Compliant Glass Mechanism Instrumented with a Bragg Grating to Measure Indentation Force

This paper presents a force sensor made of a compliant glass mechanism instrumented with a waveguide and a Bragg grating, measuring the reflected wavelength shift produced by the strain in the compliant element generated by the applied force. The compliant element geometry and material have been chosen for the sensor to be spliced or manufactured at the extremity of an optical fiber, enabling possible insertion of the instrument in the bronchial tree after embedding in a proper catheter. The context of this research is the mechanical discrimination between healthy and cancerous lung tissues based on their mechanical signature. The paper proposes a comprehensive study including the mechanical design of the structure and the optimization of the production parameters, thanks to an experimental parametric study. After experimental characterization of the mechanism stiffness, the optical response to a mechanical force is reproduced with two different samples on two different days (more than 25 repetitions). The conclusion is that a fair linear and repeatable response is observed (±26 mN) for forces ranging from 0 to 250 mN.