Direct synthesis of highly stretchable ceramic nanofibrous aerogels via 3D reaction electrospinning

Overview of Aerogels for Thermal Insulation

With the development of building energy efficiency, battery thermal management, aerospace, and other fields, the performance requirements of thermal insulation materials are increasing. Aerogels are porous materials with three-dimensional nanostructures with extremely low density and thermal conductivity. In recent years, aerogels have attracted much attention in thermal insulation due to their excellent properties. This paper reviews the design, preparation, and thermal insulation application of aerogels. First, the preparation methods of oxides, carbides, nitrides, and polymer aerogels are introduced. Then, the application progress of aerogels in various thermal insulation scenarios is analyzed. In addition, the challenges and prospects of future research on aerogels for thermal insulation are discussed.

Highly Oriented SiC@SiO2 Ceramic Fiber Aerogels with Good Anisotropy of the Thermal Conductivity and High-Temperature Resistance

Here electrospinning and freeze-drying techniques are combined to fabricate an anisotropic SiC@SiO2 ceramic fiber aerogels (A-SiC@SiO2-FAs). The anisotropic structure of the A-SiC@SiO2-FAs features aligned layers stacking layer-by-layer with the same direction and highly oriented 1D fibers inside each layer. The A-SiC@SiO2-FAs exhibit anisotropic thermal properties with an extremely low thermal conductivity of 0.018 W m-1 K-1 in the transverse direction (perpendicular to the SiC@SiO2 nanofibers) and ≈5 times higher thermal conductivity of 0.0914 W m-1 K-1 in the axial direction due to the highly oriented SiC@SiO2 nanofibers. The anisotropy factor of the A-SiC@SiO2-FAs is as high as 5.08, which exceeds most of the currently reported thermal insulation materials with anisotropic structural design, such as anisotropic wood aerogels, biaxially anisotropic PI/BC aerogels and anisotropic MXene foam, etc. The A-SiC@SiO2-FAs also have excellent thermal stability, maintaining structural integrity in oxidative environments at temperatures up to 1300 °C. Moreover, these structurally distinct A-SiC@SiO2-FAs result in superior elastic deformation with a radial recoverable strain exceeding 60% and an axial specific modulus of 5.72 kN m kg-1. These findings emphasize the potential of SiC nanofiber aerogels in extreme thermal environments and provide valuable insights for designing anisotropic insulation materials.

Silicon Carbide Aerogels: Fabrication, Properties, and Applications

Silicon carbide (SiC) aerogels are advanced materials distinguished by their low density, high porosity, exceptional thermal resistance, and tunable dielectric properties, making them highly promising for applications in thermal insulation, environmental protection, and electromagnetic wave absorption. Despite their potential, the fabrication of SiC aerogels with optimized performance presents significant challenges, including scalability issues, cost constraints, and difficulties in achieving precise control over material properties and architectures. This review comprehensively examines fabrication methods for SiC aerogels, such as sol-gel processing, electrospinning, 3D printing, and emerging synthesis techniques. It emphasizes their impact on key properties, including thermal conductivity, chemical stability, and mechanical properties. The recent advancements in the application of SiC aerogels for thermal insulation, electromagnetic wave absorption, environmental protection, sensing, and catalysis are discussed. This review concludes with an evaluation of the advantages and limitations of SiC aerogels and proposes future research directions to support their broader industrial adoption.

Integration of high strength, flexibility, and room-temperature plasticity in ceramic nanofibers

The developing cutting-edge technologies involving extreme mechanical environments, such as high-frequency vibrations, mechanical shocks, or repeated twisting, require ceramic components to integrate high strength, large bending strain, and even plastic deformation, which is difficult in conventional ceramic materials. The emergence of ceramic nanofibers (CNFs) offers potential solutions; unfortunately, this desirable integration of mechanical properties in CNFs remains unrealized to date, due to challenges in precisely modulating microstructures, reducing cross-scale defects, and overcoming inherent contradictions between mechanical attributes (particularly, high strength and large deformation are often mutually exclusive). Here, we report a nucleation regulation strategy for crystalline/amorphous dual-phase CNFs, achieving an extraordinary integration of high strength, superior flexibility, and room-temperature plasticity. This advancement stems from the optimized dual-phase structure featuring reduced nanocrystal aggregation, increased internal interfaces, and the elimination of fiber defects, thus fully activating the synergistic advantages and multiple deformation mechanisms of dual-phase configurations. Using TiO2, which is typically characterized by brittleness and low strength, as the proof-of-concept model, in-situ single-nanofiber mechanical tests demonstrate excellent flexibility, strength (~1.06 GPa), strain limit (~8.44%), and room-temperature plastic deformation. These findings would provide valuable insights into the mechanical design of ceramic materials, paving the way for CNFs in extreme applications and their widespread industrialization.

Nanofiber Aerogel with Rigidity-Flexibility Synergy

In aerogel-based thermal insulation materials, the challenge of balancing mechanical properties (rigidity and flexibility) while enhancing thermal performance under extreme temperature and humidity conditions persists. This study introduces an innovative biomimetic aerogel design combining features of shell-like layered architecture and loofah porous microstructures. We developed polyimide/polyvinylidene fluoride (PI/PVDF) nanofiber aerogels with excellent thermal insulation and mechanical properties. The material can withstand compressive loads up to 1500 times its weight with axial rigidity, while maintaining radial flexibility under 80% strain, thereby achieving a harmonious balance between structural rigidity and flexibility. The inclusion of hydrophobic PVDF nanofibers ensures the material maintains low thermal conductivity and structural integrity, even under extreme humidity and temperature changes. This multifeature fusion biomimetic aerogel shows great potential for aerospace applications, such as spacecraft thermal protection systems, effectively shielding components from thermal and mechanical stress during re-entry and space missions.

Multimode Thermal Gating Based on Elastic Ceramic-Carbon Nanowhisker/Nanofiber Aerogels by Strain Engineering Strategy

The capability to regulate heat transport dynamically and reversibly within solid materials propels advancement in aerospace conditioning, battery thermal control, and energy harvesting/conversion industries. Although aerogels are known for thermal insulation properties, their constant thermal resistance induced by immutable pore structure makes them struggle to reverse-release the accumulated thermal energy. Here, we develop a nanocrystalline whisker/nanofiber aerogel (WFA) thermal gating induced by the self-catalyzed growth strategy, whose elasticity offers possibilities for dynamic thermal management. Thermal conductivities can be continuously regulated by external compressive strain-trigged heat conduction pathway and interfacial resistance variations, switching seamlessly between 0.020 W m-1 K-1 in an uncompressed state and 0.071 W m-1 K-1 at 80% compressive strain, with a modulation ratio of ∼3.55. The integral inorganic nature ensures the thermal stability of WFAs over a large thermal gradient, from -196 °C deep cryogenic to 1500 °C ultrahigh temperature. The resulting multimode WFAs provide a feasible solution for thermal management in extreme environments.

SiO2-based inorganic nanofiber aerogel with rapid hemostasis and liver wound healing functions

Non-compressible hemostasis and promoting tissue healing are important in soft tissue trauma repair. Inorganic aerogels show superior performance in rapid hemostasis or promoting tissue healing, but simultaneously promoting non-compressive hemostasis and soft tissue healing still remains a challenge. Herein, SiO2-based inorganic nanofiber aerogels (M2+@SiO2, M=Ca, Mg, and Sr) were prepared by freeze-drying the mixture of bioactive silicates-deposited SiO2 nanofibers and SiO2 sol. These M2+@SiO2 aerogels have a three-dimensional highly-interconnected porous structure, remarkable flexibility, high absorption, good hydrophilicity, negative zeta potential, and bioactive ions releasing capacity. M2+@SiO2 aerogels not only exhibited satisfactory hemostasis activities in vitro, but also possessed high hemostatic efficacy in compressible rabbit femoral artery injury bleeding model and non-compressible rat liver puncture bleeding model compared to medical gauze and gelatin sponge. M2+@SiO2 aerogel had low blood clotting index of Ca. 10 % and short partial thromboplastin time of ca. 82 s in vitro, and could greatly short bleeding time by >50 % and decrease blood loss by about 80 % compared to medical gauze and gelatin sponge in non-compressible hemostasis. Sr2+@SiO2 aerogel showed optimal bioactivities on promoting cell proliferation, cell migration, and the expression of liver function and angiogenesis related genes and proteins in vitro. Importantly, Sr2+@SiO2 aerogel possessed a noteworthy function to promote liver soft tissue healing in vivo by releasing bioactive ions and providing a highly-interconnected porous structure to support vascular development and tissue regeneration. Overall, Sr2+@SiO2 aerogel has great potential for integrated rapid hemostasis and soft tissue healing, which is promising in soft tissue trauma therapy. STATEMENT OF SIGNIFICANCE: Non-compressible hemorrhage and soft tissue impairment are the main causes of mortality in emergency trauma. Inorganic aerogels with high porosity and outstanding flexibility can rapidly absorb blood to pro-coagulation and fill in irregular trauma without compression, but the low bioactivity limited the ability to promote soft tissue healing. Herein, SiO2-based inorganic nanofiber aerogels (M2+@SiO2, M=Ca, Mg, and Sr) were prepared by freeze-drying the mixture of bioactive silicates-deposited SiO2 nanofibers and SiO2 sol. M2+@SiO2 aerogels possessed high bioactivity and exhibited superior hemostatic performance in compressible and non-compressible bleeding model. Furthermore, Sr2+@SiO2 aerogel showed optimal bioactivities on cell responses and effectively promoted liver healing by releasing bioactive ions and providing highly-interconnected porous support structure for vascular development and tissue regeneration.

Ultralight, Elastic, Thermally Insulating, and High-Temperature Resistant Al2O3-SiO2-B2O3 Nanofibrous Aerogels Prepared via the Direct Foaming Method

Ceramic nanofibrous aerogels exhibit ultralow density and thermal conductivity, which make them ideal candidates for thermal protection in extreme environments. However, the current limitations in pore-forming techniques hinder their further advancement. In this study, ultralight, highly elastic, and high-temperature-resistant ceramic nanofibrous aerogels were successfully prepared through the direct foaming method using flexible Al2O3-SiO2-B2O3 nanofibers as raw materials and Tween 80 as the foaming agent. Foams generated in the slurry exhibited exceptional stability, facilitating the formation of a porous three-dimensional network structure with nonoriented pores and tightly bonded fiber connections within the green body after the drying process. This porous structure was obtained via sintering and maintained stability at temperatures up to 1000 °C. In addition, the porosity was controlled by adjusting the content of the foaming agent. An increase in the Tween 80 dosage resulted in a higher number of air bubbles per unit volume within the slurry, accompanied by a decrease in their sizes. Consequently, the structure possessed abundant pores with small sizes, promoting gradual deterioration in fiber junctions. As a result, the aerogels demonstrated a decrease in density and elasticity as well as improved thermal insulation properties. These findings provide novel insights for the preparation and performance regulation of ceramic nanofibrous aerogels.

Recent Advances in Next-Generation Textiles

Textiles have played a pivotal role in human development, evolving from basic fibers into sophisticated, multifunctional materials. Advances in material science, nanotechnology, and electronics have propelled next-generation textiles beyond traditional functionalities, unlocking innovative possibilities for diverse applications. Thermal management textiles incorporate ultralight, ultrathin insulating layers and adaptive cooling technologies, optimizing temperature regulation in dynamic and extreme environments. Moisture management textiles utilize advanced structures for unidirectional transport and breathable membranes, ensuring exceptional comfort in activewear and outdoor gear. Protective textiles exhibit enhanced features, including antimicrobial, antiviral, anti-toxic gas, heat-resistant, and radiation-shielding capabilities, providing high-performance solutions for healthcare, defense, and hazardous industries. Interactive textiles integrate sensors for monitoring physical, chemical, and electrophysiological parameters, enabling real-time data collection and responses to various environmental and user-generated stimuli. Energy textiles leverage triboelectric, piezoelectric, and hygroelectric effects to improve energy harvesting and storage in wearable devices. Luminous display textiles, including electroluminescent and fiber optic systems, enable dynamic visual applications in fashion and communication. These advancements position next-generation textiles at the forefront of materials science, significantly expanding their potential across a wide range of applications.

3D Printing of Porous Ceramics for Enhanced Thermal Insulation Properties

Porous thermal insulating ceramics play a pivotal role in both industrial processes and daily life by offering effective insulation solutions that reduce energy consumption, enhance building comfort, and contribute to the sustainability of industrial production. This review offers a comprehensive examination of porous thermal insulating ceramics produced by 3D printing, providing an in-depth analysis of various 3D printing techniques and materials used to produce porous ceramics, detailing the fabrication processes, advantages, and limitations of these methods. Recent advances in 3D printed porous thermal insulating ceramics are thoroughly examined, with a particular focus on pore structure design and optimization strategies for high-performance thermal insulation. This review also addresses the challenges and barriers to widespread adoption while highlighting future research directions and emerging trends poised to drive innovation. By showcasing the transformative potential of 3D printing in revolutionizing traditional porous ceramics manufacturing methods and enhancing thermal insulation performance, this review underscores the critical role of 3D printed porous ceramics in advancing thermal insulation technology.

Fire-Safe Aerogels and Foams for Thermal Insulation: From Materials to Properties

The ambition of human beings to create a comfortable environment for work and life in a sustainable way has triggered a great need for advanced thermal insulation materials in past decades. Aerogels and foams present great prospects as thermal insulators owing to their low density, good thermal insulation, mechanical robustness, and even high fire resistance. These merits make them suitable for many real-world applications, such as energy-saving building materials, thermally protective materials in aircrafts and battery, and warming fabrics. Despite great advances, to date there remains a lack of a comprehensive yet critical review on the thermal insulation materials. Herein, recent progresses in fire-safe thermal-insulating aerogels and foams are summarized, and pros/cons of three major categories of aerogels/foams (inorganic, organic and their hybrids) are discussed. Finally, key challenges associated with existing aerogels are discussed and some future opportunities are proposed. This review is expected to expedite the development of advanced aerogels and foams as fire-safe thermally insulating materials, and to help create a sustainable, safe, and energy-efficient society.

Programmable Shape-Morphing Enables Ceramic Meta-Aerogel Highly Stretchable for Thermal Protection

Ceramic aerogels hold significant potential for thermal insulation, yet their mechanical stretchability and thermal stability fall short in extreme environments. Here, the study presents a programmable shape-morphing strategy aimed at engineering a binary network topology structure within ceramic aerogels to effectively dissipate stress and block heat transfer. The special topology design, which includes kirigami lamellated aerogels for bearing loading stress and randomly assembled aerogels for mechanical energy pre-storage to transfer tensile stress, effectively achieves unexpected mechanical tensile properties and thermal stability. The resulting robust meta-aerogels demonstrate remarkable structural stability with topology-derived mechanical tensile of up to 85% strain, excellent resilience to 500 cycles of 50% tensile strain, 1000 cycles of 60% buckling strain, and 500 cycles of 50% compressive strain, temperature-invariant tensile recovery capability; simultaneously, low thermal conductivity of 33.01 mW m-1 K-1 and tensile-invariant thermal insulation makes the ceramic meta-aerogels an ideal substitute material for various applications.

Highly-Buckled Nanofibrous Ceramic Aerogels with Ultra-Large Stretchability and Tensile-Insensitive Thermal Insulation

Ceramic aerogels have exhibited many superior characteristics with promising applications. As an attractive material system for thermal insulation under extreme conditions, ceramic aerogels are required to withstand complex thermomechanical stress to retain their super-insulating properties but, they often suffer from severe fracture damage that can lead to catastrophic failure. Herein, inspired by the tendrils of Parthenocissus, we report a design and synthesis of ultra-stretchable ceramic aerogels constructed by highly buckled nanofibers. The buckling of nanofibers is formed by asymmetric deformation through two-component off-axial electrospinning method. The resulting aerogels feature an ultra-large stretchability with a tensile strain of up to 150% and high restorability with a tensile strain of up to 80%. They also display a near-zero Poisson's ratio (4.3 × 10-2) and a near-zero thermal expansion coefficient (2.6 × 10-7 per °C), resulting in excellent thermomechanical stability. Benefiting from this ultra-stretchability, the aerogels exhibit a unique tensile-insensitive thermal insulation performance with thermal conductivities remaining only ≈106.7 mW m-1 K-1 at 1000 °C. This work promotes the development of ceramic aerogels for robust thermal insulation under extreme conditions and establishes a set of fundamental considerations in structural design of stretchable aerogels for a wide spectrum of applications.

Achieving Robust α-Alumina Nanofibers by Ligand Confinement Coupled with Local Disorder Tuning

As high-performance thermal protection and structure enhancement materials, oxide ceramic fibers have become indispensable in numerous areas, ranging from deep-sea exploration to supersonic aircraft. However, under extreme energy input, abnormal grain growth and inevitable vermiculate structure would break the fiber integrity, causing catastrophic structure failure. Nowadays, the design of nanoceramics brings potential answers for strengthening of mechanical properties, but with the diameter downsized to the nanoscale, the increasing structural susceptibility of ceramic fiber to phase transformation and grain growth becomes a huge barrier. Here, we propose a strong carboxylic ligand confinement strategy by the combination of formic and acetic acids to control the inorganic colloid growth for fabricating robust α-alumina nanofibers. The rapid hydrolysis and coordination of the carboxylate groups with aluminum together with subsequent concentration synergistically promote the formation of small and compact precursor colloids, laying a solid foundation for suppressing abnormal grain growth and achieving refined alumina grain structure. The local disorder induced by silica and boron oxide surrounding α-alumina grains imparts excellent mechanical properties and flexibility with no fractures observed even after 500 buckling cycles and a wide range of temperatures from -196 to 1100 °C, providing an enlightening paradigm for ceramic fiber strengthening.

Mechanically Robust Triboelectric Aerogels Enabled by Dense Bridging of MXene

Aerogels are widely applied for construction, aerospace, military, and energy owing to their lightweight, high specific surface area, and high porosity. The high porosity of aerogels often leads to a lack of mechanical strength, which limits their applications. Here, this study reports a mechanically robust MXene/cellulose nanocrystal composite aerogel enabled by inducing dense bridging through salting-out. First, MXene sheets are bridged with cellulose molecular chains via hydrogen bonds, and further dense bridging is constructed by promoting hydrogen bond formation through salting-out. By enhancing hydrogen bonding, the interlayer spacing of MXene sheets is reduced and their orientation is improved, effectively increasing the energy dissipation capacity of the porous structure. The aerogel exhibits a Young's modulus of 72.4 MPa, a specific modulus of 342.0 kN m/kg. An aerogel is used as a triboelectric material to construct a highly robust triboelectric nanogenerator. This study provides an effective strategy for the preparation of the mechanically robust aerogels.

Industrial Scale Sea-Island Melt-Spun Continuous Ultrafine Fibers for Highly Comfortable Insulated Aerogel Felt Clothing

Aerogels are most attractive for thermal clothing. However, mechanical fragility and structural instability restrict their practical applications. These issues are overcome by developing industrial scale sea-island melt-spun ultrafine fibers with large and uniform length-to-diameter as building blocks, which are assembled into aerogel felts with corrugated lamellar structure through freeze-shaping technology. These aerogels possess excellent mechanical properties to meet fabric elasticity and comfort needs, including super-flexibility (25% tensile strain, 95% compression, 180° bending performance) and fatigue resistance of over 10,000 cycles. The aerogels are also self-cleaning, waterproof, breathable, and flame-retardant, making them suitable for application requirements in extreme environments. Moreover, the obtained aerogel felt clothing exhibits excellent thermal insulation properties close to that of dry air, and is only one-third as thick as down clothing with similar insulating properties. Expanding sea-island melt-spun fiber to construct aerogel in this strategy provides scalable potential for developing multifunctional insulating aerogel clothing.

Confined Gelation Synthesis of Flexible Barium Aluminate Nanofibers as a High-Performance Refractory Material

Barium aluminate (BAO) ceramics are highly sought after as a kind of high-temperature refractory material due to their exceptional thermal stability in both vacuum and oxygen atmospheres, but their inherent brittleness results in rapid hardening, imposing a negative impact on the overall construction performance. Here, we report a strategy to synthesize flexible BAO nanofibers with a needle-like structure through confined-gelation electrospinning followed by in situ mineralization. The confined gelation among the colloidal particles promotes the formation of precursor nanofibers with high continuity and a large aspect ratio. The resulting flexible BAO nanofiber membranes are bendable, stretchable, and can even be woven, exhibiting a softness (12 mN) that is lower than that of tissue paper (27 mN). Additionally, they are capable of withstanding hundreds to thousands of continuous buckling and bending at 50% deformation without tearing. More importantly, the low emissivity of the flexible BAO nanofiber membranes ensures excellent thermal insulation at 1300 °C while preserving structural integrity and performance stability. In this sense, our strategy can be easily scaled up to produce flexible yet tough oxide ceramic membranes for a wider range of applications.

Microstructural evolution of bio-based chitosan aerogels for thermal insulator with superior moisture/fatigue resistance and anti-thermal-shock

Bio-based aerogel is a functionalized nanoporous material with environmentally friendly, high surface area, ultra-low density, high porosity, and low thermal conductivity, making it suitable for various applications such as energy-saving buildings, electronic information, separation, adsorption, catalysis, biomedicine, and others. However, the current bio-based chitosan aerogel still faces great challenges in reaching multifunctional improvement to address its intrinsic shortcomings. Herein, we propose a new approach depending upon supramolecular interactions for constructing chitosan/bacterial cellulose aerogels that simultaneously possess superior moisture resistance/fatigue, anti-thermal-shock, and flame retardancy. Specifically, the aerogels demonstrate remarkable characteristics, namely high strength (self-standing itself weight beyond 10,676 times), low thermal conductivity (lowest to 22 mW m-1 K-1 under normal pressure and room temperature), and excellent fatigue resistance (almost negligible permanent deformation at 1 % strain even undergoing compressive cycles up to 10,000 times). On the other hand, the aerogels display exceptional moisture resistance with superhydrophobicity (moisture absorption rate <0.88 % for 160 h at 70 °C and 85 % relative humidity), excellent thermal shock property (withstand cold-hot shock up to 200 cycles with rapid temperature changes between -30 °C and 60 °C), and remarkable fire retardancy (swiftly self-extinguishing in 0.6 s). Additionally, the compressive stress increases to 0.223 MPa at 3 % strain after hydrophobic treatment, representing a 27 % enhancement in mechanical robustness. Further, the mechanism responsible for microstructural evolution has been also established in different strain conditions. This work may provide rich possibilities for developing multifunctional bio-based aerogel for energy-saving buildings.

Fibres-threads of intelligence-enable a new generation of wearable systems

Fabrics represent a unique platform for seamlessly integrating electronics into everyday experiences. The advancements in functionalizing fabrics at both the single fibre level and within constructed fabrics have fundamentally altered their utility. The revolution in materials, structures, and functionality at the fibre level enables intimate and imperceptible integration, rapidly transforming fibres and fabrics into next-generation wearable devices and systems. In this review, we explore recent scientific and technological breakthroughs in smart fibre-enabled fabrics. We examine common challenges and bottlenecks in fibre materials, physics, chemistry, fabrication strategies, and applications that shape the future of wearable electronics. We propose a closed-loop smart fibre-enabled fabric ecosystem encompassing proactive sensing, interactive communication, data storage and processing, real-time feedback, and energy storage and harvesting, intended to tackle significant challenges in wearable technology. Finally, we envision computing fabrics as sophisticated wearable platforms with system-level attributes for data management, machine learning, artificial intelligence, and closed-loop intelligent networks.

Elastic SiC Aerogel for Thermal Insulation: A Systematic Review

SiC aerogels with their lightweight nature and exceptional thermal insulation properties have emerged as the most ideal materials for thermal protection in hypersonic vehicles; However, conventional SiC aerogels are prone to brittleness and mechanical degradation when exposed to complex loads such as shock and mechanical vibration. Hence, preserving the structural integrity of aerogels under the combined influence of thermal and mechanical external forces is crucial not only for stabling their thermal insulation performance but also for determining their practicality in harsh environments. This review focuses on the optimization of design based on the structure-performance of SiC aerogels, providing a comprehensive review of the inherent correlations among structural stability, mechanical properties, and insulation performance. First, the thermal transfer mechanism of aerogels from a microstructural perspective is studied, followed by the relationship between the building blocks of SiC aerogels (0D particles, 1D nanowires/nanofibers) and their compression performance (including compressive resilience, compressive strength, and fatigue resistance). Moreover, the strategy to improve the high-temperature oxidation resistance and insulation performance of SiC aerogels is explored. Lastly, the challenges and future breakthrough directions for SiC aerogels are presented.

Multiphase Symbiotic Engineered Elastic Ceramic-Carbon Aerogels with Advanced Thermal Protection in Extreme Oxidative Environments

Elastic aerogels can dissipate aerodynamic forces and thermal stresses by reversible slipping or deforming to avoid sudden failure caused by stress concentration, making them the most promising candidates for thermal protection in aerospace applications. However, existing elastic aerogels face difficulties achieving reliable protection above 1500 °C in aerobic environments due to their poor thermomechanical stability and significantly increased thermal conductivity at elevated temperatures. Here, a multiphase sequence and multiscale structural engineering strategy is proposed to synthesize mullite-carbon hybrid nanofibrous aerogels. The heterogeneous symbiotic effect between components simultaneously inhibits ceramic crystalline coarsening and carbon thermal etching, thus ensuring the thermal stability of the nanofiber building blocks. Efficient load transfer and high interfacial thermal resistance at crystalline-amorphous phase boundaries on the microscopic scale, coupled with mesoscale lamellar cellular and locally closed-pore structures, achieve rapid stress dissipation and thermal energy attenuation in aerogels. This robust thermal protection material system is compatible with ultralight density (30 mg cm-3), reversible compression strain of 60%, extraordinary thermomechanical stability (up to 1600 °C in oxidative environments), and ultralow thermal conductivity (50.58 mW m-1 K-1 at 300 °C), offering new options and possibilities to cope with the harsh operating environments faced by space exploration.

Ultrathin aerogel-structured micro/nanofiber metafabric via dual air-gelation synthesis for self-sustainable heating

Incorporating passive heating structures into personal thermal management technologies could effectively mitigate the escalating energy crisis. However, current passive heating materials struggle to balance thickness and insulating capability, resulting in compromised comfort, space efficiency, and limited thermoregulatory performance. Here, a dual air-gelation strategy, is developed to directly synthesize ultrathin and self-sustainable heating metafabric with 3D dual-network structure during electrospinning. Controlling the interactions among polymer, solvent, and water enables the microphase separation of charged jets, while adjusting the distribution of carbon black nanoparticles within charged fluids to form fibrous networks composed of interlaced aerogel micro/nanofibers with heat storage capabilities. With a low thickness of 0.18 mm, the integrated metafabric exhibits exceptional thermal insulation performance (15.8 mW m-1K-1), superhydrophobicity, enhanced mechanical properties, and high breathability while maintaining self-sustainable radiative heating ability (long-lasting warming of 8.8 °C). This strategy provides rich possibilities to develop advanced fibrous materials for smart textiles and thermal management.

Significantly Enhanced Mechanical, Thermal, and Ablative Properties of the Lightweight Carbon Fabric/Phenol-Formaldehyde Resin/Siloxane Aerogels Ternary Interpenetrating Network

Lightweight ablative thermal protection materials (TPMs), which can resist long-term ablation in an oxidizing atmosphere, are urgently required for aerospace vehicles. Herein, carbon fabric/phenol-formaldehyde resin/siloxane aerogels (CF/PFA/SiA) nanocomposite with interpenetrating network multiscale structure was developed via simple and efficient sol-gel followed by atmospheric pressure drying. The ternary networks structurally interpenetrating in macro-, micron-, and the nanoscales, chemically cross-linking at the molecular scale, and silica layer generated by in situ heating synergistically bring about low density (∼0.3 g cm-3), enhanced mechanical properties, thermal stability, and oxidation resistance, and a low thermal conductivity of 81 mW m-1 K-1. More intriguingly, good thermal protection with near-zero surface recession at 1300 °C for 300 s and remarkable thermal insulation with a back-side temperature below 60 °C at 20 mm thickness. The interpenetrating network strategy can be extended to other porous components with excellent high-temperature properties, such as ZrO2 and SiC, which will facilitate the improvement of lightweight ablative TPMs. Moreover, it may open a new avenue for fabricating multifunctional binary, ternary, and even multiple interpenetrating network materials.

TiO2/SiO2 spiral crimped Janus fibers engineered for stretchable ceramic membranes with high-temperature resistance

The tensile brittleness of ceramic nanofibrous materials makes them unable to withstand the relatively large fracture strain, greatly limiting their applications in extreme environments such as high or ultra-low temperatures. Herein, highly stretchable and elastic ceramic nanofibrous membranes composed of titanium dioxide/silicon dioxide (TiO2/SiO2) bicomponent spiral crimped Janus fibers were designed and synthesized via conjugate electrospinning combined with calcination treatment. Owing to the opposite charges attached, the two fibers assembled side by side to form a Janus structure. Interestingly, radial shrinkage differences existed on the two sides of the TiO2/SiO2 composite nanofibers, constructing a helical crimp structure along the fiber axis. The special configuration effectively improves the stretchability of TiO2/SiO2 ceramic nanofibrous membranes, with up to 70.59% elongation at break, excellent resilience at 20% tensile strain and plastic deformation of only 3.48% after 100 cycles. Additionally, the relatively fluffy ceramic membranes constructed from spiral crimped Janus fibers delivered a lower thermal conductivity of 0.0317 W m-1 K-1, attributed to the increased internal still air content. This work not only reveals the attractive tensile mechanism of ceramic membranes arising from the highly curly nanofibers, but also proposes an effective strategy to make the ceramic materials withstand the complex dynamic strain in extreme temperature environments (from -196 °C to 1300 °C).

Building-Envelope-Inspired, Thermomechanically Robust All-Fiber Ceramic Meta-Aerogel for Temperature-Controlled Dominant Infrared Camouflage

The unsatisfactory properties of ceramic aerogels when subjected to thermal shock, such as strength degradation and structural collapse, render them unsuitable for use at large thermal gradients or prolonged exposure to extreme temperatures. Here, a building-envelope-inspired design for fabricating a thermomechanically robust all-fiber ceramic meta-aerogel with interlocked fibrous interfaces and an interwoven cellular structure in the orthogonal directions is presented, which is achieved through a two-stage physical and chemical process. Inspired by the reinforced concrete building envelope, a solid foundation composed of fibrous frames is constructed and enhanced through supramolecular in situ self-assembly to achieve high compressibility, retaining over 90% of maximum stress under a considerable compressive strain of 50% for 10 000 cycles, and showing temperature-invariance when compressed at 60% strain within the range of -100 to 500 °C. As a result of its distinct response to oscillation tolerance coupled with elastic recovery, the all-fiber ceramic meta-aerogel exhibits exceptional suitability for thermal shock resistance and infrared camouflage performance in cold (-196 °C) and hot (1300 °C) fields. This study provides an opportunity for developing ceramic aerogels for effective thermal management under extreme conditions.

Perspectives Toward Damage-Tolerant Nanostructure Ceramics

Advanced ceramic materials and devices call for better reliability and damage tolerance. In addition to their strong bonding nature, there are examples demonstrating superior mechanical properties of nanostructure ceramics, such as damage-tolerant ceramic aerogels that can withstand high deformation without cracking and local plasticity in dense nanocrystalline ceramics. The recent progresses shall be reviewed in this perspective article. Three topics including highly elastic nano-fibrous ceramic aerogels, load-bearing nanoceramics with improved mechanical properties, and implementing machine learning-assisted simulations toolbox in understanding the relationship among structure, deformation mechanisms, and microstructure-properties shall be discussed. It is hoped that the perspectives present here can help the discovery, synthesis, and processing of future structural ceramic materials that are insensitive to processing flaws and local damages in service.

Advancements in Thermal Insulation through Ceramic Micro-Nanofiber Materials

Ceramic fibers have the advantages of high temperature resistance, light weight, favorable chemical stability and superior mechanical vibration resistance, which make them widely used in aerospace, energy, metallurgy, construction, personal protection and other thermal protection fields. Further refinement of the diameter of conventional ceramic fibers to microns or nanometers could further improve their thermal insulation performance and realize the transition from brittleness to flexibility. Processing traditional two-dimensional (2D) ceramic fiber membranes into three-dimensional (3D) ceramic fiber aerogels could further increase porosity, reduce bulk density, and reduce solid heat conduction, thereby improving thermal insulation performance and expanding application areas. Here, a comprehensive review of the newly emerging 2D ceramic micro-nanofiber membranes and 3D ceramic micro-nanofiber aerogels is demonstrated, starting from the presentation of the thermal insulation mechanism of ceramic fibers, followed by the summary of 2D ceramic micro-nanofiber membranes according to different types, and then the generalization of the construction strategies for 3D ceramic micro-nanofiber aerogels. Finally, the current challenges, possible solutions, and future prospects of ceramic micro-nanofiber materials are comprehensively discussed. We anticipate that this review could provide some valuable insights for the future development of ceramic micro-nanofiber materials for high temperature thermal insulation.

Janus silk fibroin/polycaprolactone-based scaffold with directionally aligned fibers and porous structure for bone regeneration

To promote bone repair, it is desirable to develop three-dimensional multifunctional fiber scaffolds. The densely stacked and tightly arranged conventional two-dimensional electrospun fibers hinder cell penetration into the scaffold. Most of the existing three-dimensional structural materials are isotropic and monofunctional. In this research, a Janus nanofibrous scaffold based on silk fibroin/polycaprolactone (SF/PCL) was fabricated. SF-encapsulated SeNPs demonstrated stability and resistance to aggregation. The outside layer (SF/PCL/Se) of the Janus nanofiber scaffold displayed a structured arrangement of fibers, facilitating cell growth guidance and impeding cell invasion. The inside layer (SF/PCL/HA) featured a porous structure fostering cell adhesion. The Janus fiber scaffold containing SeNPs notably suppressed S. aureus and E. coli activities, correlating with SeNPs concentration. In vitro, findings indicated considerable enhancement in alkaline phosphatase (ALP) activity of MC3T3-E1 osteoblasts and upregulation of genes linked to osteogenic differentiation with exposure to the SF/PCL/HA/Se Janus nanofibrous scaffold. Moreover, in vivo, experiments demonstrated successful critical bone defect repair in mouse skulls using the SF/PCL/HA/Se Janus nanofiber scaffold. These findings highlight the potential of the SF/PCL-based Janus nanofibrous scaffold, integrating SeNPs and nHA, as a promising biomaterial in bone tissue engineering.

Insights into Materials, Physics, and Applications in Flexible and Wearable Acoustic Sensing Technology

Sound plays a crucial role in the perception of the world. It allows to communicate, learn, and detect potential dangers, diagnose diseases, and much more. However, traditional acoustic sensors are limited in their form factors, being rigid and cumbersome, which restricts their potential applications. Recently, acoustic sensors have made significant advancements, transitioning from rudimentary forms to wearable devices and smart everyday clothing that can conform to soft, curved, and deformable surfaces or surroundings. In this review, the latest scientific and technological breakthroughs with insightful analysis in materials, physics, design principles, fabrication strategies, functions, and applications of flexible and wearable acoustic sensing technology are comprehensively explored. The new generation of acoustic sensors that can recognize voice, interact with machines, control robots, enable marine positioning and localization, monitor structural health, diagnose human vital signs in deep tissues, and perform organ imaging is highlighted. These innovations offer unique solutions to significant challenges in fields such as healthcare, biomedicine, wearables, robotics, and metaverse. Finally, the existing challenges and future opportunities in the field are addressed, providing strategies to advance acoustic sensing technologies for intriguing real-world applications and inspire new research directions.

Dual-Drug-Loaded Core-Shell Electrospun Nanofiber Dressing for Deep Burns

The epidermis of a deep burn wound is entirely absent and the dermal tissue sustains significant damage, accompanied by a substantial amount of tissue exudate. Due to the excessively humid environment, the formation of a scab on the wound becomes challenging, leaving it highly vulnerable to external bacterial invasion. In this work, a core-shell dual-drug-loaded nanofiber dressing was prepared by electrospinning technology for the synergistic treatment of a deep burn. The shell layer consists of polycaprolactone and chitosan encapsulating asiaticoside, with the core layer comprising the clathrate of 2-hydroxypropyl-β-cyclodextrin and curcumin. Upon application to the wound, the dual-drug-loaded nanofiber dressing exhibited rapid release of asiaticoside, stimulating collagen deposition and promoting tissue repair. The core-shell structure and clathrate configuration ensured sustained release of curcumin, providing antibacterial and anti-inflammatory functions for the wound. The mechanical strength, broad-spectrum antibacterial ability, cell proliferation, and adhesion ability of the nanofiber dressing showed its potential as a medical dressing. This dressing also exhibited excellent wound healing promoting effects in the SD rat burn model. This paper provides a strategy for burn wound healing.

Mechanically resilient hybrid aerogels containing fibers of dual-scale sizes and knotty networks for tissue regeneration

The structure and design flexibility of aerogels make them promising for soft tissue engineering, though they tend to come with brittleness and low elasticity. While increasing crosslinking density may improve mechanics, it also imparts brittleness. In soft tissue engineering, resilience against mechanical loads from mobile tissues is paramount. We report a hybrid aerogel that consists of self-reinforcing networks of micro- and nanofibers. Nanofiber segments physically entangle microfiber pillars, allowing efficient stress distribution through the intertwined fiber networks. We show that optimized hybrid aerogels have high specific tensile moduli (~1961.3 MPa cm3 g-1) and fracture energies (~7448.8 J m-2), while exhibiting super-elastic properties with rapid shape recovery (~1.8 s). We demonstrate that these aerogels induce rapid tissue ingrowth, extracellular matrix deposition, and neovascularization after subcutaneous implants in rats. Furthermore, we can apply them for engineering soft tissues via minimally invasive procedures, and hybrid aerogels can extend their versatility to become magnetically responsive or electrically conductive, enabling pressure sensing and actuation.

Biomimetic crimped/aligned microstructure to optimize the mechanics of fibrous hybrid materials for compliant vascular grafts

The precise mechanical properties of many tissues are highly dependent on both the composition and arrangement of the nanofibrous extracellular matrix. It is well established that collagen nanofibers exhibit a crimped microstructure in several tissues such as blood vessel, tendon, and heart valve. This collagen fiber arrangement results in the classic non-linear 'J-shaped' stress strain curve characteristic of these tissues. Synthetic biomimetic fibrous materials with a crimped microstructure similar to natural collagen demonstrate similar mechanical properties to natural tissues. The following work describes a nanofabrication method based on electrospinning used to fabricate two component hybrid electrospun fibrous materials that mimic the microstructure and mechanical properties of vascular tissue. The properties of these samples can be precisely and predictably optimized by modifying fabrication parameters. Tubular grafts with biomimetic microstructure were constructed to demonstrate the potential of this fabrication method in vascular graft replacement applications. It was possible to closely match both the overall geometry and the compliance of specific blood vessels by optimizing graft microstructure.

Nanotechnology-based bone regeneration in orthopedics: a review of recent trends

Nanotechnology has revolutionized the field of bone regeneration, offering innovative solutions to address the challenges associated with conventional therapies. This comprehensive review explores the diverse landscape of nanomaterials - including nanoparticles, nanocomposites and nanofibers - tailored for bone tissue engineering. We delve into the intricate design principles, structural mimicry of native bone and the crucial role of biomaterial selection, encompassing bioceramics, polymers, metals and their hybrids. Furthermore, we analyze the interface between cells and nanostructured materials and their pivotal role in engineering and regenerating bone tissue. In the concluding outlook, we highlight emerging frontiers and potential research directions in harnessing nanomaterials for bone regeneration.

Direct synthesis of ultralight, elastic, high-temperature insulation N-doped TiO2 ceramic nanofibrous sponges via conjugate electrospinning

The design of three-dimensional ceramic nanofibrous materials with high-temperature insulation and flame-retardant characteristics is of significant interest due to the effectively improved mechanical properties. However, achieving a pure ceramic monolith with ultra-low density, high elasticity and toughness remains a great challenge. Herein, a low-cost, scalable strategy to fabricate ultralight and mechanically robust N-doped TiO2 ceramic nanofibrous sponges with a continuous stratified structure by conjugate electrospinning is reported. Remarkably, the introduction of dopamine into the precursor nanofibers is engineered, which realizes the nitrogen doping to inhibit the TiO2 grain growth, endowing single nanofibers with a smoother, less defective surface. Besides, the self-polymerization process of dopamine allows the construction of bonding points between nanofibers and optimizes the distribution of inorganic micelles on polymer templates. Moreover, a rotating disk receiving device under different rotating speeds is designed to obtain N-doped TiO2 sponges with various interlamellar spacings, further affecting the maximum compressive deformation capacity. The resulting ceramic sponges, consisting of fluffy crosslinked nanofiber layers, possess low densities of 12-45 mg cm-3, which can quickly recover under a large strain of 80% and have only 9.2% plastic deformation after 100 compression cycles. In addition, the sponge also exhibits a temperature-invariant superelasticity at 25-800 °C and a low heat conductivity of 0.0285 W m-1 K-1, with an outstanding thermal insulation property, making it an ideal insulation material for high-temperature or harsh conditions.

Silver nanowire-infused carbon aerogel: A multifunctional nanocellulose-derived material for personal thermal management

Personal thermal management (PTM) textiles for outdoor activities have become increasingly important for addressing energy consumption and thermal comfortable. Cellulose nanofiber (CNF) aerogels have emerged as promising candidates for PTM due to the eco-friendliness, lightweight, and low thermal conductivity. However, the singular insulation capability may not be sufficient to accommodate the diverse and harsh outdoor conditions. Herein, we carbonized CNF-based aerogel to fabricate anisotropic carbon aerogels, and then incorporated silver nanowires (AgNWs) upon onside to fabricate the dual-function AgNWs/carbon aerogel. The resulting material inherits high porosity (99.3 %), high surface area (503.2 m2/g), low density (7.08 mg/cm3), and low thermal conductivity (18.2 mW·m-1·k-1 in the axial direction) to act as an ideal thermal insulator. The AgNWs coating side demonstrates low IR-emissivity (17.6 % at 7-14 μm) and the carbon aerogel side has high solar absorptivity (91.97 %). Moreover, the AgNWs/carbon aerogel shows Joule heating performance (∆T = 44.5 °C within 3 min at 5 V). The multi-heating modes enabling self-adaptable thermal comfortable under various harsh environment. Additionally, the material's breathability, permeability, and electromagnetic shielding characteristics also make it suitable candidate for advanced wearable textiles for PTM.

Stretchable and negative-Poisson-ratio porous metamaterials

Highly stretchable porous materials are promising for flexible electronics but their fabrication is a great challenge. Herein, several kinds of highly stretchable conductive porous elastomers with low or negative Poisson's ratios are achieved by uniaxial, biaxial, and triaxial hot-pressing strategies. The reduced graphene oxide/polymer nanocomposite elastomers with folded porous structures obtained by uniaxial hot pressing exhibit high stretchability up to 1200% strain. Furthermore, the meta-elastomers with reentrant porous structures combining high biaxial (or triaxial) stretchability and negative Poisson's ratios are achieved by biaxial (or triaxial) hot pressing. The resulting elastomer-based wearable strain sensors exhibit an ultrawide response range (0-1200%). The materials can be applied for smart thermal management and electromagnetic interference shielding, which are achieved by regulating the porous microstructures via stretching. This work provides a versatile strategy to highly stretchable and negative-Poisson-ratio porous materials with promising features for various applications such as flexible electronics, thermal management, electromagnetic shielding, and energy storage.

Biomimetic Bouligand chiral fibers array enables strong and superelastic ceramic aerogels

Ceramic aerogels are often used when thermal insulation materials are desired; however, they are still plagued by poor mechanical stability under thermal shock. Here, inspired by the dactyl clubs of mantis shrimp found in nature, which form by directed assembly into hierarchical, chiral and Bouligand (twisted plywood) structure exhibiting superior mechanical properties, we present a compositional and structural engineering strategy to develop strong, superelastic and fatigue resistance ceramic aerogels with chiral fibers array resembling Bouligand architecture. Benefiting from the stress dissipation, crack torsion and mechanical reinforcement of micro-/nano-scale Bouligand array, the tensile strength of these aerogels (170.38 MPa) is between one and two orders of magnitude greater than that of state-of-the-art nanofibrous aerogels. In addition, the developed aerogels feature low density and thermal conductivity, good compressive properties with rapid recovery from 80 % strain, and thermal stability up to 1200 °C, making them ideal for thermal insulation applications.

Multiscale Synergetic Bandgap/Structure Engineering in Semiconductor Nanofibrous Aerogels for Enhanced Solar Evaporation

Solar-driven interface evaporation has been identified as a sustainable seawater desalination and water purification technology. Nonetheless, the evaporation performance is still restricted by salt deposition and heat loss owing to weak solar spectrum absorption, tortuous channels, and limited plane area of conventional photothermal material. Herein, the semiconductor nanofibrous aerogels with a narrow bandgap, vertically aligned channels, and a conical architecture are constructed by the multiscale synergetic engineering strategy, encompassing bandgap engineering at the atomic scale and structure engineering at the nano-micro scale. As a proof-of-concept demonstration, a Co-doped MoS2 nanofibrous aerogel is synthesized, which exhibits the entire solar absorption, superhydrophilic, and excellent thermal insulation, achieving a net evaporation rate of 1.62 kg m-2 h-1 under 1 sun irradiation, as well as a synergistically efficient dye ion adsorption function. This work opens up new possibilities for the development of solar evaporators for practical applications in clean water production.

Ultrathin Aerogel Micro/Nanofiber Membranes with Hierarchical Cellular Architecture for High-Performance Warmth Retention

A low temperature environment poses significant challenges to the global economy and public health. However, the existing cold-protective materials still struggle with the trade-off between thickness and thermal resistance, resulting in poor thermal-wet comfort and limited personal cold protection performance. Here, a scalable strategy, based on electrospinning and solution casting, is developed to create aerogel micro/nanofiber membranes with a hierarchical cellular architecture by manipulating the phase separation of the charged jets and of the spreading casting solution. The integration of interconnected nanopores (30-60 nm), ultrafine fiber diameter, and high porosity, enables the aerogel micro/nanofiber membranes with lightweight, ultrathin thickness (∼0.5 mm), and superior warmth retention performance with ultralow thermal conductivity of 14.01 mW m-1 K-1. And the resultant membrane with customized semiclosed walls exhibits both striking wind resistance and satisfactory thermal-wet comfort (3.4 °C warmer than the cutting-edge thermal underwear). This work will inspire the design and development of high-performance fibrous materials for thermal management applications.

Engineering Covalent Heterointerface Enables Superelastic Amorphous SiC Meta-Aerogels

SiC is an exceptionally competitive material for porous ceramics owing to its excellent high-temperature mechanical stability. However, SiC porous ceramics suffer from serious structural damage and mechanical degradation under thermal shock due to the hard SiC microstructure and weak bonding networks. Here, we report a scalable interface-engineering protocol to reliably assemble flexible amorphous SiC nanofibers into lamellar cellular meta-aerogels by designing a covalent heterointerface. This approach allows the construction of a strong binding architecture within the resilient nanofiber skeleton network, thereby achieving structurally stable, mechanically robust, and durable SiC porous ceramics. The optimized amorphous SiC meta-aerogels (a-SiC MAs) exhibit the integrated properties of ultralight with a density of 4.84 mg cm-3, temperature-invariant superelastic, fatigue-resistant at low 5% permanent deformation after 1000 cycles of compression, and ultralow thermal conductivity (19 mW m-1 K-1). These characteristics provide a-SiC MAs potential application value in the thermal protection field.

Strong yet flexible ceramic aerogel

Ceramic aerogels are highly efficient, lightweight, and chemically stable thermal insulation materials but their application is hindered by their brittleness and low strength. Flexible nanostructure-assembled compressible aerogels have been developed to overcome the brittleness but they still show low strength, leading to insufficient load-bearing capacity. Here we designed and fabricated a laminated SiC-SiOx nanowire aerogel that exhibits reversible compressibility, recoverable buckling deformation, ductile tensile deformation, and simultaneous high strength of up to an order of magnitude larger than other ceramic aerogels. The aerogel also shows good thermal stability ranging from -196 °C in liquid nitrogen to above 1200 °C in butane blow torch, and good thermal insulation performance with a thermal conductivity of 39.3 ± 0.4 mW m-1 K-1. These integrated properties make the aerogel a promising candidate for mechanically robust and highly efficient flexible thermal insulation materials.

Inhibited Grain Growth Through Phase Transition Modulation Enables Excellent Mechanical Properties in Oxide Ceramic Nanofibers up to 1700 °C

Oxide ceramics are widely used as thermal protection materials due to their excellent structural properties and earth abundance. However, in extremely high-temperature environments (above 1500 °C), the explosive growth of grain size causes irreversible damage to the microstructure of oxide ceramics, thus exhibiting poor thermomechanical stability. This problem, which may lead to catastrophic accidents, remains a great challenge for oxide ceramic materials. Here, a novel strategy of phase transition modulation is proposed to control the grain growth at high temperatures in oxide ceramic nanofibers, realizing effective regulation of the crystalline forms as well as the size uniformity of primary grains, and thus suppressing the malignant growth of the grains. The resulting oxide ceramic nanofibers have excellent mechanical strength and flexibility, delivering an average tensile strength as high as 1.02 GPa after being exposed to 1700 °C for 30 min, and can withstand thousands of flexural cycles without obvious damage. This work may provide new insight into the development of advanced oxide ceramic materials that can serve in extremely high-temperature environments with long-term durability.

Bioinspired Thermochromic Textile Based on Robust Cellulose Aerogel Fiber for Self-Adaptive Thermal Management and Dynamic Labels

Aerogel fiber has emerged recently for incorporation in personal thermal management textiles due to its flexibility, scalability, and ultrahigh porosity, which allows the body to keep warm via thermal isolation without energy consumption. However, the functionalization and intellectualization of cellulose-based aerogel fibers have not yet been fully developed. Herein, we propose a biomimicking design inspired by polar bear and Siamese cat hair that combines porous cellulose aerogel fiber (CAF) with reversible thermochromic microcapsules to mimic biological sensory and adaptive thermoregulation functions. The produced CAF has a controllable pore structure, a large specific surface area (230 m2/g), and excellent mechanical strength (∼15 MPa). Low-temperature darkening microcapsules have been incorporated into the robust CAF to spontaneously adjust color by perceiving the ambient temperature. The functional aerogel fiber fabric achieves high thermal insulation and photothermal modulation simultaneously at temperatures below 18 °C. The temperature of the thermochromic fabric was higher by 6 °C than that of the sample without the microcapsules at a light intensity of 0.2 W/cm2. In addition, the aerogel fibers mixed with two types of thermochromic microcapsules exhibit three color switches with fast response, a color-control precision of 0.2 °C, and good cycling performance. This smart aerogel fibers hold great promise for self-adaptive thermal management, temperature indication, information transfer, and anticounterfeiting in textiles.

Advancing Nanofiber Research: Assessing Nonsolvent Contributions to Structure Using Coaxial Electrospinning

In this study, we explored the influence of molecular interactions and solvent evaporation kinetics on the formation of porous structures in electrospun nanofibers, utilizing polyacrylonitrile (PAN) and polystyrene (PS) as model polymers. The coaxial electrospinning technique was employed to control the injection of water and ethylene glycol (EG) as nonsolvents into polymer jets, demonstrating its potential as a powerful tool for manipulating phase separation processes and fabricating nanofibers with tailored properties. Our findings highlighted the critical role of intermolecular interactions between nonsolvents and polymers in governing phase separation and porous structure formation. Additionally, we observed that the size and polarity of nonsolvent molecules affected the phase separation process. Furthermore, solvent evaporation kinetics were found to significantly impact phase separation, as evidenced by less distinct porous structures when using a rapidly evaporating solvent like tetrahydrofuran (THF) instead of dimethylformamide (DMF). This work offers valuable insights into the intricate relationship between molecular interactions and solvent evaporation kinetics during electrospinning, providing guidance for researchers developing porous nanofibers with specific characteristics for various applications, including filtration, drug delivery, and tissue engineering.

Hierarchical triphase diffusion photoelectrodes for photoelectrochemical gas/liquid flow conversion

Photoelectrochemical device is a versatile platform for achieving various chemical transformations with solar energy. However, a grand challenge, originating from mass and electron transfer of triphase-reagents/products in gas phase, water/electrolyte/products in liquid phase and catalyst/photoelectrode in solid phase, largely limits its practical application. Here, we report the simulation-guided development of hierarchical triphase diffusion photoelectrodes, to improve mass transfer and ensure electron transfer for photoelectrochemical gas/liquid flow conversion. Semiconductor nanocrystals are controllably integrated within electrospun nanofiber-derived mat, overcoming inherent brittleness of semiconductors. The mechanically strong skeleton of free-standing mat, together with satisfactory photon absorption, electrical conductivity and hierarchical pores, enables the design of triphase diffusion photoelectrodes. Such a design allows photoelectrochemical gas/liquid conversion to be performed continuously in a flow cell. As a proof of concept, 16.6- and 4.0-fold enhancements are achieved for the production rate and product selectivity of methane conversion, respectively, with remarkable durability.

Enhancing quorum quenching media with 3D robust electrospinning coating: A novel biofouling control strategy for membrane bioreactors

Bacterial quorum quenching (QQ) is an effective strategy for controlling biofouling in membrane bioreactor (MBR) by interfering the releasing and degradation of signal molecules during quorum sensing (QS) process. However, due to the framework feature of QQ media, the maintenance of QQ activity and the restriction of mass transfer threshold, it has been difficult to design a more stable and better performing structure in a long period of time. In this research, electrospun fiber coated hydrogel QQ beads (QQ-ECHB) were fabricated by using electrospun nanofiber coated hydrogel to strengthen layers of QQ carriers for the first time. The robust porous PVDF 3D nanofiber membrane was coated on the surface of millimeter-scale QQ hydrogel beads. Biocompatible hydrogel entrapping quorum quenching bacteria (sp.BH4) was employed as the core of the QQ-ECHB. In MBR with the addition of QQ-ECHB, the time to reach transmembrane pressure (TMP) of 40 kPa was 4 times longer than conventional MBR. The robust coating and porous microstructure of QQ-ECHB contributed to keeping a lasting QQ activity and stable physical washing effect at a very low dosage (10g beads/5L MBR). Physical stability and environmental-tolerance tests also verified that the carrier can maintain the structural strength and keep the core bacteria stable when suffering long-term cyclic compression and great fluctuations in sewage quality.

Unveiling the Mechanism of the in Situ Formation of 3D Fiber Macroassemblies with Controlled Properties

Electrospinning technique is well-known for the generation of different fibers. While it is a "simple" technique, it lies in the fact that the fibers are typically produced in the form of densely packed two-dimensional (2D) mats with limited thickness, shape, and porosity. The highly demanded three-dimensional (3D) fiber assemblies have been explored by time-consuming postprocessing and/or complex setup modifications. Here, we use a classic electrospinning setup to directly produce 3D fiber macrostructures only by modulating the spinning solution. Increasing solution conductivity modifies electrodynamic jet behavior and fiber assembling process; both are observed in situ using a high-speed camera. More viscous solutions render thicker fibers that own enhanced mechanical stiffness as examined by finite element analysis. We reveal the correlation between the universal solution parameters and the dimensionality of fiber assemblies, thereof, enlightening the design of more "3D spinnable" solutions that are compatible with any commercial electrospinning equipment. After a calcination step, ultralightweight ceramic fiber assemblies are generated. These inexpensive materials can clean up exceptionally large fractions of oil spillages and provide high-performance thermal insulation. This work would drive the development and scale-up production of next-generation 3D fiber materials for engineering, biomedical, and environmental applications.

Fabrication and Applications of Ceramic-Based Nanofiber Materials Service in High-Temperature Harsh Conditions—A Review

Ceramic-based nanofiber materials have attracted attention due to their high-temperature resistance, oxidation resistance, chemical stability, and excellent mechanical performance, such as flexibility, tensile, and compression, which endow them with promising application prospects for filtration, water treatment, sound insulation, thermal insulation, etc. According to the above advantages, we, therefore, reviewed the ceramic-based nanofiber materials from the perspectives of components, microstructure, and applications to provide a systematical introduction to ceramic-based nanofiber materials as so-called blankets or aerogels, as well as their applications for thermal insulation, catalysis, and water treatment. We hope that this review will provide some necessary suggestions for further research on ceramic-based nanomaterials.