Could an implantable sensor both monitor lung flow and generate power?

The rise of Smart Health has led to implantable healthcare devices that can diagnose and monitor diseases in real-time. Some diagnoses are based on fluids in the body, like asthma. A key challenge of current implantables is that they are difficult to power and require surgeries to replace batteries. We show that a piezoelectric flow sensor could monitor a fluid flow and simultaneously power itself from that flow. The effectiveness of this sensor/harvester depends on flow properties. It therefore demands advanced models that capture tradeoffs between sensing fidelity and harvesting potential. To develop these models, we built a platform for testing the sensing/harvesting capability of piezocantilevers in airflows modeled after human breathing. We found that oscillating voltage on the piezocantilever can both charge a capacitor and map to the amplitude and frequency of the breath. We explored how well models can predict harvesting and sensing potential based on breath type. These models open up a broad range of applications that we are exploring, including a smart stent that alerts patients to obtrusions or dislodging. How these models scale with flow speed/direction, turbulence intensity, and cantilever size offer design ideas for sensing/harvesting in other bodily channels.