Mesoporous polymeric aerogels with high compressibility and durability have attracted great attention due to their environmentally sustainable applications. However, it is still challenging to develop polymeric aerogels in a simple, low-cost and mass produced way. Herein, we report a strategy to prepare a high porosity polymeric nanofibrous aerogel (referred to as NFA) by direct freeze-drying of the poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous suspension. It is noteworthy that this process is free of gelation and any solvent exchange. In addition, the PVA-co-PE nanofibers were mass-produced from our production line, based on a high throughput Melt-Extrusion-Phase-Separation technique. Additionally, the network of the NFA aerogels can be tuned by the host–guest assembly of the nanofibers and the foreign PVA nano-lamellae from disordered/ordered cellular to a leaf-like structure. Further modification of the NFA by gaseous methyltrichlorosilane (MTS) led to covalently bonded siloxane nanoparticles formed on the surface, thereby facilely realizing the nanofibrous aerogel from hydrophilic to hydrophobic as well as achieving excellent resilience. The corresponding hydrophobic aerogel (designated as HNFA) possessed a slightly larger density of 11.1 mg cm⁻³ with an almost unchanged porosity of 99% and meso–macroporous pores of 5–100 nm compared with the NFA (8.3 mg cm⁻³). They are demonstrated as good thermal insulators (0.033–0.044 W m⁻¹ K⁻¹), high-performance air filters (99.2% filtration efficiency with 64 Pa pressure drop), organic pollutants absorbers (2500–5329% weight gain) and continuous water/oil separators. Therefore, this study opens up a new approach for simple and large-scale preparation of polymeric aerogels for versatile applications.

Flexible pressure sensors have attracted tremendous research interests due to their wide applications in wearable electronics and smart robots. The easy-to-obtain fabrication and stable signal output are meaningful for the practical application of flexible pressure sensors. The graphene/polyurethane foam composites are prepared to develop a convenient method for piezo-resistive devices with simple structure and outstanding sensing performance. Graphene oxide was prepared through the modified Hummers method. Polyurethane foam was kept to soak in the obtained graphene oxide aqueous solution and then dried. After that, reduced graphene oxide/polyurethane composite foam has been fabricated under air phase reduction by hydrazine hydrate vapor. The chemical components and micro morphologies of the prepared samples have been observed by using FT-IR and scanning electron microscopy (SEM). The results predicted that the graphene is tightly adhered to the bare surface of the pores. The pressure sensing performance has been also evaluated by measuring the sensitivity, durability, and response time. The results indicate that the value of sensitivity under the range of 0–6 kPa and 6–25 kPa are 0.17 kPa⁻¹ and 0.005 kPa⁻¹, respectively. Cycling stability test has been performed 30 times under three varying pressures. The signal output just exhibits slight fluctuations, which represents the good cycling stability of the pressure sensor. At the same stage, the response time of loading and unloading of 20 g weight turned out to be about 300 ms. These consequences showed the superiority of graphene/polyurethane composite foam while applied in piezo-resistive devices including wide sensitive pressure range, high sensitivity, outstanding durability, and fast response.

Flexible wearable pressure sensors have received extensive attention in recent years because of the promising application potentials in health management, humanoid robots, and human machine interfaces. Among the many sensory performances, the high sensitivity is an essential requirement for the practical use of flexible sensors. Therefore, numerous research studies are devoted to improving the sensitivity of the flexible pressure sensors. The fiber assemblies are recognized as an ideal substrate for a highly sensitive piezoresistive sensor because its three-dimensional porous structure can be easily compressed and can provide high interconnection possibilities of the conductive component. Moreover, it is expected to achieve high sensitivity by raising the porosity of the fiber assemblies. In this paper, the three-dimensional reduced graphene oxide/polyolefin elastomer (RGO/POE) nanofiber composite aerogels were prepared by chemical reducing the graphene oxide (GO)/POE nanofiber composite aerogels, which were obtained by freeze drying the mixture of the GO aqueous solution and the POE nanofiber suspension. It was found that the volumetric shrinkage of thermoplastic POE nanofibers during the reduction process enhanced the compression mechanical strength of the composite aerogel, while decreasing its sensitivity. Therefore, the composite aerogels with varying POE nanofiber usage were prepared to balance the sensitivity and working pressure range. The results indicated that the composite aerogel with POE nanofiber/RGO proportion of 3:3 was the optimal sample, which exhibits high sensitivity (ca. 223 kPa⁻¹) and working pressure ranging from 0 to 17.7 kPa. In addition, the composite aerogel showed strong stability when it is either compressed with different frequencies or reversibly compressed and released 5000 times.