Coplanar Hybridization of Half-Mode Magnetic Plasmonic Skyrmions: Realization and Application in a Flexible Wearable Microwave Sweat Metasensor

In this article, a novel flexible and compact microwave metasensor using coplanar hybridization of half-mode plasmonic skyrmions (HMPSs) is proposed for continuous wearable sweat monitoring. The magnetic HMPSs are successfully observed in the microwave domain by designing an ultrathin complementary concentrically interconnected semi-ring (CCISR) metastructure. This metastructure offers several attractive features, such as compactness, multimode operation, and topological robustness. Furthermore, the coplanar hybridization of magnetic HMPSs is innovatively realized by establishing a mirror-symmetric CCISR metastructure. This design induces each half-mode magnetic skyrmion pair to split into a pair of hybridized bonding and anti-bonding modes, significantly increasing the number of operating modes within a limited frequency range. Building on these unique features, a flexible metasensor integrated with a functional sweat-collection layer is proposed for wearable sweat sensing. The real-time variations in sweat volume and rate can be dynamically tracked by observing shifts in resonant frequencies across various modes of the metasensor. Moreover, a resonance feature integration method (RFIM) is developed to provide a robust and highly sensitive framework for processing the multimode responses of the metasensor. To validate the performance of the metasensor in sweat sample monitoring, a prototype is fabricated and tested. Experimental results demonstrate the effectiveness of the metasensor in continuously monitoring sweat rate and volume across a wide dynamic range from 0 to $300~\mu $ L. The results also highlight its high sensitivity and robustness. These advantages position the proposed metasensor as a promising solution for wearable sweat monitoring.