High-Q magnetoelastic oscillators via amorphous magnetic microwires for wireless liquid sensing

This study explores magnetoelastic resonance (MER) in FeSiB-based amorphous magnetic microwires (AMWs) optimized for operation in liquid media and the determination of their surrounding properties. The microwires, fabricated via the Taylor-Ulitovsky technique, were subjected to a comprehensive analysis to establish the optimal geometry and magnetic bias conditions required to maximize magnetomechanical coupling and resonance stability. This optimization resulted in well-defined resonance modes in the 125–230 kHz range, depending on the microwire length. A major focus was placed on ensuring high reproducibility and long-term stability in aqueous environments; this was achieved by implementing a controlled surface oxidation process specifically targeting the microwire ends to stabilize the resonant baseline. Despite the inherent damping effects of the liquid phase, stable and high-resolution tracking of the resonance frequency was maintained. The proposed device has been extensively studied and tested by analyzing how its resonance frequency and amplitude evolve in water-glycerol mixtures. By correlating the system's response with the medium's density and viscosity, we demonstrate that it effectively tracks hydrodynamic loading effects. Finally, a high-Q oscillator based on amorphous magnetic microwires achieved a quality factor exceeding 17,000 in liquid media. This exceptional stability allows for high-resolution monitoring with a limit of detection as fine as 0.08% for 60% v/v mixtures, establishing a robust foundation for miniaturized, cost-effective, and non-contact sensors optimized for high-sensitivity trace detection. This system enables high-accuracy biofluid rheology monitoring, offering significant potential for early-stage disease diagnostics, environmental sensing, and advanced biosensing applications.