Self-sensing multicore fiber probe for interferometric measurement of lateral displacement and force

Tactile probes for small forces are of key importance for various research fields such as micro-assembly or micro coordinate measuring, robotics or minimally-invasive surgery. The present study investigates the potential for the realization of a multicore fiber (MCF) based, high-resolution lateral displacement and force sensor. The sensor itself is very simple in design, consisting only of a single piece of multicore fiber with cleaved/polished end faces, mounted in a cantilever configuration. The fiber segment interferometry (FSI) principle allows to measure the strain along the separate cores of the sensor fiber. From the differential strain measured within opposing core pairs, it is possible to infer the lateral displacement of the fiber tip. To characterize the sensor performance, a setup originally designed for metrological stiffness calibration of atomic force microscope (AFM) cantilevers was used. This allowed the comparison with external interferometric reference measurements, as well as the characterization of the sensor stiffness necessary for force sensing. These investigations were carried out for three sensor shaft lengths of 5 mm, 10 mm and 15 mm. The results show that noise levels below 1 n m / H z for tip displacement and 1 n N / H z for force sensing at the fiber tip at a 5 kHz bandwidth are possible with this simple and widely applicable concept. • Self-sensing multicore fiber piece serves as both deformation body and sensor. • Universally applicable concept for compact, cost effective, disposable tactile probe. • Measurement of lateral displacement or force with noise levels in the nm or nN range.