A subnanowatt microbubble pressure sensor based on electrochemical impedance transduction in a flexible all-Parylene package

We present the first all-Parylene microbubble pressure transducer (μBPT) harnessing the ability of a microbubble (μB) to respond instantaneously to external pressure variations. A μB is electrolytically generated and physically trapped within a Parylene microchamber such that pressure-induced bubble size variation is detected by electrochemical impedance (EI) measurement. Real-time hydrostatic pressure measurement (-11.8 O/psi, ±0.1 psi) of negative and positive pressures (-2 - 4psi) is demonstrated. The open-package device design leverages the ambient liquid environment obviating the need for hermetic packaging techniques. μBPTs are biocompatible, flexible, ultra-miniature (200 μm diameter, 10 μm thick), and can be operated at very low power (≤ nW) making them especially attractive for wet, in vivo pressure measurement.