Bilayer membranes in micro-fluidics: from gel emulsions to soft functional devices

TL;DR

This paper presents a novel approach to creating self-assembled, stable bilayer membrane structures within microfluidic devices, enabling new functionalities for soft matter devices and chemical processing.

Contribution

It introduces a method for forming stable, self-assembled bilayer membranes in microfluidics that can be functionalized and used for electronic, chemical, and structural applications.

Findings

Membranes form spontaneously in high volume fraction emulsions.

Membranes remain stable during microfluidic pumping.

Membranes can be functionalized with molecules or used as coupling media.

Abstract

We outline a concept of self-assembled soft matter devices based on micro-fluidics, which use surfactant bilayer membranes as their main building blocks, arrested in geometric structures provided by top-down lithography. Membranes form spontaneously when suitable water-in-oil emulsions are forced into micro-fluidic channels at high dispersed-phase volume fractions. They turn out to be remarkably stable even when pumped through the micro-fluidic channel system. Their geometric arrangement is self-assembling, driven by interfacial energy and wetting forces. The ordered membrane arrays thus emerging can be loaded with amphiphilic functional molecules, ion channels, or just be used as they are, exploiting their peculiar physical properties. For wet electronic circuitry, the aqueous droplets then serve as the 'solder points'. Furthermore, the membranes can serve as well-controlled coupling media between chemical processes taking place in adjacent droplets. This is shown for the well-known Belousov-Zhabotinski reaction. Suitable channel geometries can be used to (re-) arrange the droplets, and thereby their contents, in a controlled way by just moving the emulsion through the device. It thereby appears feasible to construct complex devices out of molecular-size components in a self-assembled, but well controlled manner.