Wireless Measurement of the Degradation Rates of Thin Film Bioresorbable Metals Using Reflected Impedance

Abstract

A method using reflected impedance to determine the electrical degradation rates of bioresorbable metals for physically transient electronic devices is outlined. This approach uses known mutual inductor interactions with simple single turn disk coil geometries and a frequency measurement system to track the reduction of the mean thickness of a thin film metal ring as it degrades. Experiments using <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {500~ \text {n} \text {m} }$ </tex-math></inline-formula> thick zinc rings, fabricated by photolithography, thermal evaporation and lift-off, found a mean degradation rate of 278 nm h−1 in 37 °C de-ionised water. Experiments in 37 °C 1 mM hydrochloric acid found two distinct periods of degradation and a total degradation rate of 632 nm h−1 that closely matched the degradation rate measured using profilometry of 608 nm h−1.