Polyvinyl alcohol/starch modified cotton thread surface as a novel colorimetric glucose sensor

•Polyvinyl alcohol (PVA)/starch composite was modified on cotton thread surface.•This modification could improve entrapment capacity and stability of reagents.•The modified thread was applied as a distance-based colorimetric glucose sensor.•Glucose concentration is directly proportional to the color length of the complex.•Human tear (25 µL) was tested on the sensor for screening diabetes within 120 s.