Ultrasound is routinely used for safely imaging unborn babies deep in the body and diagnosing a variety of illnesses from liver to heart diseases. This opens the possibility that it can also be used to power medical implants such as cardiac pacemakers and neural stimulators. Capacitive devices, like microphones, are widely used for sound to electrical signal conversion but they are deemed unsuitable for implants as they require batteries to charge them. In this research, parametric effect, like a child pumping a swing by periodically standing and squatting to increase the size of the swing's oscillations, is investigated to remove this limitation. It turns out that one move a plate of a capacitor using sound waves or mechanical input over a certain threshold level to start this type of oscillation in an electrical circuit without a need for a battery. Initial analysis shows that this energy conversion can be very efficient, leading to remotely powering medical devices with ultrasound, and this oscillation can be started potentially with very small input levels, leading to very sensitive mechanical sensors to be used for energy harvesting, seismic or underwater sensing. In this project, these possibilities and fundamental limits of this unique approach will be explored experimentally and through detailed models.
The objective of this research is to test a radically different approach to acoustic power transfer and sensing through the use of electrical parametric oscillators (resonators) driven by acoustic waves. In addition to optimized power transfer efficiency, the parametric amplification and noise squeezing for acoustic sensing applications will be explored by analyzing the fundamental mathematical problem of coupled oscillator based parametric systems and parametric super-resonance. Both analytical and numerical analysis methods will be utilized. This project will generate the proof of concept data for demonstration of efficient power transfer and model verification to develop new type of devices through ultrasound experiments in 500kHz-2MHz range. Use of inductance and resistance modulation for parametric resonance will be explored. If successful, this project, by exploiting nonlinearity and resonance, can lead to a paradigm shift in acoustic transduction which heretofore depended predominantly on linear, passive properties of capacitive and piezoelectric devices.
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.
