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

Abstract

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/cm 3 ), 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.

Bioinspired Low Hysteresis Flexible Pressure Sensor Using Nanocomposites of Multiwalled Carbon Nanotubes, Silicone Rubber, and Carbon Nanofiber for Human–Computer Interaction

“…In recent years, there has been significant progress in the field of flexible electronics, driven by a growing demand across diverse industrial sectors. This has spurred a focused and heightened interest in the development of flexible sensors customized for temperature, , pressure, , strain, , humidity, , gas, , monitoring applications, and other fields. Among them, flexible pressure sensors have been widely studied due to their good application prospects in the field of electronic skin (e-skin), , wearable electronics, , intelligent robotics, , human body movement monitoring, , and human–computer interaction. , Depending on the sensing principle and output signal, flexible pressure sensors can be classified as piezoresistive, , capacitive, , piezoelectric, , and friction electric. , Within this category of sensors, the principle of a flexible piezoresistive sensor is to convert an external mechanical pressure stimulus applied to the device into a recordable change in resistance signal, which consists of the contact resistance at the interface between the electrode and the sensing material and the internal resistance of the sensing material and the electrode. , The material’s resistance can be expressed by the following formula: R = ρ L / S , where R is the resistance of the material, ρ is the resistivity, L is the length, and S is the cross-sectional area. , Flexible piezoresistive sensors have garnered widespread attention and thorough examination owing to their inherent advantages, notably low manufacturing costs and uncomplicated structures.…”