A Deployable Multifunctional Sensor for a Catheter Device for the Renal Denervation of Resistant Hypertension

This study developed a deployable multimodal and multifunctional sensor for a catheter device for renal denervation (RDN) procedures to treat resistant hypertension. The catheter device has three deployable spines. When the device is deployed, it can be used to perform ablation of the renal nerve, detect the contact force exerted by the device on the renal artery wall, measure the temperature of the ablation sites, and provide feedback to control the ablation power. Each spine comprises a microelectromechanical system (MEMS) multimodal sensor chip, contact force sensor, 100- $\mu \text{m}$ -thick tungsten foil for radiopacity, and shape memory alloy spine. The MEMS chip has a platinum-based resistance temperature detector (Pt RTD) integrated with a radio frequency (RF)-powered heating electrode. It can withstand 32 ablation cycles with an RF generator setting of 8 W for 60 s per ablation cycle. An ex vivo ablation study demonstrated that an RF power range of 1–1.5 W achieved optimal ablation lesions. The Pt RTD or temperature sensor has a sensing range of 25 °C–94 °C and sensing response time of <0.5 s. The contact force sensor has a sensing range of 50–500 mN, with a minimum resolution of 50 mN and hysteresis error of 0.7 $\text{k}\Omega $ . In benchtop studies, the force sensor performed well during catheter deployment under three conditions: in air, in a hollow tube, and in saline solution. During catheter activation, the force sensor can detect the contact force between the tube wall and force-sensor module. The force-sensor resistance readout is consistent for both the hollow tube and saline solution.