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Crosslinked poly(vinyl alcohol) (PVA)/cellulose nanofibril (CNF) hybrid aerogel micro-spheres with two different particle sizes were fabricated via a combination of the water-in-oil (W/O) emulsification process and the freeze-drying process. The aerogel micro-spheres were highly porous with a bulk density as low as 0.0047 g/cm for the large microspheres. The pore size of the microspheres ranged from nano- to micro-meters. Preliminary biocompatibility assays of the aerogel microspheres were investigated with NIH 3T3 cells to explore their potential application as cell culture scaffolds. The highly crosslinked aerogel microspheres were robust and were able to maintain their shape during the cell culture process. The live/dead assay showed that the cells could be seeded, attached, and proliferated on the surface of PVA/CNF aerogel microspheres. The fluorescence images showed that some of the cells migrated into the inner pores of the microspheres. Moreover, the large microspheres with larger average pore sizes had a higher cell count than that of the small microspheres. This study confirms that the PVA/CNF aerogel microspheres fabricated in this work are nontoxic and biocompatible. Furthermore, the interconnected, highly porous nanofibrous structure of the microspheres can successfully facilitate cell attachment, differentiation, and proliferation. [ABSTRACT FROM AUTHOR]

Superhydrophobic and crosslinked poly(vinyl alcohol) (PVA)/cellulose nanofibril (CNF) aerogel microspheres were prepared via a combination of the water-in-oil (W/O) emulsification process with the freeze-drying process, followed by thermal chemical vapor deposition of methyltrichlorosilane. The oil phase and the cooling agent were judiciously selected to ensure that the frozen ice microspheres can be easily separated from the emulsion system. The silanized microspheres were highly porous with a bulk density ranging from 4.66 to 16.54 mg/cm 3 . The effects of the solution pH, stirring rate, and emulsifier concentration on the morphology and microstructure of the aerogel microspheres were studied. The highly porous structure of the ultralight aerogel microspheres demonstrated an ultrahigh crude oil absorption capacity (up to 116 times its own weight). This study provides a novel approach for the large-scale preparation of polymeric aerogel microspheres with well-controlled particle sizes that can be used for various applications including oil and chemical spill/leak clean-up. [ABSTRACT FROM AUTHOR]

• A novel strategy to build aerogel/foam hybrid structure was demonstrated via in situ unidirectional freeze-drying process. • A hybrid conductive filler system, CNT/GO dispersion system, was used to fabricate highly conductive carbon-based aerogel. • The PU foam acts as a structural scaffold providing resilient properties and mechanical durability to the composites. • The piezoresistive sensitivity of the composites could be simply modulated by selecting the initial pre-strain. [Display omitted] Carbon-based aerogels (CA) with durable piezoresistive properties possess great promise for applications in wearable electronics. However, it is still a great challenge to fabricate high performance aerogel sensors due to the limits of mechanical properties. We recently developed a novel strategy to build aerogel/foam hybrid structure that can effectively enhance the mechanical properties of aerogel-based sensors. Herein, CA/polyurethane foam (PUF) composite was fabricated via in situ unidirectional freeze-drying process starting from a carbon nanotubes (CNTs)/graphene oxide (GO) aqueous dispersion stabilized with chitosan (CS) which was filled into the porosity of an open cell PUF. The resulting composite shows a microscopic anisotropy in the CA with electrical conductivity as high as 10.54 S m−1. The piezoresistive sensitivity of the resulting composite can be simply modulated over a wide range from 1.1 to 3.6 by adequately selecting its initial pre -strain. The CA/PUF composite exhibits excellent compressible resilience at the strain of 50% for at least 100 cycles. In addition, the sensor was successfully applied for detecting various human motions. These unique properties make the realized composite a promising candidate for effective flexible piezoresistive strain sensors in wearable applications. [ABSTRACT FROM AUTHOR]

We present the polarization-dependent highly absorptive in Ka-band composition of conventional polyurethane foam filled with in situ synthesized aerogel coated by reduced graphene oxide (rGO). The rGO-based aerogel was in situ prepared into the open-cell polyurethane foam (PUF) skeleton through a bidirectional freeze-drying process. The aerogel is composed of the flat lamellas stacks, possessing the anisotropic structure and unique electromagnetic properties. Further improvement of the electromagnetic shielding ability was possible by the rGO coating introduction as a coupling layer between PUF and rGO-based aerogel. This enhances the overall conductivity of the resulting composites: 1.41 + 3.33i S/m vs. 0.9 + 2.45i S/m for PUF loaded with in situ synthesized aerogel without rGO coating.With this mechanically robust plane easy to process coating one could achieve −20 dB by power with the record light structure (0.0462 g/cm2). That could compete in view of the weight per cm2 even with graphene-based absorbers comprising either dielectric matching elements or back metal reflectors, or both. [ABSTRACT FROM AUTHOR]