Ultra-Sensitive Radio Frequency Biosensor at an Exceptional Point of Degeneracy Induced by Time Modulation

Abstract

We exploit the premises of exceptional points of degeneracy (EPDs) induced in linear time-periodic (LTP) systems to achieve extremely sensitive biosensors. The EPD is formed in a single LC resonator where the total capacitance is comprised of a time-varying capacitor in parallel to a biosensing capacitor. We use the time-periodic variation of a system parameter (e.g., capacitance) to achieve a second order EPD aiming at improving the sensitivity of liquid based radio frequency biosensors, leading to an intrinsic ultra sensitivity. We show the emergence of EPDs in such a system and the ultra sensitivity of the degenerate resonance frequency to perturbations compared to conventional RF sensors. Moreover, we investigate the capacitance and conductance variations of an interdigitated biosensing capacitor to the changes in the concentration of a biological material under test (MUT), leading to subsequent large changes in the resonance frequency of the LTP-LC resonator. A comparison with a standard LC resonator demonstrates the ultra-high sensitivity of the proposed LTP-LC based biosensor. In addition, we show the scalability of the biosensor sensitivity across different frequency ranges.