Research Summaries

Back Scanning Laser Vibrometer for MEMS Sound Sensor Characterization

Fiscal Year 2018
Division Graduate School of Engineering & Applied Science
Department Physics
Investigator(s) Karunasiri, Gamani
Sponsor Office of Naval Research (Navy)
Summary Our group at the Naval Postgraduate School (NPS) has been conducting research on bio-inspired micro-electro-mechanical system (MEMS) directional sound sensors based on Ormia Ochracea fly’s hearing system. Ormia Ochracea is a parasitic fly that has evolved the ability to accurately locate a particular cricket chirp for the purpose of laying eggs in the cricket. Unlike humans, the fly has two eardrums physically connected by a cartilaginous bridge and can be modeled as a coupled mechanical oscillator with two resonant modes. The cricket chirps produce a sound with wavelength of almost two orders of magnitude larger than the eardrum separation of the fly. The fly appears to analyze the superposition of the two resonant oscillation modes to determine the incident direction of the cricket chirp, thus allowing for accurate localization of crickets. A typical MEMS directional sound sensor consists of two wings connected in the middle by a bridge to mimic the fly’s hearing system. The entire structure is connected to the substrate by two torsional legs at the center. The sensors that we are currently exploring found to have directional resolution approaching to that of the fly. As the research expands to different operation environments and specific applications, it is necessary to enhance our characterization capabilities to aid the development of these new sensors. Laser Doppler Vibrometry is a widely accepted tool for dynamic characterization of MEMS structures. Using automated scan capability, the proposed scanning laser vibrometer system can measure structural resonance and display deflections with amplitudes down to the picometer level and frequencies up to 1 MHz. The acquisition of the proposed system will greatly expand our capabilities of nondestructive monitoring of inner workings of the MEMS sensors in microscale resolution, which will aid in fine-tuning of the design programs as well as fabrication processes. The proposed vibrometer system will directly support the current research programs sponsored by ONR, NPS-ONR (NRP) and NPS-ONR (CRUSER). In addition to aiding the research programs, instrument will be highly valuable for characterization of MEMS structures that the students fabricate during the two MEMS classes that we teach in the Graduate School of Engineering and Applied Sciences.
Keywords Characterization Laser MEMS Scanning Sensor Sound Vibrometer
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Data Publications, theses (not shown) and data repositories will be added to the portal record when information is available in FAIRS and brought back to the portal