Fabrication of styrene–butadienestyrene (SBS) matrix-based flexible strain sensors with brittle cellulose nanocrystal (CNC)/carbon black (CB) segregated networks

•A styrene–butadienestyrene (SBS)/cellulose nanocrystal (CNC)/carbon black (CB) composite-based flexible strain sensor was designed through a Pickering emulsion template method.•The segregated CNC/CB networks enhance the conductivity of the composites.•The CNC incorporation and defect construction in segregated networks are conducive to improving the sensitivity of the sensor. Strain sensors based on conductive polymer composites (CPCs) filled with carbon black (CB) are potential as wearable detection devices for mass production due to their low cost. However, it is still challenging to design sensors with low CB loading and the conductivity and sensitivity guaranteed. Herein, a Pickering emulsion template method was conducted to design the styrene–butadienestyrene (SBS) matrix-based strain sensors, in which a conducting structure of segregated cellulose nanocrystal (CNC)/carbon black (CB) networks was constructed, improving the conductivity and reducing the percolation threshold (φc) to ∼0.28 wt%. Besides, the CNC incorporation and defect construction in the networks greatly promote the sensitivity of the sensor, the maximum gauge factor (GF) determined is beyond 260 within the 200% strain. Moreover, the sensor can exhibit remarkable working durability and reproductivity. All these above favorable properties have empowered the strain sensor with superior applicability in detecting various human motions (finger bending, elbow bending, knee bending, neck rotation, cheek bulging, and swallowing).