Low-Noise Electronic Readout for High-Throughput, Portable Biomolecular Detection in Microchannel Arrays

We have developed a new label-free detection method where specific biomolecules adsorb to the walls of a suspended microchannel resonator, or simply flow through and thereby lower its resonant frequency. The oscillation of the microchannel is measured optically by reflecting a laser beam off the channel surface and detecting its position with a photo-sensitive detector. While the optical readout is sensitive and simple to implement for single microchannels, it is less suitable for arrays since multiple laser beams and detectors must be carefully aligned for each microchannel. In contrast, the electronic readout described in this thesis is highly scalable, extremeley robust, suitable for mass production and point-of-care devices outside of the laboratory. We have investigated a variety of readout methods including capacitive amplitude sensing and strain gauges, for high signal-to-noise frequency detection that compensates for large parasitic capacitances. Implementation of capacitive detection methods result in large parasitics, indicating that piezoresistive strain gauges present the most promising solution. Integration of the piezoresistors directly on the sensors provides a one-chip solution, eliminating parasitic capacitances introduced when using multiplechip solutions. Once the electrical readout is optimized, for surface-based affinity assays we expect results comparable to fluorescent readout of protein microarrays. Thesis Supervisor: Scott Manalis Title: Associate Professor