Cross-Sensitivity of a Dual-Port Potentiometric Sensor based on Auto-Tuning RFID ICs

Skin monitoring devices, like Ultra-High-Frequency (UHF) Radio Frequency Identification (RFID) Epidermal sensors, can improve Point of Care (PoC) testing, with benefits such as faster and more accurate diagnoses, improved patient outcomes, and increased convenience. Since a comprehensive screening of the user/patient may require the simultaneous acquisition of multiple parameters, the cohabitation of several wireless sensors in a small space will be highly likely in the near future. This will, however, force proximity of the antennas and their Integrated Circuits (ICs), leading to coupling interactions, that are typical of multi-sensing systems. This paper introduces a model that evaluates the cross-sensitivity, i.e., the mutual interference, of a system of two RFID-coupled sensors, preliminarily evaluated off-skin. The model specifically involves a peculiar class of RFID ICs equipped with auto-tuning technology that offered up new sensing opportunities in recent years. The mathematical relationships governing the coupling phenomenon are derived and then numerically implemented for different coupling arrangements. Our promising results, corroborated by experimental evaluations, reveal that configurations with very low cross-sensitivity can be achieved, suggesting the feasibility of designing a device capable of simultaneously monitoring multiple potentiometric parameters without any interference between close ICs.