Abstract—This paper demonstrates a flexible magnetic-induction carotid patch for noninvasive carotid pulse monitoring and stenosis-phantom discrimination. The proposed patch integrates a flexible spiral coil, resonant readout circuit, and medical-tape interface, forming an LC resonant tank that converts carotid-induced electromagnetic coupling variations into resonant frequency modulation. The resonant operating frequency was set to 5.4 MHz through phantom-based frequency tuning to enhance pulse sensitivity. In ECG-synchronized human measurement, the proposed patch detected carotid pulse rhythms with a heart rate mean absolute error of 1.76 bpm and a Pearson correlation coefficient of r=0.747 compared with ECG. Silicone-based carotid bifurcation phantoms representing 0 %, 50 %, and 70 % stenosis were further evaluated under identical pump settings. The extracted pulsatile frequency variation Δf decreased with increasing stenosis level, enabling discrimination among normal, moderate, and severe stenosis phantom conditions. To our best knowledge, this work is the first proof-of-concept demonstration of applying magnetic-induction resonant frequency sensing to a flexible carotid patch for stenosis-level phantom discrimination.

Index Terms— Carotid stenosis; Eddy current sensor; Magnetic induction; Patch sensor; Resonant frequency; wearable device