Fabrication and Characterization of an Integrated Microsystem for Biomolecular Preconcentration and Sensing

1 We report on a fabrication and packaging process for a microsystem consisting of a mass-based 2 protein detector and a fully integrated preconcentrator. Preconcentration of protein is achieved 3 by means of a nanofluidic concentrator, which takes advantage of fast non-linear electro-osmotic 4 flow near a nanochannel-microchannel junction to concentrate charged molecules inside a 5 volume of fluid on the order of one picoliter. Detection of preconcentrated protein samples is 6 accomplished by passing them through a suspended microchannel resonator, which is a hollow 7 resonant cantilever serially connected to the nanofluidic concentrator on the same device. The 8 transit of a preconcentrated sample produces a transient shift in the cantilever’s resonance 9 frequency proportional to the density of the sample, and hence the concentration of protein 10 contained in it. A device containing both nanofluidic concentrator and suspended microchannel 11 resonator structures was produced using a novel fabrication process which simultaneously 12 satisfies the separate packaging requirements of the two structures. Initial testing of this 13 prototype device has demonstrated that the integrated suspended microchannel resonator can 14 accurately measure the concentration of a bovine serum albumin sample which was 15 preconcentrated using the integrated nanofluidic concentrator. Future improvements in the 16 fabrication process will allow site-specific surface modification of the device and compatibility 17 with separation methods, which will create opportunities for its application to immunoassays and 18 universal detection. 19