Subnanowatt Microbubble Pressure Transducer

We present the first all-Parylene microbubble pressure transducer (μBPT). The μBPT utilizes an electrolytically generated microbubble (μB), trapped in a Parylene microchamber, for pressure sensing. Pressure-induced bubble size variation is detected by electrochemical impedance measurement. Real-time hydrostatic pressure measurement with excellent sensitivity (-10.7 Ω/psi, ±0.1 psi) up to 1.8 psi and tracking of internal pump pressure in a MEMS-based implantable drug delivery system were achieved. The transduction method and device format uniquely leverage the surrounding liquid environment, obviating the need for hermetic or special packaging techniques for sensing in wet environments. Arrayed μBPTs are biocompatible, fabricated on flexible substrates, ultra-miniature (200 μm diameter, 10 μm thick), and can be operated at very low power ( ≤ nW) making them especially attractive for in vivo pressure measurement applications