No-core PDMS fiber for large-scale strain and concentration measurement

•A no-core PDMS fiber with character of high tensile properties, good optical transmittance and high transparency.•A new pigtail by heat shrinkable tube.•A maximum strain sensitivity of 3.5070 /ε with a large scale strain from 0% to 40%.•Concentration sensitivity of 1.3354 /% was experimentally demonstrated. Stretchable strain sensors are urgently needed in measurement field. This paper reports a no-core polydimethylsiloxane (PDMS) optical sensor, which is suitable for large scale strain and concentration measurement with high sensitivity. The proposed no-core PDMS fiber is composed of polydimethylsiloxane and curing agent in a certain propotion. The output spectrum loss of the no-core PDMS fiber varies with stretching or surrounding changes. Experimental results show that the highest strain sensitivity is 3.5070 /ε in the range from 0% to 25%. Also, intensity change of the output spectrum is linear with brine concentrations from 2.5% to 10%. The proposed no-core PDMS fiber has the potential to be used in some fields such as wearable devices, structure health in composite materials, civil structures, and concentration measurement.