A Ring-Shaped MEMS-Based Piezoresistive Force Sensor for Cardiac Ablation Catheters

Catheter ablation, a minimally invasive surgical procedure that uses radiofrequency (RF), has simplified the treatment process of cardiac arrhythmias. The success of cardiac ablation procedures greatly depends on the effective lesion formation, which relies on the contact force between tissue and the tip. Thus, a real-time estimate of catheter tip contact force is essential during cardiac ablation procedures. We present the design, fabrication, and characterization of a piezoresistive Micro-Electro-Mechanical System (MEMS)-based force sensor for measuring catheter tip contact force in real-time. The sensor has four bridges with boron-doped piezoresistive elements for detecting the contact force. The sensor dimensions and the piezoresistors doping concentrations were optimized using finite element analysis. The sensor is designed to measure a catheter tip contact force between 0 – 0.8 N. An in-house indentation setup is developed and integrated with a commercial load cell to characterize the fabricated sensor. The sensor results showed a linearity of 99.5 %, maximum hysteresis of 5 %, and sensitivity of 108 ±
$11 \Omega $
/N. A customized catheter tip integrated with the fabricated force sensor was tested on excised porcine heart tissues to measure the catheter tip contact force.