Nonplanar Wireless Differential Microsensor for Integration on Intravenous Catheters for Therapeutic Drug Monitoring and Other Applications

This paper reports a nonplanar passive wireless differential microsensor integrated with intravenous (IV) catheters of small diameters to facilitate in situ real-time monitoring of concentrations of drugs or other target molecules/biomarkers in the bloodstream. The sensor is based on magnetoelastic (ME) transduction with passive wireless interrogation to detect target molecules as mass loading using a functionalized coating. It uses a differential configuration to distinguish the mass loading effect from variations caused by changes in surrounding fluid medium. The sensor was curved to match the catheter form factor with maximized active sensor surface area, packaged in housing with embedded microfluidic features for sample filtration/pretreatment, and integrated on an 18-gauge catheter with 1.3 mm outer diameter for demonstration. Preliminary experimental results validated functions of curved ME sensors with degraded performance due to curving fully restored by an optimized annealing process, demonstrating 5.3 Hz/ng mass sensitivity and proper differential operation with the medium effect eliminated.