A Shear Sensing Pad, Based on Ferrofluidic Actuation in a Microstructured Optical Fiber

We demonstrate a compact, flexible, and high dynamic range optical fiber shear sensor, based on the fusion of microstructured optical fibers and magnetofluidic technologies. A microstructured optical fiber Bragg grating is infiltrated with ferrofluid and embedded, together with a miniature magnet, in a polydimethylsiloxane block, constituting a “soft” shear stress sensing pad. Repeatable shear stress displacements of this flexible pad from 100 μm to 4.25 mm were monitored, in one and two dimensions, and left and right directions, while corresponding to shear forces between 0.42 and 3.86 N. The presented sensing unit operates well under the application of vertical pressure of 11 kPa. Shear sensing results are presented and analyzed demonstrating the envelope of operation of this flexible sensing pad.