Textile Multitouch Force-Sensor Array Based on Circular and Non-Circular Polymer Optical Fibers

A 3 × 3 textile integrated force-sensor array is presented that is based on the cross coupling of optical fibers and provides multi-touch capability. The force sensing relies on cross coupling between two fibers that are aligned orthogonally to each other. The actual coupling is improved by an increased contact area and higher scattering at the fiber crossing. A systematic analysis of different parameters is done for the driving and the sensing fiber, which involves materials, size, fabrication parameters as well as the cross-section shape. The results reveal that the combination of a rather stiff driving fiber and a flexible sensing fiber from elastomer (TPU) lead to the highest sensitivities in the range of 45.5 pW/N. The application of non-circular cross sections can improve the coupling efficiency by directing the side-emitted light better towards the sensing fiber. A trilobal-shaped driving fiber lead to an increase of 5 dBs, whereas the shaping of the sensing fiber improved the efficiency by another 7.5 dB.