STRATOS BIOSYST