A Noninvasive Vein Finder Based on a Tuned Microwave Loop Resonator

In this work, a noninvasive vein finder based on a tuned microwave loop resonator has been demonstrated to locate the vein in a cost-effective, reliable, and convenient way, addressing the challenges in venipuncture, especially in cases of difficult venous access. The sensor is a tuned loop resonator with a radius of 4.7 mm, incorporating a self-tuning pad and operating at 3.25 GHz with a reflection coefficient of $-$58 dB. It provides localized high-intensity electric fields that penetrate into tissues with sufficient depths. The sensor is based on the detection of electromagnetic resonant frequency shift that is susceptible to the distinctive dielectric properties of blood vessels inside the skin. The extensive simulations and experimental measurements on male and female subjects validate its effectiveness with consistent and distinguishable resonant frequency shifts. The sensor's stability across different forearm locations, its ability to differentiate between arteries and veins, and its adherence to safety regulations with low-power microwave signals contribute to its robustness. It shows great promise for improving venipuncture procedures, reducing complications, and enhancing patient comfort in a low-cost and noninvasive way.