All terrain droplet actuation

From Soft-Matter
Revision as of 17:54, 16 November 2009 by Burgess (Talk | contribs)

Jump to: navigation, search

Original Entry: Ian Bruce Burgess Fall 2009


Reference

M. Abdelgawad, S.L.S. Freire, H. Yang and A.R. Wheeler, Lab on a Chip 8, 672-677 (2008).

Summary

This paper introduces a new platform for droplet-based microfluidic manipulation on flexible substrates. Electrowetting forces are applied to drops via copper electrodes embedded in a flexible polyimide film. The electrodes are protected with coatings of poly(dimethylsiloxane) (PDMS) and teflon. Performance properties and applications of these devices are explored. Electrowetting forces were sufficiently strong to drive droplets with sufficiently small volume (<7.3<math>\mu L</math>) up a vertical incline. Droplet actuation in various configurations of the flexible substrate are shown in the figure below.

20%

A large significance of having a flexible platform for microfluidic droplet manipulation is that the device can easily be integrated across different environments. As an example, the authors demonstrate the transport of a water droplet containing the dye methylene blue and glucose across an air-oil interface into a bath of silicone oil. In an anaerobic environment, the dye is reduced and loses its color. They also demonstrate how the temperature of a droplet can be controlled easily using deformation of the chip. Using the same geometry, they then demonstrate effective purification of a water droplet containing oligonucleotides through liquid-liquid extraction of histones. This is accomplished by driving the droplet into a bath of a water-immiscible phenol solution and then returning it to the air after allowing diffusion of the histones into the phenol.

Soft-Matter Discussion

The significance of this paper from the point of view of soft-matter and our class material is that it demonstrates how electrowetting can be used to make practical devices. Fig. 1a shows how the voltages on the substrate are manipulated