Arrays of Electrostatically Coupled Micro Resonators

Dynamics of large arrays of micro- and nanoelectromechanical (MEMS/NEMS) coupled resonators have received significant research attention over the last two decades. Coupled resonators with nominally identical or slightly detuned frequencies yield a wider bandwidth when compared to a single vibrating element. Due to their intrinsic filtering feature and ability to increase bandwidth, arrays of weakly coupled resonators find applications in inertial sensing, radio-frequency devices and frequency-signature speech processing. Micro and nanoscale mechanical resonators offer significant advantages over their macroscopic counterparts, including their low mass, high mechanical quality factor, and compatibility with integrated electronics. The collective behavior of these nonlinear interacting cantilever arrays is remarkably sensitive to the slightest perturbation in the environment, which makes them an excellent candidate for ultra-sensitive sensors for chemical or biological analytes. More specifically, nonlinear, coupled M/NEMS resonating cantilever arrays have been shown to possess complex dynamics such as parametric resonances, intrinsically localized modes, abrupt transitions between standing wave patterns, and sensitivity to defects. Here we explore, both numerically and experimentally, the collective dynamics of large arrays of micro cantilevers interacting elastically and electrostatically, through flinging fields. Arrays of various geometries including interdigitated cantilevers of nominally identical and linearly varying length were fabricated using a silicon on insulator (SOI) wafer with a highly doped single crystal silicon device layer. The devices were driven electrically and inertially, using a piezoelectric transducer, under ambient and vacuum conditions. Using electrostatic actuation, interactions between interdigitated cantilevers took place through fringing electrostatic fields within the overlap region. The system exhibited several unique standing wave patterns, excited through the parametric resonance mechanism, and showed sensitivity to defects and external loading. We believe that these remarkable features of micro and nano scale arrays open new interesting opportunities for the practical implementation of coupled arrays for ultra-sensitive chemical, biological, and force sensors in the future.

Krylov, S. Lulinsky, B. R. Ilic, I. Schneider, “Collective Dynamics and Pattern Switching in an Array of Parametrically Excited Micro Cantilevers Interacting through Fringing Electrostatic Fields,” Applied Physics Letters, 105, 071909, 2014.

N. Dick, S. Grutzik, C. B. Wallin, B. R. Ilic, S. Krylov, A. T. Zehnder, “Actuation of Higher Harmonics in Large Arrays of Micromechanical Cantilevers for Expanded Resonant Peak Separation,” J. of Vibration and Acoustics, 140, pp. 051013-1 - 051013-10, 2018.