Design and electrochemical preparation of inductive copper coils for magnetic particles detection

New devices based on inductive planar coils have been designed in a manner that they can be used for the detection of magnetic particles in biodetection applications from the changes induced in coil inductance mounted in simple resonance differential filter circuit configurations. By simulating the conditions needed to achieve minimum electrical resistance and maximum sensibility, the planar coil design has been developed. The number of tracks and aspect ratio has been optimized for different theoretical track thicknesses. Using the optimized mask, electrodeposition was used to prepare coils of around 15-μm thick, with good edge definition and low electrical resistance, matching with the optimum simulated values. The resonant frequency of the fabricated coils measured using an impedance analyzer is identical for each coil type. Preliminary tests of the sensing ability of the coils were performed, revealing a change in the resonant frequency when a magnetic powder is present over the coil.