Observation of localised vibration modes in a micromechanical oscillator trio with coupling overhang for highly sensitive mass sensing

The use of vibration mode localisation in arrays of micromechanically coupled, nearly identical beam-shaped resonators, has been studied for ultra-sensitive mass detection and analyte identification. Eigenstate shifts (amplitude change in this work) that are three to four times (compared to a single resonator), and orders (compared to a resonator array) of magnitude greater than corresponding shifts in resonant frequency for an induced mass perturbation are theoretically analysed, as well as considering the geometry of the coupling overhang. A mechanically coupled beam-shaped 3-resonator array was therefore analysed, fabricated and characterised. The experimental results show that bigger amplitude change could be obtained for the two outermost resonators owing to the symmetrical design, which are found to correspond well to the analytical results.