Noninvasive Glucose Sensor Based on Parity-Time Symmetry

We discuss a noninvasive technique to detect glucose changes with enhanced sensitivity based on paritytime (PT) symmetry. We detect glucose level changes within the skin by measuring the frequency shift in the electromagnetic resonance induced within a PT-symmetric system that sandwiches the tissue sample under analysis. Even though the sample itself is lossy, and therefore, resonances would be damped, the introduction of balanced gain and loss enables an efficient sensing mechanism that bypasses the conventional limitations of passive sensing schemes. Our results indicate that the resonance shift can be made fairly linear with respect to the glucose concentration variations, and the expected accuracy is large. We also investigate a realistic system to implement the noninvasive PT-symmetric glucose sensor using loop antennas and negative impedance converters, exploring its sensitivity with respect to design errors and disorder.