Detection of Polystyrene Beads Concentration Using an SOI-MEMS Differential Rotational Thermal Piezoresistive Resonator for Future Label-Free Biosensing Applications

This work shows a differential rotational thermal piezoresistive resonator (DR-TPR) design, fabrication, and characterization. The resonator uses silicon on insulator (SOI) microelectromechanical systems (SOI MEMS) technology. The sensing of carboxyl-polystyrene beads requires estimating the variation in the frequency of the resonator. It can serve as an alternative enabling technology to detect small molecules having wide implementations in clinical and industrial applications. The resonator uses a negative frequency shift to find the change in the mass due to the chemical absorption of the carboxyl-polystyrene beads on the DR-TPR surface. The method of using DR-TPR can attain label-free detection for many future biomarkers. The use of carboxyl-polystyrene beads to showcase the potential of DR-TPR as a mass sensor for future chemical/biosensing applications is the highlight of the paper. It includes the characterization in different concentrations of immobilization on the resonator surface. The work shows the operation of the resonator in an ionic buffer solution which is crucial for its future applications. The Q value of 80 with differential feedthrough cancellation is measured in phosphate-buffered saline (PBS) using DR-TPR.