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Digital Microfluidic System with Vertical Functionality

Department of Bioengineering, University of California, Los Angeles, CA 90095, USA
Department of Chemistry & Biochemistry, University of California, Los Angeles, CA 90095, USA
Author to whom correspondence should be addressed.
Academic Editors: Andrew deMello and Xavier Casadevall i Solvas
Micromachines 2015, 6(11), 1655-1674;
Received: 1 September 2015 / Revised: 19 October 2015 / Accepted: 27 October 2015 / Published: 4 November 2015
(This article belongs to the Special Issue Droplet Microfluidics: Techniques and Technologies)
PDF [2137 KB, uploaded 4 November 2015]


Digital (droplet) microfluidics (DµF) is a powerful platform for automated lab-on-a-chip procedures, ranging from quantitative bioassays such as RT-qPCR to complete mammalian cell culturing. The simple MEMS processing protocols typically employed to fabricate DµF devices limit their functionality to two dimensions, and hence constrain the applications for which these devices can be used. This paper describes the integration of vertical functionality into a DµF platform by stacking two planar digital microfluidic devices, altering the electrode fabrication process, and incorporating channels for reversibly translating droplets between layers. Vertical droplet movement was modeled to advance the device design, and three applications that were previously unachievable using a conventional format are demonstrated: (1) solutions of calcium dichloride and sodium alginate were vertically mixed to produce a hydrogel with a radially symmetric gradient in crosslink density; (2) a calcium alginate hydrogel was formed within the through-well to create a particle sieve for filtering suspensions passed from one layer to the next; and (3) a cell spheroid formed using an on-chip hanging-drop was retrieved for use in downstream processing. The general capability of vertically delivering droplets between multiple stacked levels represents a processing innovation that increases DµF functionality and has many potential applications. View Full-Text
Keywords: digital microfluidics; EWOD; vertical functionality; hydrogel; sieve; spheroid; embryoid body digital microfluidics; EWOD; vertical functionality; hydrogel; sieve; spheroid; embryoid body

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Bender, B.F.; Garrell, R.L. Digital Microfluidic System with Vertical Functionality. Micromachines 2015, 6, 1655-1674.

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