Microfluidic devices could significantly reduce the size and cost of many laboratory assays. However, many biological assays need a gas/liquid interface, limiting the usefulness of current devices in which reagents flow in enclosed channels. To overcome this limitation, Bin Zhao and colleagues from the University of Illinois at Urbana-Champaign (Urbana, IL) have developed a technique for creating devices with “virtual walls” (Science 291, 1023–1026, 2001). The researchers first created a “sandwich” of two glass slides supported by coverslips, coating the inner layers with a hydrophobic self-assembled monolayer (SAM). A photoresistant template is placed on top of the slide, which is then irradiated with ultraviolet (UV) light. The UV light degrades the molecules on the surface of the monolayer, creating a hydrophilic surface. When an aqueous solution is injected between the slides, the fluid flows between the hydrophilic “tracks” on the surface of the slides. Team leader David Beebe says that the next step is to develop a prototype device with which they can carry out a bioassay. The device is particularly well suited for studies of gas–liquid interactions, such as the exchange of substances in lung tissue.
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Barlow, J. Virtual walls for microfluidics. Nat Biotechnol 19, 319 (2001). https://doi.org/10.1038/86697