A Highly Compressible and Stretchable Carbon Spring for Smart Vibration and Magnetism Sensors

Advances in Ice-Templated Graphene Aerogels: Fabrication, Properties, and Applications

Graphene has been one of the most widely explored two-dimensional (2D) assemblies due to its outstanding mechanical, electrical, and thermal properties resulting from its unique characteristics of high anisotropy and strong carbon-carbon bonds. Aerogels, characterized by their ultralow density and ultrahigh specific surface area, stand out as leading porous materials. Therefore, the integration of graphene and aerogels would boost the development of multifunctional porous materials. Among the various methods for the fabrication of aerogels, ice-templating has received significant interest due to its ecofriendly nature as a physical process, its broad applicability across material systems, and its proficiency in constructing abundant structures for multifunctionalities. Consequently, ice-templating has become a prevalent technique for the efficient assembly of graphene nanosheets into aerogels with the inherited properties of graphene, the multifunctionality derived from diverse constituents, and the well-controlled architecture. In this review, we systematically summarize the development and progress of ice-templated graphene-based aerogels. Initially, we introduce the fabrication process of these aerogels, elaborating each step from precursor preparation to freezing, drying, and post-treatment. Subsequently, we demonstrate the multifunctional applications of ice-templated graphene aerogels with various macroarchitectures and microstructures. Finally, this review concludes with a straightforward summary, highlighting the challenges and opportunities associated with the ice-templated fabrication of graphene-based aerogels. This systematic review of graphene aerogels aims to offer new insights into the design and ice-templated fabrication of innovative aerogels with multiscale architecture and multifunctionalities, which are crucial for a variety of engineering applications.

Ultra-Stiff yet Super-Elastic Graphene Aerogels by Topological Cellular Hierarchy

Lightweight cellular materials with high stiffness and excellent recoverability are critically important in structural engineering applications, but the intrinsic conflict between these two properties presents a significant challenge. Here, a topological cellular hierarchy is presented, designed to fabricate ultra-stiff (>10 MPa modulus) yet super-elastic (>90% recoverable strain) graphene aerogels. This topological cellular hierarchy, composed of massive corrugated pores and nanowalls, is designed to carry high loads through predominantly reversible buckling within the honeycomb framework. The compressive modulus of the as-prepared graphene aerogel is nearly twice that of conventional graphene aerogel. This high-stiff graphene aerogel also exhibits exceptional mechanical recoverability, achieving up to 60% strain recovery over 10 000 fatigue cycles without significant structural failure, outperforming most previously reported porous lattices and monoliths. It is further demonstrated that this graphene aerogel exhibits superior energy dissipation and anti-fatigue dynamic impact properties, with an energy absorption capacity nearly an order of magnitude greater than that of conventional aerogels. These exceptional properties of the topological cellular graphene aerogel open new avenues for high-energy bullet protection, offering great promise for the development of lightweight, armor-like protective materials in transportation and aerospace applications.

Functional Carbon Springs Enabled Dynamic Tunable Microwave Absorption and Thermal Insulation

Electromagnetic (EM) wave pollution and thermal damage pose serious hazards to delicate instruments. Functional aerogels offer a promising solution by mitigating EM interference and isolating heat. However, most of these materials struggle to balance thermal protection with microwave absorption (MA) efficiency due to a previously unidentified conflict between the optimizing strategies of the two properties. Herein, this study reports a solution involving the design of a carbon-based aerogel called functional carbon spring (FCS). Its unique long-range lamellar multi-arch microstructure enables tunable MA performance and excellent thermal insulation capability. Adjusting compression strain from 0% to 50%, the adjustable effective absorption bandwidth (EAB) spans up to 13.4 GHz, covering 84% of the measured frequency spectrum. Notably, at 75% strain, the EAB drops to 0 GHz, demonstrating a novel "on-off" switchability for MA performance. Its ultralow vertical thermal conductivity (12.7 mW m-1 K-1) and unique anisotropic heat transfer mechanism endow FCS with superior thermal protection effectiveness. Numerical simulations demonstrate that FCS outperforms common honeycomb structures and isotropic porous aerogels in thermal management. Furthermore, an "electromagnetic-thermal" dual-protection material database is established, which intuitively demonstrates the superiority of the solution. This work contributes to the advancement of multifunctional MA materials with significant potential for practical applications.

Vertical-Channel Cathode Host Enables Rapid Deposition Kinetics toward High-Areal-Capacity Sodium-Chlorine Batteries

Rechargeable sodium chloride (Na-Cl2) batteries have emerged as promising alternatives for next-generation energy storage due to their superior energy density and sodium abundance. However, their practical applications are hindered by the sluggish chlorine cathode kinetics related to the aggregation of NaCl and its difficult transformation into Cl2. Herein, the study, for the first time from the perspective of electrode level in Na-Cl2 batteries, proposes a free-standing carbon cathode host with customized vertical channels to facilitate the SOCl2 transport and regulate the NaCl deposition. Accordingly, electrode kinetics are significantly enhanced, and the deposited NaCl is distributed evenly across the whole electrode, avoiding the blockage of pores in the carbon host, and facilitating its oxidation to Cl2. With this low-polarization cathode, the Na-Cl2 batteries can deliver a practically high areal capacity approaching 4 mAh cm-2 and a long cycle life of over 170 cycles. This work demonstrates the significance of pore engineering in electrodes for mediating chlorine conversion kinetics in rechargeable alkali-metal-Cl2 batteries.

Enhancing Interface Connectivity for Multifunctional Magnetic Carbon Aerogels: An In Situ Growth Strategy of Metal-Organic Frameworks on Cellulose Nanofibrils

Improving interface connectivity of magnetic nanoparticles in carbon aerogels is crucial, yet challenging for assembling lightweight, elastic, high-performance, and multifunctional carbon architectures. Here, an in situ growth strategy to achieve high dispersion of metal-organic frameworks (MOFs)-anchored cellulose nanofibrils to enhance the interface connection quality is proposed. Followed by a facile freeze-casting and carbonization treatment, sustainable biomimetic porous carbon aerogels with highly dispersed and closely connected MOF-derived magnetic nano-capsules are fabricated. Thanks to the tight interface bonding of nano-capsule microstructure, these aerogels showcase remarkable mechanical robustness and flexibility, tunable electrical conductivity and magnetization intensity, and excellent electromagnetic wave absorption performance. Achieving a reflection loss of -70.8 dB and a broadened effective absorption bandwidth of 6.0 GHz at a filling fraction of merely 2.2 wt.%, leading to a specific reflection loss of -1450 dB mm-1, surpassing all carbon-based aerogel absorbers so far reported. Meanwhile, the aerogel manifests high magnetic sensing sensibility and excellent thermal insulation. This work provides an extendable in situ growth strategy for synthesizing MOF-modified cellulose nanofibril structures, thereby promoting the development of high-value-added multifunctional magnetic carbon aerogels for applications in electromagnetic compatibility and protection, thermal management, diversified sensing, Internet of Things devices, and aerospace.

Bottom-Up Film-to-Bulk Assembly Toward Bioinspired Bulk Structural Nanocomposites

Biological materials, although composed of meager minerals and biopolymers, often exhibit amazing mechanical properties far beyond their components due to hierarchically ordered structures. Understanding their structure-properties relationships and replicating them into artificial materials would boost the development of bulk structural nanocomposites. Layered microstructure widely exists in biological materials, serving as the fundamental structure in nanosheet-based nacres and nanofiber-based Bouligand tissues, and implying superior mechanical properties. High-efficient and scalable fabrication of bioinspired bulk structural nanocomposites with precise layered microstructure is therefore important yet remains difficult. Here, one straightforward bottom-up film-to-bulk assembly strategy is focused for fabricating bioinspired layered bulk structural nanocomposites. The bottom-up assembly strategy inherently offers a methodology for precise construction of bioinspired layered microstructure in bulk form, availability for fabrication of bioinspired bulk structural nanocomposites with large sizes and complex shapes, possibility for design of multiscale interfaces, feasibility for manipulation of diverse heterogeneities. Not limited to discussing what has been achieved by using the current bottom-up film-to-bulk assembly strategy, it is also envisioned how to promote such an assembly strategy to better benefit the development of bioinspired bulk structural nanocomposites. Compared to other assembly strategies, the highlighted strategy provides great opportunities for creating bioinspired bulk structural nanocomposites on demand.

Accurate additive manufacturing of lightweight and elastic carbons using plastic precursors

Despite groundbreaking advances in the additive manufacturing of polymers, metals, and ceramics, scaled and accurate production of structured carbons remains largely underdeveloped. This work reports a simple method to produce complex carbon materials with very low dimensional shrinkage from printed to carbonized state (less than 4%), using commercially available polypropylene precursors and a fused filament fabrication-based process. The control of macrostructural retention is enabled by the inclusion of fiber fillers regardless of the crosslinking degree of the polypropylene matrix, providing a significant advantage to directly control the density, porosity, and mechanical properties of 3D printed carbons. Using the same printed plastic precursors, different mechanical responses of derived carbons can be obtained, notably from stiff to highly compressible. This report harnesses the power of additive manufacturing for producing carbons with accurately controlled structure and properties, while enabling great opportunities for various applications.

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.

Functional Janus structured liquids and aerogels

Janus structures have unique properties due to their distinct functionalities on opposing faces, but have yet to be realized with flowing liquids. We demonstrate such Janus liquids with a customizable distribution of nanoparticles (NPs) throughout their structures by joining two aqueous streams of NP dispersions in an apolar liquid. Using this anisotropic integration platform, different magnetic, conductive, or non-responsive NPs can be spatially confined to opposite sides of the original interface using magnetic graphene oxide (mGO)/GO, Ti3C2Tx/GO, or GO suspensions. The resultant Janus liquids can be used as templates for versatile, responsive, and mechanically robust aerogels suitable for piezoresistive sensing, human motion monitoring, and electromagnetic interference (EMI) shielding with a tuned absorption mechanism. The EMI shields outperform their current counterparts in terms of wave absorption, i.e., SET ≈ 51 dB, SER ≈ 0.4 dB, and A = 0.91, due to their high porosity ranging from micro- to macro-scales along with non-interfering magnetic and conductive networks imparted by the Janus architecture.

Direct Synthesis of Elastic and Stretchable Hierarchical Structured Fiber and Graphene-Based Sponges for Noise Reduction

Noise pollution, as one of the three major pollutants in the world, has become a great burden on people's health and the global economy. Most present noise absorbers suffer large weight and inevitable compromise between good low-frequency (usually <1000 Hz) and high-frequency (typically >1000 Hz) noise reduction performance. This study presents a scalable strategy to directly synthesize ultrafine fiber sponges with ultrathin graphene-based vibrators by the synchronous occurrence of humidity-assisted electrospinning and electrospraying. The unique physical entanglements between reduced graphene oxide (rGO) nanosheets and ultrafine fibers endow hierarchical vibration structured fiber sponges (VSFSs) with excellent mechanical properties, which could withstand large shear strain (60%) and tensile stress (6000 times its weight) without damage and almost have no plastic deformation after 1000 compressions. Attribute to the vibration effect of ultrathin graphene-based vibrators and the viscous friction effect of porous fiber networks, the VSFSs achieve both good low-frequency (absorption coefficient of 0.98 in 680 Hz) and high-frequency sound absorption (absorption coefficients above 0.8 in 2000-6300 Hz) simultaneously. Furthermore, the noise reduction coefficient (NRC) of lightweight VSFSs (thickness of 30 mm) reaches 0.63, which could reduce high decibel noise by 24.4 dB, providing potential solutions for developing ideal noise-absorbing materials.

Superflexible Artificial Soft Wood

Soft woods have attracted enormous interest due to their anisotropic cellular microstructure and unique flexibility. The conventional wood-like materials are usually subject to the conflict between the superflexibility and robustness. Inspired by the synergistic compositions of soft suberin and rigid lignin of cork wood which has good flexibility and mechanical robustness, an artificial soft wood is reported by freeze-casting the soft-in-rigid (rubber-in-resin) emulsions, where the carboxy nitrile rubber confers softness and rigid melamine resin provides stiffness. The subsequent thermal curing induces micro-scale phase inversion and leads to a continuous soft phase strengthened by interspersed rigid ingredients. The unique configuration ensures crack resistance, structural robustness and superb flexibility, including wide-angle bending, twisting, and stretching abilities in various directions, as well as excellent fatigue resistance and high strength, overwhelming the natural soft wood and most wood-inspired materials. This superflexible artificial soft wood represents a promising substrate for bending-insensitive stress sensors.

Preparation of High-k Polymeric Composites Based on Low-k Boron Nitride Nanosheets with High-Connectivity Lamellar Structure

Typically, the basic method to enhance the dielectric response of polymer-based composites is to fill giant dielectric ceramic fillers, such as BaTiO₃ and CaCu₃Ti₄O₁₂, into the polymer matrix. Here, by using low-k boron nitride (BN) with well-controlled microstructure and surface, we successfully prepared a high-k polymeric composite, where the improvement in the dielectric constant of the composite even exceeds that of composites containing BaTiO₃ and CaCu₃Ti₄O₁₂ particles at the same weight percent. First, a lamellar boron nitride nanosheet (BNNS) aerogel was prepared by bidirectional freezing and freeze drying, respectively, and then the aerogel was calcined at 1000 °C to obtain the lamellar BNNS skeleton with some hydroxyl groups. Finally, the epoxy resin (EP) was vacuum impregnated into the BNNS skeleton and cured inside to prepare the lamellar-structured BNNSs/EP (LBE) composites. Interestingly, the dielectric constants of LBE with a 10 wt % BNNS content reached 8.5 at 10³ Hz, which was higher by 2.7 times than that of pure EP. The experimental data and the finite element simulations suggested that the increased dielectric constants of LBE resulted from the combination of two factors, namely, the lamellar microstructure and the hydroxyl groups. The stacking of the BNNS phase into a highly connected lamellar skeleton significantly increased the internal electric field and the polarization intensity, while the introduction of hydroxyl groups on the BNNS surface further improved the polarization of the composite, resulting in a significant increase in the dielectric constant of the LBE. This work provides a new strategy for improving the dielectric constant through the microstructure design of composites.

Recent Advancements in Physiological, Biochemical, and Multimodal Sensors Based on Flexible Substrates: Strategies, Technologies, and Integrations

Flexible wearable devices have been widely used in biomedical applications, the Internet of Things, and other fields, attracting the attention of many researchers. The physiological and biochemical information on the human body reflects various health states, providing essential data for human health examination and personalized medical treatment. Meanwhile, physiological and biochemical information reveals the moving state and position of the human body, and it is the data basis for realizing human-computer interactions. Flexible wearable physiological and biochemical sensors provide real-time, human-friendly monitoring because of their light weight, wearability, and high flexibility. This paper reviews the latest advancements, strategies, and technologies of flexibly wearable physiological and biochemical sensors (pressure, strain, humidity, saliva, sweat, and tears). Next, we systematically summarize the integration principles of flexible physiological and biochemical sensors with the current research progress. Finally, important directions and challenges of physiological, biochemical, and multimodal sensors are proposed to realize their potential applications for human movement, health monitoring, and personalized medicine.

Ultra-stretchable graphene aerogels at ultralow temperatures

Graphene aerogels (GAs) possess workable deformation and sensing properties at extreme temperatures. However, their poor tensile properties have restricted their applications in stretchable electronic devices, smart soft robots, and aerospace. Herein, an ultra-stretchable and elastic graphene aerogel with record elongation from -95% to 400% was achieved by constructing a highly crimped and crosslinked graphene network using a microbubble-filled GA precursor by a simple compress-annealing process. This conductive aerogel with near zero Poisson's ratio showed rubber-like but temperature-invariant elasticity from 196.5 °C to 300 °C, and special strain insensitivity from 50% to 400% tensile strain and high sensitivity below 50% tensile strain. Therefore, it can be used as a highly stretchable but strain-insensitive conductor under extreme environments, in which these polymer-based stretchable conductive materials are not workable. Moreover, this work provides new thoughts on constructing inorganic ultra-stretchable materials.

Bioinspired Gradient Stretchable Aerogels for Ultrabroad-Range-Response Pressure-Sensitive Wearable Electronics and High-Efficient Separators

Broad-range-response pressure-sensitive wearable electronics are urgently needed but their preparation remains a challenge. Herein, we report unprecedented bioinspired wearable electronics based on stretchable and superelastic reduced graphene oxide/polyurethane nanocomposite aerogels with gradient porous structures by a sol-gel/hot pressing/freeze casting/ambient pressure drying strategy. The gradient structure with a hot-pressed layer promotes strain transfer and resistance variation under high pressures, leading to an ultrabroad detection range of 1 Pa-12.6 MPa, one of the broadest ranges ever reported. They can withstand 10 000 compression cycles under 1 MPa, which can't be achieved by traditional flexible pressure sensors. They can be applied for broad-range-response electronic skins and monitoring various physical signals/motions and ultrahigh pressures of automobile tires. Moreover, the gradient aerogels can be used as high-efficient gradient separators for water purification.

Nacre-Mimetic Hierarchical Architecture in Polyborosiloxane Composites for Synergistically Enhanced Impact Resistance and Ultra-Efficient Electromagnetic Interference Shielding

Pervasive mechanical impact is growing requirement for advanced high-performance protective materials, while the electromagnetic interference (EMI) confers severe risk to human health and equipment operation. Bioinspired structural composites achieving outstanding safeguards against a single threat have been developed, whereas the synergistic implementation of impact/EMI coupling protection remains a challenge. This work proposes the concept of nacre-mimetic hierarchical composite duplicating the "brick-and-mortar" arrangement, which consists of freeze-drying constructed chitosan/MXene lamellar architecture skeleton embedded in a shear stiffening polyborosiloxane matrix. The resulting composite effectively attenuates the impact force of 85.9%-92.8% with extraordinary energy dissipation capacity, in the coordinative manner of strain-rate enhancement, structural densification, lamella dislocation and crack propagation. Attributed to the alternate laminated structure promoting the reflection loss of electromagnetic waves, it demonstrates an ultraefficient EMI shielding effectiveness of 47.2-71.8 dB within extremely low MXene loadings of 1.1-1.3 wt %. Furthermore, it serves favorably in impact monitoring and wireless alarm systems and accomplishes performance optimization through the combination of multiple biomimetic strategies. In conclusion, this function-integrated structural composite is shown to be a competitive candidate for sophisticated environments by resisting impact damage and EMI hazards.

Superelastic, Highly Conductive, Superhydrophobic, and Powerful Electromagnetic Shielding Hybrid Aerogels Built from Orthogonal Graphene and Boron Nitride Nanoribbons

Three-dimensional (3D) elastic aerogels enable diverse applications but are usually restricted by their low thermal and electrical transfer efficiency. Here, we demonstrate a strategy for fabricating the highly thermally and electrically conductive aerogels using hybrid carbon/ceramic structural units made of hexagonal boron nitride nanoribbons (BNNRs) with in situ-grown orthogonally structured graphene (OSG). High-aspect-ratio BNNRs are first interconnected into a 3D elastic and thermally conductive skeleton, in which the horizontal graphene layers of OSG provide additional hyperchannels for electron and phonon conduction, and the vertical graphene sheets of OSG greatly improve surface roughness and charge polarization ability of the entire skeleton. The resulting OSG/BNNR hybrid aerogel exhibits very high thermal and electrical conductivity (up to 7.84 W m^-1 K^-1 and 340 S m^-1, respectively) at a low density of 45.8 mg cm^-3, which should prove to be vastly advantageous as compared to the reported carbonic and/or ceramic aerogels. Moreover, the hybrid aerogel possesses integrated properties of wide temperature-invariant superelasticity (from -196 to 600 °C), low-voltage-driven Joule heating (up to 42-134 °C at 1-4 V), strong hydrophobicity (contact angel of up to 156.1°), and powerful broadband electromagnetic interference (EMI) shielding effectiveness (reaching 70.9 dB at 2 mm thickness), all of which can maintain very well under repeated mechanical deformations and long-term immersion in strong acid or alkali solution. Using these extraordinary comprehensive properties, we prove the great potential of OSG/BNNR hybrid aerogel in wearable electronics for regulating body temperature, proofing water and pollution, removing ice, and protecting human health against EMI.

Sustainable-Macromolecule-Assisted Preparation of Cross-linked, Ultralight, Flexible Graphene Aerogel Sensors toward Low-Frequency Strain/Pressure to High-Frequency Vibration Sensing

Ultralight and highly flexible aerogel sensors, composed of reduced graphene oxide cross-linked by sustainable-macromolecule-derived carbon, are prepared via facile freeze-drying and thermal annealing. The synergistic combination of cross-linked graphene nanosheets and micrometer-sized honeycomb pores gives rise to the exceptional properties of the aerogels, including superior compressibility and resilience, good mechanical strength and durability, satisfactory fire-resistance, and outstanding electromechanical sensing performances. The corresponding aerogel sensors, operated at an ultralow voltage of 0.2 V, can efficiently respond to a wide range of strains (0.1-80%) and pressures (13-2750 Pa) even at temperatures beyond 300 °C. Moreover, the ultrahigh-pressure sensitivity of 10 kPa^-1 and excellent sensing stability and durability are accomplished. Strikingly, the aerogel sensors can also sense the vibration signals with ultrahigh frequencies of up to 4000 Hz for >1 000 000 cycles, significantly outperforming those of other sensors. These enable successful demonstration of the exceptional performance of the cross-linked graphene-based biomimetic aerogels for sensitive monitoring of mechanical signals, e.g., acting as wearable devices for monitoring human motions, and for nondestructive monitoring of cracks on engineering structures, showing the great potential of the aerogel sensors as next-generation electronics.

Non-Hookean Droplet Spring for Enhancing Hydropower Harvest

Nonlinear elastic materials are significant for engineering and micromechanics. Droplets with the merits of easy-accessibility, diversity, and energy-absorption capability exhibit a variety of non-Hookean elastic behaviors. Herein, benefiting from the confinement of heterogeneous-wettable parallel plates, the non-Hookean mechanics of the droplet-based spring are systematically investigated. Experimental results and theoretical analysis reveal that the force generated by the spring varies nonlinearly with its deformation, and a force model is accordingly built to depict the mechanics of springs with different sized/numbered droplets and confined by different wettability patterns. Importantly, for the droplet-based spring, the droplet-plate contact area expands nonlinearly with the pressing force, which is employed to optimize the output performance of the droplet-based triboelectric nanogenerator to 226% compared with the control test. This finding deepens the understanding of the non-Hookean behavior of droplet-based springs, and sheds light on applications in energy harvesting, micromechanics, and miniature optic/electric devices.

Wires with Continuous Sabal Leaf-Patterned Micropores Constructed by Freeze Printing for a Wearable Sensor Responsible to Multiple Deformations

The design of porous structure in wearable sensors is very important for the detection of mechanical signals. However, it remains challenging to construct a porous structure capable of detecting all kinds of mechanical signals. Here, round wire with long-range orientated micropores (RW-LOM) is fabricated by a newly established freeze printing technique and constructed into a wearable sensor by the incorporation of carbon nanotubes and polydimethylsiloxane. The Sabal leaf-like lamellar structure in RW-LOM is realized and can be tuned by the proper coordination of slurry concentration and the printing parameters. The fine structures in RW-LOM allow the wearable sensor to detect compression, stretching, twisting, and bending with a high sensitivity, stability, and broad detecting range. This work not only provides a wearable sensor with high stability and high sensitivity but also establishes a technique to construct porous wires that could find applications in the fields like intelligent industry and healthcare.

All-Ceramic and Elastic Aerogels with Nanofibrous-Granular Binary Synergistic Structure for Thermal Superinsulation

High-performance thermally insulating ceramic materials with robust mechanical properties, high-temperature resistance, and excellent thermal insulation characteristics are highly desirable for thermal management systems under extreme conditions. However, the large-scale application of traditional ceramic granular aerogels is still limited by their brittleness and stiff nature, while ceramic fibrous aerogels often display high thermal conductivity. To meet the above requirements, in this study, ceramic nanofibrous-granular composite aerogels with lamellar multiarch cellular structure and leaf-like fibrous-granular binary networks are designed and fabricated. The resulting composite aerogels possess ultralow weight, superelasticity with recoverable compression strain up to 80%, and large mechanical strength. Furthermore, excellent fatigue resistance with 1.2% plastic deformation after 1000 cyclic compressions, temperature-invariant dynamic mechanical stability from -100 to 500 °C, and an operational temperature range from -196 to 1100 °C are successfully achieved in the proposed composites. The nanosized silica granular aerogels are assembled into a leaf-like shape and wrapped around the fibrous cell walls, endowing low thermal conductivity (0.024 W m^-1 K^-1) as well as favorable high-temperature thermal superinsulation properties. Benefiting from the favorable compatibility, the present strategy for nanofiber-granular composite ceramic aerogels provides a dominant route to produce thermally insulated and mechanically robust composite cellular materials for use in harsh environments.

Enhancing the magnetic response on polycrystalline nanoframes through mechanical deformation

The mechanical and magnetic properties of polycrystalline nanoframes were investigated using atomistic molecular dynamics and micromagnetic simulations. The magneto-mechanical response of Fe hollow-like nanocubes was addressed by uniaxial compression carried out by nanoindentation. Our results show that the deformation of a nanoframe is dominated at lower strains by the compression of the nanostructure due to filament bending. This leads to the nanoframe twisting perpendicular to the indentation direction for larger indentation depths. Bending and twisting reduce stress concentration and, at the same time, increase coercivity. This unexpected increase of the coercivity occurs because the mechanical deformation changes the cubic shape of the nanoframe, which in turn drives the system to more stable magnetic states. A coercivity increase of almost 100 mT is found for strains close to 0.03, which are within the elastic regime of the Fe nanoframe. Coercivity then decreases at larger strains. However, in all cases, the coercivity is higher than for the undeformed nanoframe. These results can help in the design of new magnetic devices where mechanical deformation can be used as a primary tool to tailor the magnetic response on nanoscale solids.

Mechanically Tunable Spongy Graphene/Cellulose Nanocrystals Hybrid Aerogel by Atmospheric Drying and Its Adsorption Applications

For expanding applications of spongy graphene aerogels (GAs) cost-effectively, we report a marriage of the two-step hydrothermal reduction and atmospheric drying method to fabricate a spongy CNC-graphene aerogel (CNG) with oil/water selectivity and tunable mechanical strength by a low-cost and straightforward approach. The reduced graphene oxide (rGO) with CNC by the ice-templated method can give rise to forming the hierarchical structure of hybrid GAs within the PUS network. Meanwhile, the fractured structure of PUS with a pre-compressive step arouses more versatility and durability, involving its selective and high-volume absorbability (up to 143%). The enhanced elastic modulus and more significant swelling effect than pure sponge materials give it a high potential for durable wastewater treatment.