A Contactless Electrochemical Impedance Measurement Method

We present the first demonstration of a passive, contactless method to interrogate electrochemical impedance (EI) via a microfabricated MEMS coil. EI measurement was achieved using the principle of reflected impedance between a pair of inductively coupled coils. Ionic concentration and electrolyte temperature were wirelessly transduced from measurement electrodes connected to a microfabricated coil in a flexible thin film substrate. This technique is widely applicable for resistive transduction and obviates the need for soldering discrete electronic components, microcontrollers, batteries, and bulky hermetic packaging. It also features low power consumption (~75 μW) and all biocompatible construction (only Au, Ti, and Parylene C), making it ideal for use in harsh or in vivo environments.