Multilayered microfluidic probe heads

Microfluidics have emerged as powerful processing and analytical tools. However, as they are usually closed systems, they are difficult to use with large samples and surfaces that cannot pass inside their conduits. Here, we extend our previously reported microfluidic probe (MFP) concept, in which a focused stream of liquid is scanned over a surface, for which heads were fabricated using one Si wafer and a molded poly(dimethylsiloxane) (PDMS) block. The new heads comprise a microfabricated Si lid, a chip for hydrodynamic flow confinement (HFC) and standard ports and fittings. The HFC chip carries the smallest structures needed for focusing the liquid on the surface; the Si lid is bonded to the HFC chip using a polyimide adhesive and has macroscopic vias for bonding standard ports and fittings. These heads are easy to fabricate at high yield, have high-resolution potential and are compatible with a large number of chemicals and solvents. We exemplify this by patterning proteins on a surface, directly developing a resist using a high-pH developer, and producing tapered structures in a resist. This work should foster the adoption of MFPs for processing, patterning and analyzing surfaces under microfluidic conditions. © 2009 IOP Publishing Ltd.