Covalently Interconnected Thermoplastic Polymeric Nanofiber/Carbon Nanotube Composite Nanofibrous Aerogels for Piezoresistive Sensors

With the development of wearable devices, the demand for pressure sensing has prompted the development of flexible pressure sensors with excellent overall performance, especially flexible piezoresistive sensors with long-term durability. In this study, covalently interconnected poly(vinyl alcohol-co-ethylene) (EVOH)/MWCNTs composite nanofibrous aerogels with typical "layer–pillar" hierarchical porous structure were prepared by hydroxyl aldehyde condensation to cross-link thermoplastic nanofibers and hydroxylated carbon nanotube. Benefiting from the porous structure of composite nanofibrous aerogels and robust bonding between EVOH and MWCNTs, the prepared composite nanofibrous aerogel exhibited an ultralow density (18.27 mg/cm3), excellent compressibility and restorability (up to 80% strain), and remarkable fatigue durability exceeding 1000 times. Meanwhile, the compressive strength of the cross-linked composite aerogel was increased by a factor of 3.5 compared to the un-cross-linked composite aerogel (9.70 kPa). The composite nanofibrous aerogel can be assembled as a piezoresistive sensor, with a sensing capacity up to 80% strain (corresponding to 33.49 kPa) and detection limit of 80 Pa. Furthermore, the dynamic strain sensitivity and pressure sensitivity of the piezoresistive sensor are GF = 1.51 and S = 0.28 kPa–1, respectively. More importantly, the cyclic stability of the pressure resistance sensor was outstanding; even after 3000 cycles, its curve remained essentially consistent with the initial 50 cycles. These successes ensure the excellent performance of EVOH/MWCNTs composite nanofibrous aerogels for sensitive monitoring of mechanical signals, such as body posture monitoring, and show the great potential of aerogel sensors as the next generation of wearable electronics.