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Aerogels were listed among the top ten emerging technologies in chemistry by IUPAC in 2022. Their record-breaking properties sparked the emergence of a thriving insulation market, but solutions are sought to promote additional applications. A 3D assembly process based on direct ink writing of "aerogel-in-aerogel" nanocomposites is presented. The printed polyimide-silica aerogels are non-brittle (E = 6.7 MPa) with a super-insulating thermal conductivity (20.3 mW m(-1) K-1) and high thermal stability (T-5wt% 447 degrees C). In addition, they display excellent low-loss dielectric properties and microwave transmission over all relevant communication bands and can be functionalized for electromagnetic interference (EMI) shielding. The high shape-fidelity printing, combined with laser-induced etching of thermally conductive graphene layers, enable precise thermal management for portable electronics or maintain an extreme temperature gradient (-40 to +50 degrees C) across a millimeter-scale partition., Advanced Materials Technologies, ISSN:2365-709X

Targeting for flexible, broadband ultrasound sensors, a new breed of nanographene platelet (NGP)/polyimide (PI) film is inkjet printed with morphologically optimized NGP/poly (amic acid) hybrid-based nanocomposite ink. The ink is produced with high-shear liquid phase exfoliation from inexpensive bulk graphite, manifesting good printability and high graphene concentration as high as 13.1 mg mL−1. Featuring an ultra-thin thickness (∼1 μm only), the inkjet-printed NGP/PI film sensor is demonstrated to possess excellent thermal stability and high adhesive strength reaching the American Society for Testing and Materials 5B level. The highly uniform and consolidated NGP/PI nanostructure in the sensor enables the formation of π-π interaction between NGPs and PI polymer matrix, and the quantum tunneling effect is triggered among NGPs when ultrasound traverses the sensor. This sensing mechanism endows the NGP/PI sensor with good sensitivity, fidelity and accuracy, showing comparable performance as prevailing commercial ultrasound sensors such as piezoelectric sensors. The film sensor has a proven gauge factor as high as 739, when sensing ultrasound at 175 kHz, and an ultrabroad responsive spectrum up to 1.6 MHz.

The development of flexible composites based on the transition metal carbides/nitrides (MXenes) is gaining popularity because of MXenes' high application potentials for electromagnetic interference (EMI) shields. Here, we prepare a new type of ultraflexible composite films composed of "trashed" MXene sediment (MS) and waterborne polyurethane using a simple, facile solution casting approach. In addition to the outstanding mechanical strength and electrical conductivity, an extremely wide-range of MS contents can be achieved for the composites, resulting in EMI shielding effectiveness (SE) that may be controlled over a wide range. The X-band EMI SE of the flexible, low-density composites containing 70 wt % MS reaches 45.3 dB at a thickness of merely 0.51 mm. Moreover, the SE values of more than 34.5 dB in the ultrabroadband gigahertz frequency range including X-band, P-band, K-band, and R-band, are accomplished for the thin composites. Furthermore, the MS/WPU composite films show excellent electrothermal and photothermal performance, demonstrating the multifunctionalities of the MS-based EMI shields. Combined with the cost-efficient, sustainable, and scalable preparation approach, the ultraflexible, multifunctional composites from "trashed MXene" show great potentials for next-generation electronics. This work also opens a new avenue for the creation of innovative, high-performance, multifunctional flexible composites.

Lightweight, thin, large-area, and ultraflexible chemical-cross-linked MXene/superaligned carbon nanotube composite films with a bicontinuous structure are manufactured. The films exhibit high mechanical strength, good electrical conductivity, hydrophobicity, and oxidation stability, as well as wearable multifunctionalities involving electromagnetic interference (EMI) shielding, electrothermal conversion, and photothermal antibacterial performance. An X-band EMI shielding effectiveness (SE) of 24 to 70 dB at the thickness of 8 to 28 μm and an SE of more than 60 dB in ultrabroadband frequency range of 8.2-40 GHz are accomplished. A surface specific SE of 122 368 dB·cm

To avoid excessive usage of antibiotics and antimicrobial agents, smart wound dressings permitting controlled drug release for treatment of bacterial infections are highly desired. In search of a sensitive stimulus to activate drug release under physiological conditions, we found that the glass transition temperature (

Strong electromagnetic (EM) response at low thickness is urgently required to address the emerging EM radiation pollution. Among numerous methods to achieve electromagnetic response at low thickness, interface construction exhibits some advantages for the combination of numerous dissipation mechanisms. Here, ternary Mo-Ni2P/rGO absorbers with multiple interfaces are designed via the phosphating treatment at a certain temperature. The constructed heterojunctions can efficiently exploit the high-conjunction of Ni2P and rGO and the interactions between different dielectric media (metal/semiconductor/conductor) for excellent electrical conductivity, abundant interfacial polarizations, and rational combination of different loss materials. As the phosphating temperature increases from 600 to 800 °C, the Mo-Ni2P/rGO-800 sample exhibits excellent microwave absorption performance, where the reflection loss (RL) value is −35.43 dB, and the effective bandwidth reaches 3.48 GHz at only 1.20 mm. This study proposes a simple method to enhance the microwave absorption performance at low thickness based on the construction of heterojunction structures. Moreover, an insight into the role of integrating different loss mechanisms in achieving high-efficiency EM wave absorbers has been fulfilled.

Metal nanofibers with excellent electrical conductivity and superior mechanical flexibility have great potentials for fabrication of lightweight, flexible, and high-performance electromagnetic interference (EMI) shielding architectures. The weak interactions and large contact resistance among the wires, however, hinder their assembly into robust and high-performance EMI shielding monoliths. In this work, we used low fractions of polymers to assist the construction of lightweight, flexible, and highly conductive silver nanowire (AgNW) cellular monoliths with significantly enhanced mechanical strength and EMI shielding effectiveness (SE). The normalized surface specific SE of our AgNW-based cellular monoliths can reach up to 20522 dB·cm2/g, outracing that of most shielding materials ever reported. Moreover, this robust conductive framework enabled the successful fabrication of hydrophobic, ultraflexible, and highly stretchable aerogel/polymer composites with outstanding EMI SE even at an extremely low AgNW content. Thus, this work demonstrated a facile and efficient strategy for assembling metal nanofiber-based functional high-performance EMI shielding architectures.

Lightweight nanostructured aerogels have attracted more and more attention for addressing emergency electromagnetic radiation or interference thanks to their high and controllable electromagnetic interference (EMI) shielding performances arising from cellular structure and nanoscale building blocks thereof including their synergistic interactions. Efficient design and utilization of cellular morphologies and functional nanomaterials for higher EMI shielding effectiveness (SE) at lower material consumption is always the research trend yet remains challenging. Here, we employed thin-dimension cellulose nanofibrils (CNFs) for assisting in building ultralow-density, robust, and highly flexible nanostructured aerogels with orientated biomimetic hybrid cell walls. The ultrathin cell walls with conductive nanomaterial including carbon nanotubes, AgNWs, and MXene as “bricks” bonded by nanoscale CNF “mortar” maintain high electrical conductivity of pristine nanomaterials and enhance significantly the mechanical strength of hybrid aerogels. High conductivity and introduced interfaces between nanomaterials and CNFs lead to high intrinsic shielding ability of cell walls, which can be amplified by the cellular structures in the aerogels. Particularly, a significant influence of angles between cell walls' orientated direction and electric field direction of incident EM waves on EMI shielding performance is displayed. This provides an intriguing and crucial concept for controlling EMI shielding performance based on the microstructural design strategy in EMI shielding applications. Taking complete advantage of the biomimetic cell walls and cellular structure, EMI SE of the MXene/CNF hybrid aerogels can reach as high as 74.6 or 35.5 dB at densities of merely 8.0 or 1.5 mg/cm3, respectively. The normalized surface-specific SE (defined as the SE divided by the material density and thickness) are up to 189400 dB·cm2/g, which significantly exceeding that of other EMI shielding materials reported so far. This work thus suggests a convenient, facile, low-cost, and scalable preparation approach for constructing high-performance porous macrostructures with potential applications in next-generation lightweight, flexible electronic devices and aerospace. Biography Zhihui, Zeng. Professor, Dr. Professor Zhihui Zeng currently works in the School of Materials Science and Engineering, Shandong University (SDU), Jinan, China. He received his Ph.D. degree in 2016 from the National Center for Nanoscience and Technology (NCNST), University of Chinese Academy of Sciences, Beijing, China. After obtaining the Ph.D. degree, he worked as a postdoctoral research fellow at Nanyang Technological University, Singapore (2016-2018) and in the Cellulose & Wood Materials Lab at Empa- Swiss Federal Laboratories for Materials Science and Technology, Switzerland (2018-2021). Till now, he has published ~40 papers including Adv. Mater., Adv. Funct. Mater. Adv. Sci., ACS Nano, Small, etc. with an h index of 20. His research interests include the design, fabrication, and application of multi-functional polymer-based nanocomposites, nanostructured assemblies, and cellular materials.

Developing high-performance and functional hydrogels that mimic biological materials in nature is promising yet remains highly challenging. Through a facile, scalable unidirectional freezing followed by a salting-out approach, a type of hydrogels composed of "trashed" MXene sediment (MS) and biomimetic pores is manufactured. By integrating the honeycomb-like ordered porous structure, highly conductive MS, and water, the electromagnetic interference (EMI) shielding effectiveness is up to 90 dB in the X band and can reach more than 40 dB in the ultrabroadband gigahertz band (8.2-40 GHz) for the highly flexible hydrogel, outperforming previously reported porous EMI shields. Moreover, thanks to the stable framework of the MS-based hydrogel, the influences of water on shielding performance are quantitatively identified. Furthermore, the extremely low content of silver nanowire is embedded into the biomimetic hydrogels, leading to the significantly improved multiple reflection-induced microwave loss and thus EMI shielding performance. Last, the MS-based hydrogels allow sensitive and reliable detection of human motions and smart coding. This work thus not only achieves the control of EMI shielding performance via the interior porous structure of hydrogels, but also demonstrates a waste-free, low-cost, and scalable strategy to prepare multifunctional, high-performance MS-based biomimetic hydrogels.

In this article, we report highly porous yet robust microhoneycomb-like nanofibrous aerogels (NFAs) with porous cell walls and hierarchical porous structures, and their potential as durable high-performance air filters. The NFAs are fabricated from cellulose nanofibers and kraft lignin via directional ice-templating and low-temperature annealing. We found that lignin could effectively boost cross-linking reactions during the annealing, greatly enhancing the mechanical robustness of the NFAs. It also effectively minimizes annealing-induced shrinkage of the NFAs, avoiding significant porosity and pore-size reduction. Our filtration test results reveal that these robust NFA filters exhibit excellent filtration performance for particles over a wide range of sizes, including 0.1 μm and most penetrating particles. In particular, a high filtration efficiency of 99.86% with a fairly low pressure drop (ΔP) of 59.5 Pa could be achieved for 0.1 μm particles at the face velocity of ∼5 cm s−1, for which the corresponding quality factor (QF) is significantly higher than that of reported aerogel air filters fabricated using predominantly natural materials. The outstanding QF achieved could be attributed to the preferably aligned pores and porous cell walls that help to ease the airflow and create longer and tortuous travelling paths for diffusive particles while within the pores the loose, tangled nanofibers with surface functional groups could facilitate particle deposition. Moreover, heavy loading filtration tests show good long-term filtration efficiency and anti-clogging features of the NFAs. Overall, this work provides a new strategy to prepare durable NFA air filters that are capable of mitigating the tradeoff between the filtration efficiency and ΔP, and alleviating the potential microplastic pollution caused by the disposal of petroleum-based plastic filters into environments. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Nanyang Technological University Xiu Yun Daphne Ma thanks Energy Research Institute @ NTU, Interdisciplinary Graduate School, and Nanyang Technological University for providing PhD scholarship in the course of this work. This work was also supported by Science and Engineering Research Council of the Agency for Science, Technology and Research (A*STAR) Singapore under Public Sector Research Funding (PSF) Grant No. 1521200077 and by the Republic of Singapore’s Ministry of Education MOE2016-T2-1- 063.

Ultralight and highly flexible biopolymer aerogels, composed of biomimetic cellular microstructures formed from cellulose nanofibers and silver nanowires, are assembled via a convenient and facile freeze-casting method. The lamellar, honeycomb-like, and random porous scaffolds are successfully achieved by adjusting freezing approaches to modulate the relationships between microstructures and macroscopic mechanical and electromagnetic interference (EMI) shielding performances. Combining the shielding transformation arising from in situ compression and the controlled content of building units, the optimized lamellar porous biopolymer aerogels can show a very high EMI shielding effectiveness (SE), which exceeds 70 or 40 dB in the X-band while the density is merely 6.2 or 1.7 mg/cm3, respectively. The corresponding normalized surface specific SE (defined as the SE divided by the material density and thickness) is up to 178235 dB·cm2/g, far surpassing that of the so-far reported shielding materials. Antibacterial properties and hydrophobicity are also demonstrated extending the versatility and application potential of the biopolymer hybrid aerogels.

Nanofibrillar foams and aerogels are traditionally either macroporous with low surface area and high mechanical strength, or mesoporous with high surface area and low mechanical strength. In this work, an anionic cellulose nanofibril (CNF)-based dual-porous aerogel with BET specific surface area up to 430 m2 g-1 was prepared via a modular process combining directional freeze-thawing (creating macro-pores, ca. 50-200 μm) and supercritical drying (creating meso-pores, ca. 2-50 nm). Furthermore, by optionally utilizing both physical and chemical cross-linking strategies, aerogels with a Young's modulus of up to 711 kPa and good stability in aqueous conditions were demonstrated. By altering cross-linking strategies, the properties of resulting aerogels, such as hydrophilicity, mechanical strength and stability in water, can be precisely controlled for different applications. As a result, cationic methylene blue (MB) and metal ions (Ag+) were chosen as model species to investigate the absorption properties of the physically cross-linked aerogels in water. The aerogels showed a maximum adsorption of MB up to 234 mg g-1 and of Ag+ up to 116 mg g-1 as a result of the high specific surface area of the aerogels and their strong electrostatic interaction with the model species. Importantly, the hierarchical dual porosity of the aerogels enabled fast adsorption kinetics combined with a considerable adsorption capacity overall. Finally, it was shown that the adsorbed Ag+ could be converted to metallic Ag, demonstrating the additional functionality of these dual porous hybrid aerogels for antibacterial or catalytic applications.

Nanofibrillated cellulose is efficiently employed as a green dispersant, cross-linker and structure-directing agent assisting in the preparation of large-area ambient pressure dried carbon nanotube (CNT) foams using a facile, energy-efficient, and scalable freezing–thawing–drying approach. The resultant CNT based foams show unidirectional microhoneycomb pore channels, high mechanical strength, good conductivity, controllable wide-ranging densities, and functional attributes of high-efficiency organic dye absorption and designed hydrophobicity. The significant pore microchannel orientation allows for a facile tuning of the electromagnetic interference (EMI) shielding performances of the CNT foams. This is demonstrated by efficiently controlling the angle of the pore orientation with respect to the electric field direction of the incident electromagnetic waves. Combining the adept controllability of the building blocks and the excellent EMI shielding effectiveness (SE) of more than 70 dB, resulting in a specific SE of up to 6111 dB cm2 g−1, our work shows the great potential of these air-dried nanostructured cellular monoliths in EMI shielding applications.