High-pressure microfluidic control in lab-on-a-chip devices using mobile polymer monoliths.

We have developed a nonstick polymer formulation for creating moving parts inside of microfluidic channels and have applied the technique to create piston-based devices that overcome several microfluidic flow control challenges. The parts were created bycompletely filling the channels of a glass microfluidic chip with the monomer/ solvent/initiator components of a nonstick photopolymer and then selectively exposing the chip to UV light in order to define mobile pistons (or other quasi-two-dimensional shapes) inside the channels. Stops defined in the substrate prevent the part from flushing out of the device but also provide sealing surfaces so that valves and other flow control devices are possible. Sealing against pressures greater than 30 MPa (4,500 psi) and actuation times less than 33 ms are observed. An on-chip check valve, a diverter valve, and a 10-nL pipet are demonstrated. This valving technology, coupled with high-pressure electrokinetic pumps, should make it possible to create a completely integrated HPLC system on a chip.