Multifunctional polyether block amides/carbon nanostructures piezoresistive foams with largely linear range, enhanced and humidity-regulated microwave shielding

[Display omitted] •The highly porous and multifunctional elastomer foam was prepared via ScCO2 blowing.•PEBA/CNS composites were foamed successfully above melt temperature of PEBA.•The foams exhibited enhanced and humidity-regulated EMI shielding.•The sensor had a large linear range up to 70% strain, long lifetime and good repeatability.•The foams had great prospects in monitoring human motion and health protection. Flexible foam sensors have great potential applications in wearable electronic skin and motion detection. However, they usually have a low linear range, complex and no environment-friendly preparation process. Meanwhile, the obtaining of highly porous foam sensors also faces challenge via supercritical foaming. Herein, a novel, environment-friendly and easily scaled-up batch melt foaming technology was utilized to fabricate flexible, highly porous and multifunctional polyether block amides (PEBA)/carbon nanostructures (CNS) composite foams. The foams showed good piezoresistive performance with largely linear range as well as enhanced and humidity-regulated electromagnetic interference (EMI) shielding. PEBA/CNS composites were foamed successfully above the melt temperature of PEBA, and the foamed PEBA/CNS composite exhibited refined cell morphology and broadened foaming window. The highly porous (0.76) PEBA/CNS composite foams had a largely linear range up to 70 % compression strain with a gauge factor (GF) of 1.24, which also exhibited durable, highly invertible and reproducible piezoresistive behavior. Meanwhile, the PEBA/CNS composite foams were capable of monitoring human motions as wearable sensors. In addition, the specific EMI SE of PEBA/CNS composite foams was sharply increased. Furthermore, EMI shielding of PEBA/CNS composite foams could be adjusted between inefficient shielding (20 dB) with the change of humidity. Such foams had a great prospect in monitoring human motions while also protecting health from electromagnetic waves as a wearable device.