Department of Mechanical Engineering
Title: "Capacitive Micromachined Ultrasonic Transducer (CMUT) for Chemical Detection in Air"
Research Adviser: Prof. B. T. Khuri-Yakub
Date: Wednesday, Dec. 8th, 2010
Time: 2:00 pm
Location: Packard 202
Abstract:
Miniaturized chemical and biological sensor systems have a wide range of emerging applications for consumer, military, and medical use. Portable sensors with high sensitivity and reliability can replace the bulky equipment, expanding the potential applications beyond the conventional use of in-laboratory detection.
This dissertation describes the resonant chemical sensor platform based on capacitive micromachined ultrasonic transducers (CMUTs). A CMUT is composed of 100s of flexural-mode resonators connected in parallel. The device is chemically activated by inkjet coating of functionalization polymer layers with a thickness of ~50 nm. Five-channel CMUT chemical sensor presents good sensitivity to commonly used solvents. Analyte identification is also successfully performed based on the multi-channel chemical sensor.
This dissertation also presents ppt-level detection of dimethyl methylphosphonate (DMMP), a common simulant used in detector calibrations for sarin gas (GB), using an optimized CMUT design with a mass sensitivity of 4.8 ag/Hz. A low-noise oscillator using the CMUT exhibits an Allan deviation of 0.2 Hz. With a 50-nm thick proprietary polymer layer (Sandia National Laboratory), the sensor shows an excellent volume sensitivity of 21 pptv/Hz. Based on the system noise floor, a calculated mass resolution is 33 zg/um2 (3σ) and a limit of detection level of DMMP is 12.6 pptv (3σ). In addition, the sensor shows good selectivity to DMMP.
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Kwan-Kyu Park
Ph.D Candidate
E. L. Ginzton Laboratory,
Center for Nanoscale Science and Engineering
345 Via Peublo
Stanford University
Stanford, CA 94305
Tel: 650-353-1376
email: kwankyup@stanford.edu
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