pNUTs: Piezoelectric Nanoscale Ultrasonic Transducers for Dust-Like Airborne Communication Links

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AbstractUnsolicited Proposal 2104142“pNUTs: Piezoelectric Nanoscale Ultrasonic Transducers for Dust-Like Airborne Communication Links”Ultrasound has found a broad range of applications spanning from underwater communication, nondestructive evaluation of structural components, and fingerprint sensing, to haptics feedback, ranging, real-time locating systems and analog computing. The ultrasonic transducer is the core component behind an ultrasound system. Its wide deployment for a new realm of applications was made possible by the miniaturization of the transducer using micromachined thin films. Further miniaturization of the films forming the transducer to the nanoscale could yield substantial improvements in device sensitivity or dramatic reduction in area, hence enabling a new set of far reaching applications such as communication amongst networks of extremely small form factor (“dust-like”) sensors or microrobots and non-intrusive biomedical or neural implants. However, further miniaturization comes with fundamental challenges associated with the synthesis of the films, the control of residual stresses in the structure, and the electromechanical design of the transducer. This project plans to tackle these fundamental scaling challenges and deliver a new class of devices labeled as piezoelectric nanoscale ultrasonic transducers (pNUTs). To minimize propagation losses, pNUTs operate at frequencies between 40 kHz and 100 kHz. Operation in this frequency range of nanoscale transducers is challenged by the high sensitivity to residual stresses and interactions with air, which tend to stiffen the structure and make it extremely hard to precisely set the device resonant frequency. Given these constraints, the research efforts are focused on synthesizing nanoscale piezoelectric films of aluminum nitride (as thin as 10 nm) with controllable stress and arranging them in a novel pNUT geometry. pNUTs arrays are also investigated in order to achieve orders of magnitude improvement in sensitivity for a given form factor. The field use of pNUTs is going to be demonstrated through board-level implementation of airborne communication links for wake-up receivers. These demonstrations will inform the researchers on the ultimate sensitivity, range and modulation speed that pNUTs are capable of. "This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.