Design of microstrip patch sensor for non-invasive body electrolyte monitoring

Abstract

Diagnostic of Human sweat is becoming a gold standard for non-invasive procedure to identify electrolyte levels. In this paper a low cost, non-invasive microstrip patch antenna-based sensor is proposed to detect human electrolyte level from sweat. The designed sensor is a Copper patch antenna with operating frequency of 0.5 GHz to 3.5 GHz. The antenna is designed on 1.5 mm thick paper-based substrate. For sensitivity comparison, three different dielectric constants ranging from 1.0 to 2.0 have been tested in designed antenna structure having resonant frequency of 1.575 GHz. The dielectric properties of substrate are transmuted when liquid is absorbed by it. The variation of magnitude of reflection coefficient and shift in resonant frequency is observed for various concentrations of sodium chloride (NaCl) ranging from 50 mmol/L to 300 mmol/L. First resonance is considered for data analyzing, as there is significant change in both resonance frequency and magnitude of reflection coefficients for different level of electrolytes. Paper substrate with higher dielectric constant shows better sensitivity compared to lower one.