Asymmetrically coupled resonators for mass sensing

S. Marquez, M. Alvarez, J.A. Plaza, L.G. Villanueva, C. Dominguez and L.M Lechuga

Appl. Phys. Lett., 111, 2017, 113101-113104 - DOI: 10.1063/1.5003023

Abstract: Mechanically coupled resonators have been applied in the last years to the development of nanomechanical masssensors
based on the detection of the different vibration modes of the system by measuring on a single resonator. Their
sensitivity and capability for detecting multiple analytes strongly depends on the design and coupling strength between
the mechanically coupled resonators in an array format. We present a theoretical and experimental study of the
behavior of an asymmetrically coupled array of four different resonators. These doubly clamped beam resonators are
elastically coupled by an overhang region of varying length along the transversal axis of the array. The results show that
parameters such as the gap between microbeams and the overhang length affect the coupling strength, tuning the
system from highly disordered and highly localized (weak coupling) to highly delocalized (strong coupling). In the strong
coupling and partially‐localized case, the distances between resonant peaks are larger, reaching higher eigenfrequency
values. In this case, relative changes in a specific eigenstate, due to an added mass, can be markedly large due to the
energy distribution over a single microbeam. A strong coupling also facilitates performing the detection on the relative
frequency shift mode which can usually be resolved with better precision than the amplitude changes.

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