Electrically Addressed Dual Resonator Sensing Platform for Biochemical Detection

Chemically functionalized silicon microresonators provide the potential for sensitive, label-free biomolecular detection by coupling small induced perturbations in stiffness, mass, and dissipation due to surface bound analyte to their measured frequency response. However, several implementation challenges arise from the necessity of operation in compatible biological buffer solutions. These challenges include minimizing undesired effects of fluid-structure interaction and buffer interference with signal transduction. In this paper, we present a novel dual resonator sensing platform (DRP) to address these challenges, wherein electrical transduction and biochemical sensing are spatially separated onto two different mechanically coupled resonators. This enables electrical interrogation of the sensor without compromising the sensing environment, allowing for relative ease of fabrication and the possibility of integration with on-chip electronics. We demonstrate the functionality of the DRP as a mass sensing platform, with a mass responsivity of 34 Hz/ng in air. The viscous effects on dynamic response of the DRP were investigated by comparing the measurements with theoretical values, and a quality factor of 221 in water is demonstrated. Furthermore, characterization of the DRP was preformed with streptavidin-coated microbeads, and the measured response is in close agreement with the model. Finally, the use of DRP for measurement of dried cell mass and accurate cell counting is demonstrated with a detection limit of 1.46 ng.