Fully Wireless, In Vivo Assessment of Superimposed Physiological Vital Signs Using a Biodegradable Passive Tag Interrogated with a Wearable Reader Patch

Abstract

State‐of‐the‐art biosignal monitoring systems strive to achieve a balance between biocompatibility, biodegradability, and miniaturized, unobtrusive signal acquisition, thus requiring further research for improved user safety, mobility, and comfort. Here, a fully wireless sensing system is presented for real‐time in vivo assessment of physiological vital signs, addressing these challenges to enhance performance and user experience. The system features a biodegradable passive tag with a nanoscale crack‐based strain gauge sensor connected to a coil antenna on a gelatin‐ionic liquid substrate (GIS). The thermal crosslinking in the GIS promotes adhesion, while the presence of ionic liquid decreases the self‐resonance frequency of the BCA to below 100 MHz, enabling the device to operate in detuned mode. A lightweight (1.547 g) wearable reader patch interrogates an implanted passive tag via near‐field inductive coupling and transmits sensory data to peripheral devices via Bluetooth. Thus, the system ensures minimal tissue absorption and extended transmission range while consuming ≈80 mW of power during operation. In vitro and in vivo studies, culminating in successful implementation within a rat model, validated the implanted tag's biocompatibility and the system's capability to wirelessly acquire and process superimposed physiological vital signs, highlighting its potential to enhance patient outcomes through improved diagnostic and monitoring practices.