Smart Textiles with Polymer Optical Fibre Implementation for In-Situ Measurements of Compression and Bending

The objective of this paper is to study the ability to insert polymeric optical fibres (POFs) into a textile in order to measure and differentiate compression and bending as close as possible to the skin. The influence of each single elementary mechanical loading on the optical signal given by the POF was systematically studied. For this purpose, an optical device, including a light source, an optical sensor, and a photodiode, was used. The optical sensor consisted of two areas: a deformation sensitive area consisting of a PDMS POF and a non-deformation sensitive light transmission area consisting of PMMA multifilaments. The PMMA POF allowed for the transmission of light from the source to the PDMS POF and then to the photodiode while being flexible and deformable. In the first step, the sensor POF was individually characterized under four elementary loading conditions: tension, torsion, transverse compression, and pure bending. The light intensity variation during loading was measured to correlate light losses and strain, and then the sensitivity to the loading condition was determined. The POF was highly sensitive to bending, sensitive to compression, and insensitive to tension and torsion. Therefore, a strategy has been developed to insert the POF sensor with control of the POF path inside the textile structure. The POF integrated knitted structure was characterized under compression and bending conditions. The sensitivity obtained is effective as a smart textile for compression and bending measurements.