Robust microhoneycomb-like nanofibrous aerogels derived from cellulose and lignin as highly efficient, low-resistant and anti-clogging air filters

Highly Elastic Spongelike Hydrogels for Impedance-Based Multimodal Sensing

Hydrogel-based sensors have been widely studied for perceiving the environment. However, the simplest type of resistive sensors still lacks sensitivity to localized strain and other extractable data. Enhancing their sensitivity and expanding their functionality to perceive multiple stimuli simultaneously are highly beneficial yet require optimal material design and proper testing methods. Herein, we report a highly elastic, sponge-like hydrogel and its derived multimodal iontronic sensor. By unidirectional freeze casting of poly(vinyl alcohol) (PVA) with electrospun cellulose nanofibers (CNF), a hierarchical structure with aligned PVA channels supported by interlaced CNF tangles is created. The structure ensures both efficient mass transport and good elasticity, enhancing reversible compressibility and ionic conductivity. Combining this sponge hydrogel with impedance-based measurement methods allows the development of multimodal sensors capable of detecting local strain, position, and material type of object-in-contact. Integrating these sensing capabilities, a two-dimensional small motion monitor, a 3D input interface, and a material identification gripper are demonstrated. This study provides a simple approach to versatile multimodal sensors.

Nanoporous air filtering systems made from renewable sources: benefits and challenges

There is a crucial need for air purification systems due to increasing air contamination, while conventional air-filtering materials face challenges in eliminating gaseous and particulate pollutants. This review examines the development and characteristics of nanoporous polymeric materials developed from renewable resources, which have rapidly advanced in recent years. These materials offer more sustainable alternatives for nanoporous structures made out of conventional polymers and significantly impact the properties of porous polymers. The review explores nanoporous materials' production from renewable sources, filtering mechanisms, physicochemical makeup, and sensing capabilities. The recent advancements in this field aim to enhance production techniques, lower pressure drop, and improve adsorption efficiency. Currently, supporting approaches include using adsorbent layers and binders to immobilize nanoporous materials. Furthermore, the prospects and challenges of nanoporous materials obtained from renewable sources used for air purification are discussed.

Hydrophobic Silk Fibroin-Agarose Composite Aerogel Fibers with Elasticity for Thermal Insulation Applications

Aerogel fibers, characterized by their ultra-low density and ultra-low thermal conductivity, are an ideal candidate for personal thermal management as they hold the potential to effectively reduce the energy consumption of room heating and significantly contribute to energy conservation. However, most aerogel fibers have weak mechanical properties or require complex manufacturing processes. In this study, simple continuous silk fibroin-agarose composite aerogel fibers (SCAFs) were prepared by mixing agarose with silk fibroin through wet spinning and rapid gelation, followed by solvent replacement and supercritical carbon dioxide treatment. Among them, the rapid gelation of the SCAFs was achieved using agarose physical methods with heat-reversible gel properties, simplifying the preparation process. Hydrophobic silk fibroin-agarose composite aerogel fibers (HSCAFs) were prepared using a simple chemical vapor deposition (CVD) method. After CVD, the HSCAFs' gel skeletons were uniformly coated with a silica layer containing methyl groups, endowing them with outstanding radial elasticity. Moreover, the HSCAFs exhibited low density (≤0.153 g/cm3), a large specific surface area (≥254.0 m2/g), high porosity (91.1-94.7%), and excellent hydrophobicity (a water contact angle of 136.8°). More importantly, they showed excellent thermal insulation performance in low-temperature (-60 °C) or high-temperature (140 °C) environments. The designed HSCAFs may provide a new approach for the preparation of high-performance aerogel fibers for personal thermal management.

Recent Progress in Modification Strategies of Nanocellulose-Based Aerogels for Oil Absorption Application

Oil spills and oily wastewater have become a major environmental problem in recent years, directly impacting the environment and biodiversity. Several techniques have been developed to solve this problem, including biological degradation, chemicals, controlled burning, physical absorption and membrane separation. Recently, biopolymeric aerogels have been proposed as a green solution for this problem, and they possess superior selective oil absorption capacity compared with other approaches. Several modification strategies have been applied to nanocellulose-based aerogel to enhance its poor hydrophobicity, increase its oil absorption capacity, improve its selectivity of oils and make it a compressible and elastic magnetically responsive aerogel, which will ease its recovery after use. This review presents an introduction to nanocellulose-based aerogel and its fabrication approaches. Different applications of nanocellulose aerogel in environmental, medical and industrial fields are presented. Different strategies for the modification of nanocellulose-based aerogel are critically discussed in this review, presenting the most recent works in terms of enhancing the aerogel performance in oil absorption in addition to the potential of these materials in near future.