Phononic bandgap crystals
Phononic bandgap crystals, for classical elastic wave localization, are composite structures created through the N-dimensional (N = 1, 2, 3, 4, for up to three physical dimensions and one time dimension) periodic or aperiodic arrangement of inclusion media within a host medium of contrasting characteristic acoustic impedance. The solution of the elastic wave equation within unbounded Phononic bandgap crystals results in an elastic band structure with characteristic bands of frequencies where traveling waves are permitted, ranges of frequencies referred to as the phononic bandgap where all polarizations of elastic waves are exponentially attenuated, and frequencies corresponding to Phononic Bandgap edges where standing waves may be permitted. The phononic band structure is the mechanical analog of the photonic and electronic crystal band structure.
We study the theory, design methodology and experiments of electrostatically actuated Phononic bandgap crystal architectures (Fig. 1). Electrostatic actuation mitigates the use of piezoelectric transducers and provides action at a distance type forces so Phononic bandgap crystal edges may be free standing for potentially reduced anchor loss. Experimental characterization is performed in the frequency and spatial domains utilizing a high frequency laser-Doppler vibrometer. Frequency domain measurements yield the vibration spectrum at a single point on the surface of the device Phononic bandgap crystal (Fig. 2). Spatial domain measurements yield the vibration amplitude versus position on the surface of the Phononic bandgap crystal (Fig. 3).
We investigate and develop the applicability of our Phononic bandgap crystal architectures to physical sensors, signal processing elements, the improvement of micro-electromechanical systems (MEMS) and scalability to nano-electromechanical systems (NEMS).