(Georgia Institute of Technology, 2008-10-21)
Brand, Oliver
The presentation gives an introduction to resonant microsensors providing a frequency output signal. These sensors generally benefit from an excellent frequency resolution, which is ideally limited only by the length of the counting period and the short-term frequency stability of the microstructure's resonance frequency. Device-level and system-level approaches to generate a measurand-dependent frequency signal are discussed and concepts to improve Q-factor, short-term frequency stability and ultimately sensor resolution are highlighted. Furthermore, the presentation discusses frequency drift challenges and introduces methods for drift compensation. The above concepts and approaches are illustrated using two resonant microsensor examples: (i) a mass-sensitive microsensor platform for gas- and liquid-phase chemical sensing based on disktype silicon microstructures and (ii) a cantilever-based resonant magnetic microsensor with a resolution suitable for Earth field applications.
(Georgia Institute of Technology, 2008-10-10)
Brand, Oliver
A resonant microsensor platform based on disk-type microstructures vibrating in an in-plane resonance mode for chemical and biochemical sensing applications in gas and liquid environments is presented. Based on measured short-term frequency stabilities of 1.1 10^-8 in air and 2.3 10^-6 in water, mass detection limits in the low femtogram and sub-picogram, respectively, are achieved. In a biosensing application, biomolecules are immobilized on the resonator surface. Upon selective binding of analyte molecules (e.g. via antibody-antigen binding), the mass of the resonator is increased, resulting in a measurable decrease of its resonance frequency. The feasibility of liquid-phase biosensing using the disk resonators is demonstrated experimentally by detecting anti-beta-galactosidase antibody using covalently immobilized beta-galactosidase enzyme.