Fabrication of electrically conductive poly(styrene-b-ethylene-ran-butylene-b-styrene)/multi-walled carbon nanotubes composite fiber and its application in ultra-stretchable strain sensor

•Ultra-stretchable SEBS/ MWCNTs composite fiber was fabricated through wet spinning.•Effects of MWCNTs content and L/D ratio on the mechanical, electrical and electromechanical properties of the composite fiber were investigated.•The composite fiber showed a strain sensing range of up to 0–506%.•The composite fiber was formed into a knitted fabric and had the ability of detecting human motions.