Ultra-highly stretchable and anisotropic SEBS/F127 fiber films equipped with an adaptive deformable carbon nanotube layer for dual-mode strain sensing

Conductive elastomer composites are widely recognized as prospective strain sensing materials in soft robotics and biomedical engineering due to their high elasticity and light weight. However, achieving high-performance strain sensors with a broad sensing range and high gauge factor synchronously is still challenging due to the trade-off between sensitivity and stretchability. In this work, an anisotropic fiber film-based strain sensor with extraordinary dual-mode sensing capabilities was developed using highly aligned styrene-block-poly(ethylene-ran-butylene)-block-poly-styrene (SEBS)/PEO-PPO-PEO triblock copolymer (F127) fiber films as an anisotropic elastomer matrix and intimately incorporated multiwall carbon nanotubes (CNTs) as a deformable conductive coating. Via blending F127 with SEBS to endow the elastomer with superhydrophilicity, aligned electrospinning was subsequently employed to prepare highly stretchable and hydrophilic SEBS/F127 fiber films, followed by surface-induced assembly to obtain anisotropic CNT/SEBS/F127 composite fiber films equipped with an adaptive deformable CNT conducting layer. Attributed to the strong interfacial interaction between CNTs and the anisotropic fiber matrix, the obtained CNT/SEBS/F127 sensor exhibited excellent mechanical strength and exceptional dual-mode strain-sensing performance in terms of an ultra-broad response range (up to 1300% strain) and an ultra-high sensitivity (GF value of 3564 at 700% strain) when stretching parallel and perpendicular to the fiber alignment, respectively, as well as fast response/recover times (51 ms/71 ms in parallel, and 100 ms/100 ms in perpendicular) and great sensing stabilities (5000 stretching-releasing cycles) in both loading directions. Additionally, the CNT/SEBS/F127 strain sensor was able to detect various human motions, such as breathing, phonation and joint bending, presenting great potential in next-generation wearable electronics.