Macroporous Architecture Research Articles

3D Macroporous Oxidation‐Resistant Ti3C2Tx MXene Hybrid Hydrogels for Enhanced Supercapacitive Performances with Ultralong Cycle Life

AbstractAs a recently emerging group of 2D materials, MXene has attracted extensive attention in the energy storage field in recent years owing to their outstanding features. However, the notorious issues of inevitable oxidation stability and surface‐to‐surface self‐restacking for MXene significantly prevent its further wide‐ranging application. Herein, the 3D macroporous oxidation‐resistant Ti3C2Tx MXene/graphene/carbon nanotube (MRC) hybrid hydrogels are prepared by a simple gelation method assisted by l‐cysteine as crosslinker and l‐ascorbic acid (VC) as reductant. Benefitting from the effectively alleviated restacking, excellent electrical conductivity, and the 3D inter‐crosslinked macroporous architecture, as a supercapacitor electrode, the obtained MRC aerogel exhibits a superior specific capacitance of 349 F g−1, unparalleled rate capability (52.0% at 3000 mV s−1) and amazing cyclic stability (retention of 97.1% after 100 000 cycles). Moreover, the 3D MRC‐30 aerogel exhibits an impressive oxidation‐resistant performance with just a 9.3% increase in electrical resistance after storing in ambient condition for 60 days, effectively alleviating the oxidation problem of MXene. This work demonstrates a new method for construction of 3D oxidation‐resistant MXene hydrogel, shedding new light on the promising applications of MXene materials, especially in high humidity and oxygen environment.

Boosting Sodium Storage Performance of Hard Carbon Anodes by Pore Architecture Engineering.

Hard carbon (HC) displays great potential for high-performance sodium-ion batteries (SIBs) due to its cost-effective, simple fabrication and most likely to be commercialized. However, the complicated microstructures of HC lead to difficulties in deeply understanding the structure-performance correlation. Particularly, evaluation of influence of pore structure on Na storage performances is still causing disputes and rational strategies of designing pore architecture of HC are still necessary. In this work, the skillful and controllable phase-inversion method is applied to construct porous HC with abundantly interconnected and permeable tunnel-like pores, which can promote ionic diffusion and improve electrode-electrolyte interfacial affinity. Structure-performance investigation reveals that porous HC with cross-coupled macropore architecture can boost Na storage performances comprehensively. Compared to pristine HC with negligible pores, well-regulated porous HC anodes show an obvious enhancement on initial Coulombic efficiency (ICE) of 68.3% (only 51.5% for pristine HC), reversible capacity of 332.7 mAh g-1 at 0.05 A g-1, rate performance with 67.4% capacity retention at 2 A g-1 (46.5% for pristine HC), and cycling stability with 95% capacity maintained for 90 cycles (86.4% for pristine HC). Additionally, the ICE can be optimized up to 76% by using sodium carboxymethyl cellulose as a binder. This work provides an important view of optimizing Na storage performances of HC anodes by pore engineering, which can be broadened into other electrode materials.

Hierarchically ordered macroporous TiO2 architecture via self-assembled strategy for environmental remediation

Hierarchical orderd macroporous TiO2 architecture (HOMTA) was prepared with aid of ethylenediamine (EDA) and investigated the impact of amine molecules on the properties of TiO2 architecture. The different variation of amine molecules (EDA) leads to tunning the morphology under hydrothermal approach which is confirmed by FESEM and TEM analysis. The XRD and Raman studies confirms the crystal structure of anatase and brookite phase of TiO2. The surface of the architecture strongly depended on the concentration of EDA which plays a vital role in surface area which is revealed by Brunauer Emmett-Teller (BET) analysis. The obtained HOMTA was employed as photocatalyst and active photoanode in the dye sensitized solar cells (DSSC). The DSSC device exhibits excellent efficiency (η) of 5.27% for the EDA capped TiO2 (S5) which had high surface area (167.11 m2/g) for better dye loading, whereas the lower concentration of EDA capped TiO2 (S1, S2, S3 and S4) resulted the efficiency of 2.14, 3.90, 3.25 and 4.37%, respectively. The efficiency of photocatlysis degradation of the prepared samples (S1, S2, S3, S4 and S5) was 94.8, 90.47, 91.41, 91.32 and 93.75% under light source. The excellent photocatalysis property was achieved by S5 within 6 min due to high surface area which inducing more active site.

Anion-Doped Cobalt Selenide with Porous Architecture for High-Rate and Flexible Lithium-Sulfur Batteries.

Emerging catalytic host for sulfur is an effective approach to breaking the limits of lithium-sulfur batteries for practical applications. Herein, the hydrangea-shaped Co0.85 Se electrocatalyst with macroporous architecture is synthesized. Besides, to improve the electronic conductivity of Co0.85 Se, some defects (S-doped) are introduced into the structure of crystals. The S-doped Co0.85 Se exhibited an outstanding electrocatalytic effect on lithium polysulfides conversion and can induce and regulate uniform growth of insoluble Li2 S on its surface due to the synergistic adsorption by Se and S. As a result, the S/C cathode achieved a high initial capacity of 1340.6 mAh g-1 at 0.5 C and a stable cycling capacity of 666.6 mAh g-1 at 1 C after 500 cycles by 5wt% Co0.85 SeS additions. Moreover, high S loading cathodes are designed through in situ synthesis of Co0.85 SeS on flexible carbon cloth (Co0.85 SeS@CC). The porous and open framework of Co0.85 SeS@CC facilitated electrolyte infiltration and accommodated the volume change of sulfur during the charge/discharge process. Taking by these advantages, a high areal capacity of 9.663 mAh cm-2 is achieved at a high sulfur loading of 9.98mg cm-2 . Even at a high current density of 15mA cm-2 , a reversible capacity of 603.7 mAh g-1 is maintained at a sulfur loading of 6.52mg cm-2 . This proposed work provides a feasible approach to high-rate and flexible Li-S batteries.

Carbon aerogels with integrated engineered macroporous architectures for improved mass transport

Carbon aerogels (CAs) combine unique properties including ultra-high surface area, high electrical conductivity, corrosion resistance, and robust mechanical properties making them ideal materials for electrochemical applications. Traditional CA synthesis results in isotropic, random nanoporous networks that work well for applications relying on diffusional mass transport. However, many applications would benefit from integration of engineered macroporous network structures that enable directed pressure-gradient-driven mass transport. Here, we report on using 3D-printed sacrificial polymeric templates to generate templated CAs (t-CAs) with integrated engineered nonrandom macroporous network structures. Specifically, we used projection micro-stereo-lithography (PμSL) and two-photon polymerization direct laser writing (2PP-DLW) to fabricate millimeter-to-centimeter-sized 3D sacrificial polymeric templates with features ranging from tens of microns (PμSL) to 100s of nanometers (2PP-DLW). T-CAs were fabricated by infiltrating the templates with resorcinol-formaldehyde (RF) precursor solution, followed by carbonization at 1050 °C to simultaneously convert the RF gel to a CA and decompose the 3D-printed template, leaving an embedded templated macroporous network structure behind. X-ray computer tomography confirms integration of the macroporous architecture defined by the template. The templated macroporous architecture improves mass transport in t-CAs compared to traditional bulk CA as demonstrated by more uniform activation and their response in electrochemical cyclic voltammetry and galvanostatic charge-discharge tests.

Electrical Conductivity Adjustment for Interface Capacitive‐Like Storage in Sodium‐Ion Battery

AbstractSodium‐ion battery (SIB) is significant for grid‐scale energy storage. However, a large radius of Na ions raises the difficulties of ion intercalation, hindering the electrochemical performance during fast charge/discharge. Conventional strategies to promote rate performance focus on the optimization of ion diffusion. Improving interface capacitive‐like storage by tuning the electrical conductivity of electrodes is also expected to combine the features of the high energy density of batteries and the high power density of capacitors. Inspired by this concept, an oxide‐metal sandwich 3D‐ordered macroporous architecture (3DOM) stands out as a superior anode candidate for high‐rate SIBs. Taking Ni‐TiO2 sandwich 3DOM as a proof‐of‐concept, anatase TiO2 delivers a reversible capacity of 233.3 mAh g−1 in half‐cells and 210.1 mAh g−1 in full‐cells after 100 cycles at 50 mA g−1. At the high charge/discharge rate of 5000 mA g−1, 104.4 mAh g−1 in half‐cells and 68 mAh g−1 in full‐cells can also be obtained with satisfying stability. In‐depth analysis of electrochemical kinetics evidence that the dominated interface capacitive‐like storage enables ultrafast uptaking and releasing of Na‐ions. This understanding between electrical conductivity and rate performance of SIBs is expected to guild future design to realize effective energy storage.

Facile production of three-dimensional chitosan fiber embedded with zinc oxide as recoverable photocatalyst for organic dye degradation

Herein we report on a facile and green strategy for continuous production of chitosan-zinc oxide fibers and then compare their photodegradation performance against three organic dyes (i.e., methylene blue (MB), methyl orange (MO) and Rhodamine B, respectively) under different lights. Chitosan-zinc hydrogel fibers (CS/Zn) with different zinc loadings are obtained by direct mixing of chitosan and zinc acetate solutions using a double-syringe injection device. The as-prepared CS/Zn fibers are then immersed into glutaraldehyde (GA) and sodium hydroxide solutions, respectively, and dried at T = 50 °C. The resultant CS/ZnO/GA fibers of ca. 617 μm in diameter are characterized using X-ray diffraction (XRD), thermogravimetric analysis and field emission scanning electron microscope (FE-SEM). XRD and FE-SEM data confirm that the CS/ZnO/GA fibers consist of a large amount of hexagonal wurtzite ZnO nanorods up to 550 nm in length, and exhibit three-dimensional interconnected macroporous architecture. Photodegradation results clearly show that the CS/ZnO/GA fibers are effective for the removal of organic dyes upon UV irradiation and can be easily recovered and reused for at least 6 consecutive cycles. Unlike most reported CS/ZnO nanocomposites, the current CS/ZnO/GA fiber shows a higher adsorption of cationic MB rather than anionic MO, the mechanism of which is proposed.

3D macroporous architecture of self-assembled defect-engineered ultrathin g-C3N4 nanosheets for tetracycline degradation under LED light irradiation

Herein, the facile fabrication of a novel 3D macroporous structure of graphitic carbon nitride composed of self-assembled 2D nitrogen vacancy engineered nanosheets have been reported. The synthesis of the defect-engineered structure was achieved upon the addition of ethylene glycol during the solid-state synthesis process. The photocatalyst was characterized through a wide range of characterization techniques. The macroporous structure exhibited superior photocatalytic efficiency towards tetracycline antibiotic degradation under LED light illumination. The defect-engineered material (4EGCN) exhibited a 3.3-fold superior degradation rate coefficient of 0.010 min−1, compared to the degradation rate coefficient (0.003 min−1) of the bulk counterpart. This superior photocatalytic performance could be accredited to the extended visible light extraction efficiency, increased suppression efficacy of charge carriers, and porous structure. Moreover, the photocatalyst showed excellent stability even after five cycles of photocatalytic tetracycline degradation. Further, a probable degradation mechanism has been proposed according to the observations of the radical scavenging experiments.

Calendering-Compatible Macroporous Architecture for Silicon-Graphite Composite toward High-Energy Lithium-Ion Batteries.

Porous strategies based on nanoengineering successfully mitigate several problems related to volume expansion of alloying anodes. However, practical application of porous alloying anodes is challenging because of limitations such as calendering incompatibility, low mass loading, and excessive usage of nonactive materials, all of which cause a lower volumetric energy density in comparison with conventional graphite anodes. In particular, during calendering, porous structures in alloying-based composites easily collapse under high pressure, attenuating the porous characteristics. Herein, this work proposes a calendering-compatible macroporous architecture for a Si-graphite anode to maximize the volumetric energy density. The anode is composed of an elastic outermost carbon covering, a nonfilling porous structure, and a graphite core. Owing to the lubricative properties of the elastic carbon covering, the macroporous structure coated by the brittle Si nanolayer can withstand high pressure and maintain its porous architecture during electrode calendering. Scalable methods using mechanical agitation and chemical vapor deposition are adopted. The as-prepared composite exhibits excellent electrochemical stability of >3.6 mAh cm-2 , with mitigated electrode expansion. Furthermore, full-cell evaluation shows that the composite achieves higher energy density (932 Wh L-1 ) and higher specific energy (333 Wh kg-1 ) with stable cycling than has been reported in previous studies.

Electrospun carbon fibers as air cathodes for aprotic Li–O2 battery: Towards cathode design for enhanced capacity

This report investigates how the microstructures and chemical properties of carbon cathodes influence the discharge capacity of aprotic Li–O2 batteries. For that, electrospun carbon fibers (CFs), Multi-wall carbon nanotubes (MWCNTs), carbon Super P and gas diffusion layer (GDL) were fully discharged at various applied current densities (0.05–0.5 mA cm−2(geom)) and characterized by means of ex-situ techniques such as XRD and FEG−SEM. The major discharge product for every carbon electrode was identified as Li2O2 by both XRD and gas pressure analysis. The corresponding electrochemical results showed two different behaviors depending on the current density. At high current densities, all the carbon electrodes presented quite similar discharge capacities due to the most favored formation of Li2O2 conformal film on the carbon surface. In contrast, at lower current densities, the morphology of the discharge product changed and Li2O2 was preferably deposited as micrometer−sized toroïds particles on all the carbon cathodes (except for GDL). In this particular regime, the specific capacity normalized by the active carbon surface area of the electrospun CFs cathode was surprisingly promoted compared to the other carbon materials. Interestingly, it was found that unlike for the other cathode materials, Li2O2 homogenously occupies the void volume of the electrospun carbon structure without any pores clogging, which was attributed to its particular macroporous architecture presumably facilitating a continuous O2 diffusion through the electrode. The enhancement in discharge capacity might also be related to the presence of nitrogen active sites, as revealed by XPS analysis of the pristine carbon surface. All these features highlight that the carbon porosity and surface chemistry are key parameters to design efficient air cathodes for Li–O2 batteries performing at low current density.

Highly sensitive and selective acetone sensor based on three-dimensional ordered WO3/Au nanocomposite with enhanced performance

With the development of medical science, analyzing the concentration of the volatile organic compounds (VOCs) in expiration has been considered as a rapid, convenient and noninvasive method for medical diagnosis. The detection of diabetes with acetone as a marker has received extensive attention, but the development of a highly sensitive acetone sensor remains various challenges to improve the sensing performance with nanostructure-controllable novel materials. In this work, an acetone sensor based on three-dimensional inverse opal (3DIO) tungsten oxide (WO3) composite modified with Au (WO3/Au) was obtained through a simple sacrificial template synthesis, which provided more active sites with macropore architecture. Moreover, with modification of Au nanoparticles (NPs), it is obvious that gas sensing property with “spillover effects” and catalytic action was obtained. The 3DIO WO3/Au gas sensor exhibited good selectivity to acetone, and showed great test performance from 100 ppb to 100 ppm. A corresponding actual detection limit of 100 ppb at 410 °C was realized, which could allow real-time and reliable diagnosis of diabetic by acetone monitoring. Furthermore, it also showed good stability and faster response and recovery times compared with pure WO3 sensors. The 3DIO WO3/Au gas sensor shows great potential in practical application of a noninvasive and more accurate monitoring and detection of diabetes.

(Invited) Advanced Inorganic and Polymer Nanocomposite Materials for Fuel Cell Applications

The widespread adoption of clean energy converters such as proton exchange membrane fuel cells (PEMFC) is mainly hindered by the degradation of their component materials over time. To overcome this issue, our approach is based on the preparation of nanocomposite materials based on inorganic and polymer nanofibers with specific structures and improved properties. The size and morphology of the fibres and the macroporous architecture of the corresponding webs may bring improved mass transport and mechanical properties, with beneficial effects on the performance and lifetime of the resulting membrane-electrode assemblies (MEAs).Among the methods for generating nanostructures, electrospinning is a top-down approach with the advantages of simplicity, high yield, low cost, high degree of reproducibility and ease to scale-up from an industrial perspective. The versatility of the technique allowed its application to all stages of the preparation of PEMWE materials, from electrolyte membranes to electrodes.Polymer and inorganic fibre networks obtained by electrospinning are used to prepare reinforced membranes [1, 2]. This reinforcement, further intensified by ionic interactions between the fibres and the ionomer, extends the MEA lifetime and enables the fabrication of thinner membranes improving the PEMFC performance by lowering the electrical resistance.Hierarchical structuring of electrodes was achieved using nanofibre catalyst supports and the deposition of catalyst nanoparticles, thin films or active sites on them. With this strategy we can prepare corrosion resistant supports including metal oxides doped with a range of aliovalent ions, with extended durability and high electrical conductivity [3]. A range of deposition techniques including Ni and Cu galvanostatic displacement, high overpotential pulsed Pt electrodeposition [4-6] and atomic layer deposition are investigated to prepare highly active ultra-low loaded electrodes.This association of deposition techniques opens up a broad range of opportunities for tuning materials composition and architecture to develop and upscale a new generation of PEMFC cores.

Excellent Methanol to Olefin Performance of SAPO-34 Crystal Deriving from the Mixed Micropore, Mesopore, and Macropore Architecture

Hierarchical aluminosilicophosphate SAPO-34 crystals with designed micropore, mesopore, and macropore architecture are successfully prepared via a simple in situ base etching; the volume ratio of m...

Macroporous 3D MXene architecture for solar-driven interfacial water evaporation

Interfacial water evaporation through solar heating with photothermal materials is a promising strategy for seawater desalination and wastewater purification. Tightly packed 2D membranes with high reflection losses and limited vapor escape channels result in a low evaporation rate. In this work, 3D MXene architecture was fabricated by dropping the delaminated Ti3C2 ([Formula: see text]-Ti3C2) nanosheets onto the carbonized melamine foam (CMF) framework. Owing to the macroporous 3D architecture, more effective broadband solar absorption and vapor escaping were achieved. As a result, the 3D CMF@[Formula: see text]-Ti3C2-based evaporator delivers a water evaporation rate of 1.60[Formula: see text]kg/m2[Formula: see text][Formula: see text][Formula: see text]h with a solar-to-vapor conversion efficiency of up to 84.6%.

Small Caliber Compliant Vascular Grafts Based on Elastin-Like Recombinamers for in situ Tissue Engineering.

Vascular disease is a leading cause of death worldwide, but surgical options are restricted by the limited availability of autologous vessels, and the suboptimal performance of prosthetic vascular grafts. This is especially evident for coronary artery by-pass grafts, whose small caliber is associated with a high occlusion propensity. Despite the potential of tissue-engineered grafts, compliance mismatch, dilatation, thrombus formation, and the lack of functional elastin are still major limitations leading to graft failure. This calls for advanced materials and fabrication schemes to achieve improved control on the grafts' properties and performance. Here, bioinspired materials and technical textile components are combined to create biohybrid cell-free implants for endogenous tissue regeneration. Clickable elastin-like recombinamers are processed to form an open macroporous 3D architecture to favor cell ingrowth, while being endowed with the non-thrombogenicity and the elastic behavior of the native elastin. The textile components (i.e., warp-knitted and electrospun meshes) are designed to confer suture retention, long-term structural stability, burst strength, and compliance. Notably, by controlling the electrospun layer's thickness, the compliance can be modulated over a wide range of values encompassing those of native vessels. The grafts support cell ingrowth, extracellular matrix deposition and endothelium development in vitro. Overall, the fabrication strategy results in promising off-the-shelf hemocompatible vascular implants for in situ tissue engineering by addressing the known limitations of bioartificial vessel substitutes.

Tailoring Aerogels and Related 3D Macroporous Monoliths for Interfacial Solar Vapor Generation

AbstractInterfacial solar vapor generation is emerging as a promising water treatment technology with high solar energy efficiency and minimized carbon footprint. Among various kinds of materials development, aerogels, with inherent high porosity, lightweight, enhanced absorption, and minimized thermal conductivity, are attracting significant attention for achieving high‐performance solar vapor generation. Herein, recent progress in tailoring aerogels (such as graphene [oxide], carbon nanotubes, and polymer aerogels) and related 3D macroporous architectures for interfacial solar vapor generation is presented. Furthermore, the challenges and opportunities associated with employing aerogels in solar vapor generation are also discussed.

Linking 3-D soil macropores and root architecture to near saturated hydraulic conductivity of typical meadow soil types in the Qinghai Lake Watershed, northeastern Qinghai–Tibet Plateau

The importance of soil macropores has been wildly recognized, which permit the rapid flow of water through soils. However, few studies have focused on the soil macropores of different alpine meadow soil in cold environments in the Qinghai-Tibet Plateau. This study aims to use computed tomography to quantify the soil macropore and root architecture of Meadow swamp soil, Sub-alpine shrub meadow soil, Sub-alpine grassland meadow soil and Sub-alpine meadow soil in the Qinghai Lake Watershed of the northeastern Qinghai-Tibet Plateau. A total of twelve soil cores (0–50 cm deep) were collected at four typical soil types under alpine meadow, with three replicates. At each site, the collected cores were scanned using the X-ray 3D microscope (Nano Voxel-2000, Sanying Precision Instruments Co., Ltd.). The soil macropores and root architecture of the soil cores were explored using the X-ray computed tomography method. The results indicated that the Meadow swamp soil and Sub-alpine shrub meadow soil had higher macropores than Sub-alpine grassland meadow soil and Sub-alpine meadow soil. Sub-alpine grassland meadow soil and Sub-alpine meadow soil had macropores that were mainly concentrated in the 0–100-mm soil depth. Moreover, macropore networks of Meadow swamp soil and Sub-alpine shrub meadow soil were more convoluted and continuous than those of Sub-alpine grassland meadow soil and Sub-alpine meadow soil. Root density was greater in the Meadow swamp soil and Sub-alpine shrub meadow soil than those in the Sub-alpine meadow soil and Sub-alpine grassland meadow soil. The soil macropore architecture with a high continuity could facilitate greater water flow to deeper soil layers in the Meadow swamp soil and Sub-alpine shrub meadow soil than in the Sub-alpine grassland meadow soil and Sub-alpine meadow soil. Root density, root node density, length density and surface area density and branch density were important parameters influencing soil macropore. Soil macropore length density was significantly and positively correlated to soil near saturated hydraulic conductivity K (10). Soil water status and alpine shrub root induce greater macroporosity of Meadow swamp soil and Sub-alpine shrub meadow soil than Sub-alpine grassland meadow soil and Sub-alpine meadow soil, and thus present a greater likelihood of larger macropores.

Injectable, Hyaluronic Acid-Based Scaffolds with Macroporous Architecture for Gene Delivery.

Biomaterials can provide localized reservoirs for controlled release of therapeutic biomolecules and drugs for applications in tissue engineering and regenerative medicine. As carriers of gene-based therapies, biomaterial scaffolds can improve efficiency and delivery-site localization of transgene expression. Controlled delivery of gene therapy vectors from scaffolds requires cell-scale macropores to facilitate rapid host cell infiltration. Recently, advanced methods have been developed to form injectable scaffolds containing cell-scale macropores. However, relative efficacy of in vivo gene delivery from scaffolds formulated using these general approaches has not been previously investigated. Using two of these methods, we fabricated scaffolds based on hyaluronic acid (HA) and compared how their unique, macroporous architectures affected their respective abilities to deliver transgenes via lentiviral vectors in vivo. Three types of scaffolds-nanoporous HA hydrogels (NP-HA), annealed HA microparticles (HA-MP) and nanoporous HA hydrogels containing protease-degradable poly(ethylene glycol) (PEG) microparticles as sacrificial porogens (PEG-MP)-were loaded with lentiviral particles encoding reporter transgenes and injected into mouse mammary fat. Scaffolds were evaluated for their ability to induce rapid infiltration of host cells and subsequent transgene expression. Cell densities in scaffolds, distances into which cells penetrated scaffolds, and transgene expression levels significantly increased with delivery from HA-MP, compared to NP-HA and PEG-MP, scaffolds. Nearly 8-fold greater cell densities and up to 16-fold greater transgene expression levels were found in HA-MP, over NP-HA, scaffolds. Cell profiling revealed that within HA-MP scaffolds, macrophages (F4/80+), fibroblasts (ERTR7+) and endothelial cells (CD31+) were each present and expressed delivered transgene. Results demonstrate that injectable scaffolds containing cell-scale macropores in an open, interconnected architecture support rapid host cell infiltration to improve efficiency of biomaterial-mediated gene delivery.

Self-assembly of ultralight and compressible inorganic sponges with hierarchical porosity by electrospinning

The construction of three dimensional macroporous architectures holds exciting implications for applications such as catalysis, sensing, tissue engineering and thermal insulation. Here, we report a general self-assembly process for inorganic sponges with hierarchical porosity of intrafibre micro-/meso-/macropores and interfibre macropores. The as-fabricated SiO2-TiO2 sponge possesses a high porosity of >99.86%, ultralow bulk density of 2.9 mg cm−3 and enhanced compressibility (recovery from 50% compression). The self-assembly mechanism of the SiO2-TiO2 sponge has been investigated in detail. The results confirmed that the hydrolysis and polycondensation of mixed inorganic alkoxides could affect the solidification process and the charge transpote during electrospinning, and plays an essential role on the hierarchical porosity and the self-assembly of the sponge macro-structure. The concerted effects of the solidification and electrostatic repulsion between fibres are responsible for the self-assembly process of the electrospun PVP-SiO2-TiO2 sponge. When used as a thermal insulation material, the SiO2-TiO2 sponge shows good fireproof performances. The current contribution may guide more construction of functional inorganic macroporous architectures for advance applications in future.

Three-dimensional cryogels for biomedical applications.

Cryogels are a subset of hydrogels synthesized under sub-zero temperatures: initially solvents undergo active freezing, which causes crystal formation, which is then followed by active melting to create interconnected supermacropores. Cryogels possess several attributes suited for their use as bioscaffolds, including physical resilience, bio-adaptability, and a macroporous architecture. Furthermore, their structure facilitates cellular migration, tissue-ingrowth, and diffusion of solutes, including nano- and micro-particle trafficking, into its supermacropores. Currently, subsets of cryogels made from both natural biopolymers such as gelatin, collagen, laminin, chitosan, silk fibroin, and agarose and/or synthetic biopolymers such as hydroxyethyl methacrylate, poly-vinyl alcohol, and poly(ethylene glycol) have been employed as 3D bioscaffolds. These cryogels have been used for different applications such as cartilage, bone, muscle, nerve, cardiovascular, and lung regeneration. Cryogels have also been used in wound healing, stem cell therapy, and diabetes cellular therapy. In this review, we summarize the synthesis protocol and properties of cryogels, evaluation techniques as well as current in vitro and in vivo cryogel applications. A discussion of the potential benefit of cryogels for future research and their application are also presented.