A Batch-Patterned Self-Expanding Biliary Stent with Conformal Magnetic PDMS Layer and Topologically-Matched Wireless Magnetoelastic Sensor

This paper presents a system for wirelessly monitoring the accumulation of sludge within biliary stents. The system comprises a sensor and biasing permanent magnet layer that conform to the meshed topology and tubular curvature of a biliary stent. The sensors have an active area of 7.5 mm × 29 mm and a mass of 9.1 mg. Annealing the sensor at 375°C results in reducing the required biasing magnetic field from 6 Oe to 2 Oe. The integrated system shows a 38% decrease in resonant frequency (from 61.6 kHz to 38.2 kHz) after an applied mass load of 20.9 mg, or 2.3× the mass of the sensor. The system architecture allows the mechanical properties of the stent to be maintained while adding important monitoring capabilities to the implanted device.