Microwave sensing technique based label-free and real-time planar glucose analyzer fabricated on FR4

In this paper, we have demonstrated a real-time label-free microwave analyzer fabricated on FR4 board for quantitative analysis of the glucose concentration. In this, sensing area configured of interdigital (IDT) structures is embedded in the centre of coplanar waveguide (CPW) transmission line. Here, centre of the IDT structures is acting as sensing area, where analyte under test (AUT) is confined by integrating a Poly-DiMethyl-Siloxane (PDMS) cavity on to the IDT structures. Analyte's inherent electrical property that is dielectric constant is used as source of quantitative analysis when electromagnetic (EM) waves interact with AUT. The glucose concentration dependent dielectric constant causes shift in RF parameters which are investigated in the form of S-parameters, peak frequency, impedance, resistance and reactance. These parametric measurements are carried out using Vector Network Analyzer (VNA) and the variation in each parameter w.r.t the glucose concentration ranging from 0 g/mL to 1 g/mL, are closely observed. A rigorous study has been carried out for multidimensional characterization where measured sensitivity in terms of S11 magnitude is 15.30 dB/g/mL, S11 peak frequency is 235.32 MHz/g/mL, S12 magnitude is 5 dB/g/mL, S12 peak frequency is 168 MHz/g/mL, resistance is 10.91 Ω/g/mL, reactance is 23.82 Ω/g/mL, and impedance is 63.11 Ω/g/mL with linear regression coefficient always better that 0.87. Experimental results show that proposed planar analyzer has a great potential to determine glucose multidimensional quantitative analysis for high accuracy and with improved sensitivity.