NEMS-based sensing using a vibrating or oscillating NEMS resonator can be patterned on a silicon-on-insulator (SOI) wafer, e.g., using electron beam lithography, metal deposition, lift-off techniques, and various etching techniques, and are operated in flexural modes using optical and/or capacitive techniques. By actuating the NEMS sensor harmonically at or near its fundament resonant frequency, small frequency shifts can be detected with a high degree of sensitivity. Hence, as analyte molecules or a single molecule attach to the functionalized layer on the surface of the device , frequency shifts can be measured that provide indicia of the nature and concentration of the analyte molecules.
In this size regime, NEMS provides relatively high fundamental resonant frequencies, very small active masses, relatively low intrinsic energy dissipation, a relatively high intrinsic quality (Q-) factor, very small heat capacities, and so forth. In combination, these attributes can provide unprecedented sensitivities at relatively high operating frequencies with a potential for a wide range of sensing, actuating, and signal processing applications.
With resonant Atomic Force Microscopy (AFM), the very same problem makes AFM imaging and force measurements in water quite challenging. For example, in AFM, a vibrating micro-cantilever can be used to detect small nanoscale forces from the surface for mapping the surface topography. However, in water, the force sensitivity, and hence, the signal-to-noise ratio decreases because the Q-factor of the cantilever decreases, e.g., to about 10. Accordingly, a variety of advanced probe microscopy techniques, such as AFM and magnetic resonance force microscopy (MRFM), will benefit immensely from the development of micro-cantilever sensor probes with increased Q-factor for use in water.