Patterning microfluidic device wettability using flow confinement

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Original entry: Darren Yang, AP225, Fall 2010

Reference

A.R. Abate, J. Thiele, M. Weinhart, D.A. Weitz, “Patterning microfluidic device wettability using flow confinement,” Lab on a Chip, 10, 14 (2010).

Keyworks

Monodisperse Double Emulsions, Multiple Emulsions, Poly(Dimethylsiloxane),

Summary

The authors present a versatile method to spatially pattern the surface properties of microfluidic devices using flow confinement. This technique allows surface patterning with micron-scale resolution, and to demonstrate its effectiveness, they use it to pattern wettability to form Water/Oil/Water and Oil/Water/Oil double emulsions.

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Background

The formation of multiple emulsions, which consist of large drops with smaller drops inside, requires microfludics channels with patterned surface properties. The current methods to spatially pattern the wettability of microfluidics devices are difficult to use and of limited versatility. For example, one of the current approaches uses a polymerization reaction that is initiated by exposure to ultraviolet (UV) light to specific part of the channels. However, since micron-scale resolution is required, sophisticated optics and a powerful UV-light source are needed.

In this paper, the authors present an alternative method for patterning surface wettability that is versatile and easy to use. First they use an inert fluid to physically confine a chemical treatment that alters wettability in selected regions of the microfluidic channel. Since spatial control is achieved by physical confinement of the reaction, this chemical treatment method allowing many different surface treatments to be used.

To illustrate novel technique, the authors use photo-initiated and thermal-initiated surface treatments. Specifically, they demonstrate the effectiveness of this chemical treatment method by patterning the wettability of microfluidics devices to form both Water/Oil/Water and Oil/Water/Oil double emulsions.

Results