A Robust Uniaxial Force Sensor for Minimally Invasive Surgery

Abstract

This paper presents a novel, miniature uniaxial force sensor for use within a beating heart during mitral valve annuloplasty. The sensor measures 5.5 mm in diameter and 12 mm in length, and provides a hollow core to pass instrumentation. A soft elastomer flexure design maintains a waterproof seal. Fiber optic transduction eliminates electrical circuitry within the heart, and acetal components minimize ultrasound imaging artifacts. Calibration uses a nonlinear, viscoelastic method, and in vitro tests demonstrate a 0 to 4 N force range with RMS errors of 0.13 N (<3.2%). In vivo tests provide the first endocardial measurements of tissue-MIS instrument interaction forces in a beating heart.