Non-invasive Flexible Electromagnetic Sensor for Potassium Level Monitoring in Sweat

In this paper, a novel wearable and non-invasive potassium sensors based on a flexible electromagnetic filter is presented. The filter topology includes a tapered feed line loaded four supershaped double split ring resonators with gap parallel to the line. The Kapton dielectric substrates was taken into account for its flexibility, chemical and high temperature resistance, high threshold for wear and abrasion. The embedded resonators have a reduced footprint and they was designed in order to exhibit enhanced sensitivity close to the operating frequency of 3 GHz. Moreover, a parametric analysis was carried out with the aim to identify the shape and geometrical parameters ensuring the optimal sensing capabilities. A prototype of the designed flexible sensor was realized and preliminary laboratory tests was carried out by considering a collagen sensing layer. The obtained results highlight a lowering of the resonance peak as the potassium concentration increases.