3D Printing of Ultralow-Concentration 2D Nanomaterial Inks for Multifunctional Architectures.

The direct 3D printing of ultralight architectures with ultralow-concentration 2D nanomaterial inks is necessary yet challenging. Here, we describe an emulsion-based ink for direct printing using 2D nanomaterials, i.e., MXene and graphene oxide (GO). The electrostatic interactions between the ligands in the oil phase and the 2D nanomaterials in the aqueous phase help form sheet-like surfactants at the interface. The interactions between the anchored ligands among different droplets dictate the rheological characteristics of inks, enabling a gel-like behavior ideally suitable for 3D printing at ultralow concentrations of 2D nanomaterials. The 3D printed foams possess lightweight structures with densities of 2.8 mg cm-3 (GO-based) and 4.1 mg cm-3 (MXene-based), and the latter integrates outstanding electrical conductivity, electromagnetic shielding performance, and thermal insulation comparable to air. This work describes a general approach for direct-printing ultralight porous structures that take advantage of the inherent properties of 2D building blocks.

Multisource solid waste development of low-carbon ultra-light foamed insulation materials: A feasibility study.

The continuous increase in building energy consumption, and the increasing types and quantities of solid waste have seriously hindered the rapid development of social economy. Therefore, reducing building energy consumption while realizing the recycling of waste has become the mainstream topic of environmental protection construction in the new era. An alkali-activated ultra-light foamed insulation material (AFIM) for building walls was prepared using EPS particles as lightweight aggregates. The effects of EPS dosage, particle size, and gradation on the compressive strength, dry density, thermal conductivity, and volumetric water absorption of AFIM were studied. The results showed that while ensuring good mechanical properties of AFIM, EPS particles can significantly reduce the dry density, thermal conductivity, and volumetric water absorption of AFIM. Excitingly, the optimal thermal conductivity and dry density of AFIM were 0.0408 W/(m·K) and 127.03 kg/m3, respectively. The microscopic morphology results showed that there was good compatibility between EPS particles and AFIM slurry, and the interface transition zone (ITZ) between them was dense and without obvious cracks. In addition, the feasibility of AFIM was evaluated from four aspects: performance, energy consumption, carbon emissions, and life cycle cost (LCC). It was encouraged that the performance of AFIM was comparable to that of traditional insulation materials, and showed significant advantages in energy conservation, emission reduction and economic benefits compared to traditional insulatin materials.

Giant Negative Thermal Expansion in Ultralight NaB(CN)4.

Negative thermal expansion (NTE) is crucial for controlling the thermomechanical properties of functional materials, albeit being relatively rare. This study reports a giant NTE (αV ∼-9.2 ⋅ 10-5  K-1 , 100-200 K; αV ∼-3.7 ⋅ 10-5  K-1 , 200-650 K) observed in NaB(CN)4 , showcasing interesting ultralight properties. A comprehensive investigation involving synchrotron X-ray diffraction, Raman spectroscopy, and first-principles calculations has been conducted to explore the thermal expansion mechanism. The findings indicate that the low-frequency phonon modes play a primary role in NTE, and non-rigid vibration modes with most negative Grüneisen parameters are the key contributing factor to the giant NTE observed in NaB(CN)4 . This work presents a new material with giant NTE and ultralight mass density, providing insights for the understanding and design of novel NTE materials.

Direct Ink Writing of Pickering Emulsions Generates Ultralight Conducting Polymer Foams with Hierarchical Structure and Multifunctionality.

Porous materials with multiple hierarchy levels can be useful as lightweight engineering structures, biomedical implants, flexible functional devices, and thermal insulators. Numerous routes have integrated bottom-up and top-down approaches for the generation of engineering materials with lightweight nature, complex structures, and excellent mechanical properties. It nonetheless remains challenging to generate ultralight porous materials with hierarchical architectures and multi-functionality. Here, the combined strategy based on Pickering emulsions and additive manufacturing leads to the development of ultralight conducting polymer foams with hierarchical pores and multifunctional performance. Direct writing of the emulsified inks consisting of the nano-oxidant-hydrated vanadium pentoxide nanowires-generated free-standing scaffolds, which are stabilized by the interfacial organization of the nanowires into network structures. The following in situ oxidative polymerization transforms the nano-oxidant scaffolds into foams consisting of a typical conducting polymer-polyaniline. The lightweight polyaniline foams featured by hierarchical pores and high surface areas show excellent performances in the applications of supercapacitor electrodes, planar micro-supercapacitors, and gas sensors. This emerging technology demonstrates the great potential of a combination of additive manufacturing with complex fluids for the generation of functional solids with lightweight nature and adjustable structure-function relationships.

Ultralight and Superelastic Curly Micro/Nanofibrous Aerogels by Direct Electrospinning Enable High-Performance Warmth Retention.

Extremely low temperature has posed huge burden on the public safety concerns and global economics, thereby calling for high-performance warmth retention materials to resist harsh environment. However, most present fibrous warmth retention materials are limited by their large fiber diameter and simple stacking structure, leading to heavy weight, weak mechanical property, and limited thermal insulation performance. Herein, an ultralight and mechanically robust polystyrene/polyurethane fibrous aerogel by direct electrospinning for warmth retention is reported. Manipulation of charge density and phase separation of charged jet allows for the direct assembly of fibrous aerogels consisting of interweaved curly wrinkled micro/nanofibers. The resultant curly wrinkled micro/nanofibrous aerogel possesses low density of 6.8 mg cm-3 and nearly full recovery from 1500-cycle deformations, exhibiting both ultralight feature and superelastic property. The aerogel also shows low thermal conductivity of 24.5 mW m-1  K-1 , making synthetic warmth retention materials superior to down feather possible. This work may shed light on developing versatile 3D micro/nanofibrous materials for environmental, biological, and energy applications.

Ultralight type I transvaginal mesh: an alternative for recurrent severe posterior vaginal prolapse.

OBJECTIVE: This study aimed to analyze the medium-term outcomes of ultralight type I mesh for postmenopausal women with recurrent severe posterior vaginal prolapse (PVP). METHODS: All participants underwent transvaginal ultralight type I mesh repair between April 2016 and April 2021 and were followed until May 2022. Pelvic Organ Prolapse Quantification System (POP-Q) staging, mesh-related complications, Patient Global Impression of Improvement (PGI-I) scale and quality of life questionnaire responses were evaluated. The primary outcome was composite surgical success rate at the last follow-up, composite success being defined as no vaginal bulge symptoms, no POP-Q point at or beyond the hymen and no re-treatment for POP. Secondary outcomes included anatomic outcomes (POP-Q score), symptomatic relief and complications. RESULTS: The median follow-up was 37.3 months. At the last follow-up, the composite success rate was 75%, and POP-Q scores for the vault and posterior wall and quality of life questionnaire scores were significantly improved (p < 0.01). The subjective satisfaction (PGI-I ≤ 2) rate was 83.3%. There were no mesh-related complications. CONCLUSIONS: Ultralight mesh can achieve good clinical outcomes and substantially improve the quality of life of patients with severe recurrent PVP in the medium term, and may thus be a viable alternative for treating this condition.

Gold Aerogel Monoliths with Tunable Ultralow Densities.

Herein we report the fabrication of ultralight gold aerogel monoliths with tunable densities and pore structures. Gold nanowires are prepared at the gram scale by substrate-assisted growth with uniform size, ultrathin diameters, high purity, and a high aspect ratio. Freeze-casting of suspensions of these nanowires produces free-standing, monolithic aerogels with tunable densities from 6 to 23 mg/cm3, which to the best of our knowledge represents the lowest density monolithic gold material. We also demonstrate that the pore geometries created during freeze-casting can be systematically tuned across multiple length scales by the selection of different solvents and excipients in the feedstock suspension. The mechanical behavior of porous materials depends on relative density and pore architectures.

Ultralight Electrolyte for High-Energy Lithium-Sulfur Pouch Cells.

The high weight fraction of the electrolyte in lithium-sulfur (Li-S) full cell is the primary reason its specific energy is much below expectations. Thus far, it is still a challenge to reduce the electrolyte volume of Li-S batteries owing to their high cathode porosity and electrolyte depletion from the Li metal anode. Herein, we propose an ultralight electrolyte (0.83 g mL-1 ) by introducing a weakly-coordinating and Li-compatible monoether, which greatly reduces the weight fraction of electrolyte within the whole cell and also enables Li-S pouch cell functionality under lean-electrolyte conditions. Compared to Li-S batteries using conventional counterparts (≈1.2 g mL-1 ), the Li-S pouch cells equipped with our ultralight electrolyte could achieve an ultralow electrolyte weight/capacity ratio (E/C) of 2.2 g Ah-1 and realize a 19.2 % improvement in specific energy (from 329.9 to 393.4 Wh kg-1 ) under E/S=3.0 µL mg-1 . Moreover, more than 20 % improvement in specific energy could be achieved using our ultralight electrolyte at various E/S ratios.

Macroscopic Ultralight Aerogel Monoliths of Imine-based Covalent Organic Frameworks.

The use of covalent organic frameworks (COFs) in practical applications demands shaping them into macroscopic objects, which remains challenging. Herein, we report a simple three-step method to produce COF aerogels, based on sol-gel transition, solvent-exchange, and supercritical CO2 drying, in which 2D imine-based COF sheets link together to form hierarchical porous structures. The resultant COF aerogel monoliths have extremely low densities (ca. 0.02 g cm-3 ), high porosity (total porosity values of ca. 99 %), and mechanically behave as elastic materials under a moderate strain (<25-35 %) but become plastic under greater strain. Moreover, these COF aerogels maintain the micro- and meso-porosity of their constituent COFs, and show excellent absorption capacity (e.g. toluene uptake: 32 g g-1 ), with high removal efficiency (ca. 99 %). The same three-step method can be used to create functional composites of these COF aerogels with nanomaterials.

Fatal gyroplane crash.

Gyroplanes are mainly used for sports aviation. Experience is required when flying these special aircraft because in 40% of gyroplane crashes, the passengers do not survive. Herein, a fatal gyroplane crash of a tandem-seat gyroplane with two occupants is reported. The occupants, both 49-year-old males, fell from a height of approximately 20 m to 30 m. In both cases, the cause of death was polytrauma with typical findings of deceleration trauma. The pilot, who probably lost his helmet in the crash, had a ring fracture at the base of his skull. As there is not much literature on autopsy findings in the case of light aircraft crashes, these autopsy findings are presented and discussed.

Ultralight Conductive Silver Nanowire Aerogels.

Low-density metal foams have many potential applications in electronics, energy storage, catalytic supports, fuel cells, sensors, and medical devices. Here, we report a new method for fabricating ultralight, conductive silver aerogel monoliths with predictable densities using silver nanowires. Silver nanowire building blocks were prepared by polyol synthesis and purified by selective precipitation. Silver aerogels were produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to weld the nanowire junctions. As-prepared silver aerogels have unique anisotropic microporous structures, with density precisely controlled by the nanowire concentration, down to 4.8 mg/cm3 and an electrical conductivity up to 51 000 S/m. Mechanical studies show that silver nanowire aerogels exhibit "elastic stiffening" behavior with a Young's modulus up to 16 800 Pa.

Self-Expansion Construction of Ultralight Carbon Nanotube Aerogels with a 3D and Hierarchical Cellular Structure.

A novel and simple strategy is developed to construct ultralight and 3D pure carbon nanotube (CNT) aerogels by the spontaneous expansion of superaligned CNT films soaked in a piranha (mixed H2 SO4 and H2 O2 ) solution, followed by cryodesiccation. The macroscopic CNT aerogels have an extremely low apparent density (0.12 mg cm-3 ), ultrahigh porosity (99.95%), high specific surface area (298 m2 g-1 ), and a hierarchical cellular structure with giant and ultrathin CNT sheets as cell walls. The pure CNT aerogels show high adsorption abilities for various kinds of solvents, and have great potential in widespread applications such as energy storage, catalysis, and bioengineering.

Ultralight Interconnected Metal Oxide Nanotube Networks.

Record-breaking ultralow density aluminum oxide structures are prepared using a novel templating technique. The alumina structures are unique in that they are comprised by highly aligned and interconnected nanotubes yielding anisotropic behavior. Large-scale network structures with complex form-factors can easily be made using this technique. The application of the low density networks as humidity sensing materials as well as thermal insulation is demonstrated.

Ultralight mesoporous magnetic frameworks by interfacial assembly of Prussian blue nanocubes.

A facile approach for the synthesis of ultralight iron oxide hierarchical structures with tailorable macro- and mesoporosity is reported. This method entails the growth of porous Prussian blue (PB) single crystals on the surface of a polyurethane sponge, followed by in situ thermal conversion of PB crystals into three-dimensional mesoporous iron oxide (3DMI) architectures. Compared to previously reported ultralight materials, the 3DMI architectures possess hierarchical macro- and mesoporous frameworks with multiple advantageous features, including high surface area (ca. 117 m(2) g(-1)) and ultralow density (6-11 mg cm(-3)). Furthermore, they can be synthesized on a kilogram scale. More importantly, these 3DMI structures exhibit superparamagnetism and tunable hydrophilicity/hydrophobicity, thus allowing for efficient multiphase interfacial adsorption and fast multiphase catalysis.

Direct Synthesis of Polyimide Curly Nanofibrous Aerogels for High-Performance Thermal Insulation Under Extreme Temperature.

Maintaining human body temperature is one of the basic needs for living, which requires high-performance thermal insulation materials to prevent heat exchange with external environment. However, the most widely used fibrous thermal insulation materials always suffer from the heavy weight, weak mechanical property, and moderate capacity to suppress heat transfer, resulting in limited personal cold and thermal protection performance. Here, an ultralight, mechanically robust, and thermally insulating polyimide (PI) aerogel is directly synthesized via constructing 3D interlocked curly nanofibrous networks during electrospinning. Controlling the solution/water molecule interaction enables the rapid phase inversion of charged jets, while the multiple jets are ejected by regulating charge density of the fluids, thus synergistically allowing numerous curly nanofibers to interlock and cross-link with each other to form porous aerogel structure. The resulted PI aerogel integrates the ultralight property with density of 2.4 mg cm-3, extreme temperature tolerance (mechanical robustness over -196 to 300 °C), and thermal insulation performance with ultralow thermal conductivity of 22.4 mW m-1 K-1, providing an ideal candidate to keep human thermal comfort under extreme temperature. This work can provide a source of inspiration for the design and development of nanofibrous aerogels for various applications.

Exploring the versatility of biodegradable biomass aerogels: In-depth evaluation of Firmiana simplex bark microfibers depolymerized by deep eutectic solvent.

In this study, we investigated the use of deep eutectic solvents (DESs) at different molar ratios and temperatures as a green and efficient approach for microfibers (MFs) extraction. Our approach entailed the utilization of Firmiana simplex bark (FSB) fibers, enabling the production of different dimensions of FSB microfibers (FSBMFs) by combining DES pretreatment and mechanical disintegration technique. The proposed practice demonstrates the simplicity and effectiveness of the method. The morphology of the prepared microfibers was studied using the Scanning electron microscopic (SEM) technique. Additionally, the results revealed that the chemical and mechanical treatments did not significantly alter the well-preserved cellulose structure of microfibers, and a crystallinity index of 56.6 % for FSB fibers and 63.8 % for FSBMFs was observed by X-ray diffraction (XRD) analysis. Furthermore, using the freeze-drying technique, FSBMFs in water solutions produced effective aerogels for air purification application. In comparison to commercial mask (CM), FSBMF aerogels' superior hierarchical cellular architectures allowed them to attain excellent filtration efficiencies of 94.48 % (PM10) and 91.51 % (PM2.5) as well as excellent degradation properties were analyzed. The findings show that FSBMFs can be extracted from Firmiana simplex bark, a natural cellulose-rich material, using DES for environmentally friendly aerogel preparation and applications.

Platelet Vesicles Synergetic with Biosynthetic Cellulose Aerogels for Ultra-Fast Hemostasis and Wound Healing.

Achieving hemostasis in penetrating and irregular wounds is challenging because the hemostasis factor cannot arrive at the bleeding site, and substantial bleeding will wash away the blood clot. Since the inherently gradual nature of blood clot formation takes time, a physical barrier is needed before blood clot formation. Herein, an ultra-light and shape memory hemostatic aerogel consisting of oxidized bacterial cellulose (OBC) and platelet extracellular vesicles (pVEs) is reported. The OBC-pVEs aerogel provides a physical barrier for the bleeding site by self-expansion, absorbing the liquid from blood to concentrate platelets and clotting factors and accelerating the clot formation by activating platelets and transforming fibrinogen into fibrin. In the rat liver and tail injury models, the blood loss decreases by 73% and 59%, and the bleeding times are reduced by 55% and 62%, respectively. OBC-pVEs aerogel has also been shown to accelerate wound healing. In conclusion, this work introduces an effective tool for treating deep, non-compressible, and irregular wounds and offers valuable strategies for trauma bleeding and wound treatment.

Scalable Ultralight Wood-Inspired Aerogel with Vertically Aligned Micrometer Channels for Highly Efficient Solar Interfacial Desalination.

An ultralight material that simultaneously combines remarkably rapid water transportation, highly efficient photothermal conversion, and excellent thermal insulation is highly desired for solar-driven interfacial desalination but was challenging. In this work, inspired by the unique natural structure of wood, we developed an ultralight aerogel by ice-templated synthesis as an integrated interfacial evaporator for solar-driven water production. The interior features vertically aligned biomimetic microscale channels facilitating rapid transportation of water molecules, while an improved photothermal interface allows high solar absorption and conversion via nonradiative relaxation and molecular vibrations. The biomimetic aerogel is ultralight with a density as low as 0.06 g/cm3, especially its fabrication is size- and shape-programmable as a whole and easily scalable. Additionally, the outstanding thermal insulation of the aerogel focuses heat precisely at the evaporation interface, reducing ineffective heat loss, while the uniformly distributed large-sized channels promote the dynamic convection of high concentration salt ions on the evaporator surface. Consequently, the evaporator shows broadband light absorption of 92.7%, leading to a water evaporation rate reaching 4.55 kg m-2 h-1 under 3 simulated solar irradiations, much higher than that of other reported evaporators with randomly distributed pores. This work provides new insight into advanced hybrid aerogels for highly efficient and durable solar-driven interfacial desalination systems.

Ultralight Ceramic Fiber Aerogel for High-Temperature Thermal Superinsulation.

Emerging fiber aerogels with excellent mechanical properties are considered as promising thermal insulation materials. However, their applications in extreme environments are hindered by unsatisfactory high-temperature thermal insulation properties resulting from severely increased radiative heat transfer. Here, numerical simulations are innovatively employed for structural design of fiber aerogels, demonstrating that adding SiC opacifiers to directionally arranged ZrO2 fiber aerogels (SZFAs) can substantially reduce high-temperature thermal conductivity. As expected, SZFAs obtained by directional freeze-drying technique demonstrate far superior high-temperature thermal insulation performance over existing ZrO2-based fiber aerogels, with a thermal conductivity of only 0.0663 W·m-1·K-1 at 1000 °C. Furthermore, SZFAs also exhibit excellent comprehensive properties, including ultralow density (6.24-37.25 mg·cm-3), superior elasticity (500 compression cycles at 60% strain) and outstanding heat resistance (up to 1200 °C). The birth of SZFAs provides theoretical guidance and simple construction methods for the fabrication of fiber aerogels with excellent high-temperature thermal insulation properties used for extreme conditions.

Facile fabrication of ultra-light N-doped-rGO/g-C3N4 for broadband microwave absorption.

"Thin thickness", "lightweight", "wide absorption bandwidth" and "strong absorption" are the new standards of contemporary science and technology for microwave absorption(MA) material. In this study, N-doped-rGO/g-C3N4 MA material was prepared for the first time by simple heat treatment, which the N atoms were doped into rGO and g-C3N4 was dispersed on the surface of N-doped-rGO, and its density is only 0.035 g/cm3. The impedance matching of the N-doped-rGO/g-C3N4 composite was well adjusted by decreasing the dielectric constant and attenuation constant due to the g-C3N4 semiconductor property and the graphite-like structure. Moreover, the distribution of g-C3N4 among N-doped-rGO sheets can produce more polarization effect and relaxation effect by increasing the lamellar spacing. Furthermore, the polarization loss of N-doped-rGO/g-C3N4 could be increased successfully by doping N atoms and g-C3N4. Ultimately, the MA property of N-doped-rGO/g-C3N4 composite was optimized significantly, with a loading of 5 wt%, the N-doped-rGO/g-C3N4 composite exhibited the RLmin of -49.59 dB and the effective absorption bandwidth could reach 4.56 GHz when the thickness was only 1.6 mm. The "thin thickness", "lightweight", "wide absorption bandwidth" and "strong absorption" of MA material are actually achieved by the N-doped-rGO/g-C3N4.