Inductive Displacement Sensor of Novel Design Printed on Polyimide Foil

Displacement sensors play a key role in many applications. In this paper, an inductive structure is presented which changes its inductance with deformation, which serves as a measure of displacement. The structure itself is produced by ink-jet printing on a flexible polyimide foil, using a conductive silver-based nanoparticle ink. The foil is subsequently cut in such a way to allow for extending in a direction perpendicular to the foil plane. The resulting dependence of the inductance on the amount of extension is analyzed both in calculation and experimental measurement. Calculation is done using a variation of the Neumann formula adjusted to calculating self-inductance. A simple mathematical model of the structure deformation is introduced which proved to give results very close to the results obtained by measurement. The displacement range of the experimentally verified structure is up to 25 mm; however, the structure is expected to be scalable and therefore it should be possible to adapt it to various measurement ranges.