Microfiber-directed boundary flow in press-fit microdevices fabricated from self-adhesive hydrophobic surfaces.

We report a rapid microfluidic device construction technique which does not employ lithography or stamping methods. Device assembly physically combines a silicon wafer, an elastomer (poly(dimethylsiloxane) (PDMS)), and microfibers to form patterns of hydrophobic channels, wells, elbows, or orifices that direct fluid flow into controlled boundary layers. Tweezers are used to place glass microfibers in a defined pattern onto an elastomeric (PDMS) hydrophobic film. The film is then manually pressed onto a hydrophobic silicon wafer, causing it to adhere to the silicon wafer and form a liquid-tight seal around the fibers. Completed in 15 min, the technique results in an operable microdevice with micrometer-scale features of nanoliter volume. Microfiber-directed boundary flow is achieved by use of the surface wetting properties of the hydrophilic glass fiber and the hydrophobicity of surrounding surfaces. The simplicity of this technique allows quick prototyping of microfluidic components, as well as complete biosensor systems, such as we describe for the detection of pathogenic bacteria.