Flexible strain sensors based on carbon nanotubes/polydimethylsiloxane composites with a segregated structure prepared by sustainable emulsion method

Abstract

Flexible strain sensors have been widely used in many fields because of their excellent adaptability and flexibility. Nonetheless, creating these sensors through simple methods that achieve a low percolation threshold and high sensitivity continues to pose a challenge. In this paper, a segregated structure was realized in a carbon nanotube/polydimethylsiloxane (CNT/PDMS-S) strain sensor by a sustainable emulsion method that involved the mixing cellulose nanocrystals (CNCs), CNTs, PDMS and water. The incorporation of CNC improved the stability of CNTs in aqueous suspension. Consequently, The CNT@CNC nanocomposites were strategically placed in the gaps between the PDMS microspheres, creating a segregated structure. The segregated structure notably lowered the percolation threshold of the composite to 0.49 wt%. Moreover, we found that the CNT/PDMS-S sensor containing 1.5 wt% CNTs showed excellent sensing performance, which not only had a wide strain measurement range and could adapt to the strain change from 0% to 70%, but also had high sensitivity with a gauge factor (GF) of 290 at 70% strain. Meanwhile, the sensor had an excellent linear response (R2 ≥ 0.96) and can monitor the minimum strain of 0.1%. The proposed sensor demonstrated excellent response when applied to sense wrist movement, facial movement and closure, and syllable recognition. Highlights: Strain sensors with a segregated structure were realized by a sustainable method. The segregated structure greatly reduces the percolation threshold of sensor. The sensor has a high sensitivity, linearity, and wide strain detection range. The sensor features high resolution for tiny deformations sensing.