NOISE-BASED HIGH RESOLUTION ULTRASOUND IMAGING USING MICROENGINEERED SURFACES AND TRANSDUCERS

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The objective of this research is to develop ultrasonic imaging methods using the ubiquitously available but rarely exploited broad band thermal-mechanical noise in electromechanical systems. The theoretical approach is based on Green's function retrieval from diffuse noise sources and deep sub-wavelength resolution imaging with evanescent waves on engineered propagation surfaces. Micromachined ultrasonic transducers are used to record thermal-mechanical noise and provide a tunable microscale engineered surface for evanescent waves, forming the experimental platform to achieve sub-wavelength resolution imaging. Optimal configurations for controlling evanescent wave velocity, hence the effective sub-wavelength resolution, will be investigated and implemented through microscale engineering. Effects of noise field characteristics on the wave excitation and detection, and imaging performance will be explored. Feasibility of high resolution ultrasonic imaging within the diffraction limit (F-number 0.1-0.5) will be demonstrated in the 3-10MHz range using micromachined arrays integrated with low noise electronics. The results would impact design and implementation of microsystems for bio-imaging and bio-microfluidics. This project will impact integrated low-power biomedical systems such as medical implants through imaging and monitoring mechanical properties down to the cellular level. Noise-based high-frequency ultrasonics using microscale engineered surfaces can provide a transformative tool for many imaging applications requiring high resolution at lower frequencies. The project involves science teachers from predominantly minority enrolled high schools to create modular curriculum materials in physics and provides opportunities for student site visits to university laboratories. It will also lead to modular curriculum materials for undergraduate classes, and an interdisciplinary component for graduate classes taught by the PIs.