Macroporous Network Research Articles

Separation of Soil Macropore Types in Three‐Dimensional X‐Ray Computed Tomography Images Based on Pore Geometry Characteristics

Core Ideas For preferential flow modeling, different macropore types must be considered. A method was developed for separating biopores and cracks in 3D images from XRCT. The method enabled a more objective determination of structuring element sizes. The voxel‐based approach was found useful for quantification of macropore types. In structured soils, earthworm burrows, root channels, shrinkage cracks, and interaggregate spaces form complex macropore networks. Depending on the type and morphological properties, each macropore surface type is coated with specific organo‐mineral compounds, differently affecting sorption and mass exchange during preferential flow and turnover processes. For a quantitative, macropore type–specific analysis using X‐ray computed tomography (XRCT) with subsequent three‐dimensional (3D) image analysis, a discrimination of biopores from cracks and interaggregate spaces is necessary. We developed a method that allows separating biopores from other larger macropores in 3D images from XRCT of intact soil cores. An image‐processing workflow using the MAVI (Modular Algorithms for Volume Images) software framework ToolIP (Tool for Image Processing) was created to handle XRCT 3D images. Masking steps enabled to retain the surface roughness in the resulting two images of separated biopores and cracks. As a key point, the sizes of the structuring elements used in the spherical opening and dilation were objectively determined. For this purpose, maximum differences in the pore shapes between the 3D images of cylindrical biopores vs. more flat cracks and unregularly interaggregate spaces were focused. At the given resolution of 231‐μm voxel edge length, an optimum size of 2.5 voxels was found for both processing steps. The voxel‐based approach is applicable to XRCT 3D images of different spatial resolution and appears useful for the quantification of physicochemical surface properties of different macropore types for soil volumes, enabling a more precise description of preferential flow and transport.

High Performance Supercapacitor Applications and DC Electrical Conductivity Retention on Surfactant Immobilized Macroporous Ternary Polypyrrole/Graphitic-C3N4@Graphene Nanocomposite

Electrically conductive conducting polymer nanocomposites with carbonaceous materials have attraction the attention worldwide in resolving the energy crisis for economic reasons, ease of fabrication and easily controllable variable redox chemical states. In this work, highly conducting polypyrrole/g-C3N4@graphene (PPy/g-C3N4@GN) has been fabricated by polymerizing pyrrole with g-C3N4 along with surfactant para toluene sulfonic acid (pTSA) and later incorporating it with GN by hydrothermal methodology to form a macroporous network of pTSA doped PPy/g-C3N4@GN. Thus prepared PPy/g-C3N4@GN composite was characterized for the morphological characterizations by scanning electron microscopy, transmission electron microscopy while the structural characterizations were done by X-ray powder diffraction and X-ray photoelectron spectroscopy. The morphological analysis showed that the PPy and g-C3N4 were well distributed inside the GN sheets thereby forming structures of high porosity. The PPy and g-C3N4 were sandwiched between the sheets of GN and such morphology is expected to promote the electron transfer. The PPy/g-C3N4@GN composite showed high conductivity of 8.8 S/cm and exceptionally high thermal stability in aging thermal conductivity experiments. The high conductivity and stability is attributed to the contribution of following factors i.e. the high stability of g-C3N4, high conductivity of GN and PPy. Three electrode assembly was used to study the electrochemical supercapacitive characteristics; cyclic voltammetric curves and galvanostatic charge discharge measurements of PPy/g-C3N4@GN. The obtained nanocomposite delivered high capacitance of 260.4 F g−1 at a current load of 1 A g−1 as well as excellent 80% cyclic stability after the continuous 2000 charge discharge cycles. The enhanced performance is due the interaction between all the constituents in the present nanocomposites and improved electrical conductivity.

Elaboration of spherical particles of PMMA/ZnO through macroporous polymer networks

In this study, it is explained how spherical particles of poly(methyl methacrylate) (PMMA)/ZnO were synthesised in the presence of a polymer matrix of galactopyranose for their control growth. The objective of this research is to show the development of particles using the sol–gel method and the participation of a polysaccharide network. This method can increase the formation of stable spherical particles due to the hydrogen bonds junctions present in the walls of the polysaccharide network. The results of the formed tablets immersed in simulated body fluid indicate that there is no evidence of corrosion in the presence of PMMA/ZnO nanoparticles. The maximum roughness average (R max) and roughness value (R a) were 0.41 and 1.27 nm, respectively. The absorbance values showed significant changes when 10% polysaccharide concentration was used both in the presence and absence of the PMMA/ZnO nanoparticles. The particles were characterised by scanning electron microscopy, atomic force microscopy, powder X-ray diffraction (PXRD), X-ray elemental mapping, ultraviolet–visible spectrophotometry, and energy dispersive X-ray spectroscopy. The PXRD analysis shows the crystalline and amorphous phases of the composite at 400°C. The size range of the synthesised particles was between 30 and 100 µm.

Identifying the dominant controls on macropore flow velocity in soils: A meta-analysis

Macropore flow is a ubiquitous hydrologic process that has not been well explained using traditional hydrologic theories. In particular, macropore flow velocity (MFV) is poorly understood with respect to its typical ranges and controlling factors. Here we conducted a meta-analysis based on an MFV dataset compiled from 243 measurements documented in 76 journal articles. The dataset includes MFV values measured using different approaches across the soil-core, field-profile, and trench scales. Our analyses show that MFV has a geometric mean of 1.08×10-3ms-1, which is about 2~3 orders of magnitude larger than the corresponding values of saturated hydraulic conductivity in the soil matrix. Using machine learning methods including classification and regression tree and random forests algorithms, we identified observation scale, travel distance, rainfall intensity and macropore diameter as the most important factors that control MFV. MFV is much larger at the trench scale than at the other two scales mainly due to abundant large macropores. Correlation analysis and multivariate regression revealed that (1) MFV and rainfall intensity have significant positive correlation, which indicates that MFV is a dynamic variable; and (2) MFV and macropore diameter also have strong positive correlation at the trench scale, which indicates macropore size as a key controlling factor. Using macropore diameter and rainfall intensity as explanatory factors, MFV can be well predicted (R2 = 0.76) by a multivariate regression equation at trench-scale, implying that rainfall intensity can be considered a proxy for the filling degree of macropores. Furthermore, both the Poiseuille and Manning equations were found to overestimate the MFV values, suggesting a parameter representing the connectivity of the macropore network is needed for providing reasonable estimates of MFV using physically-based equations.

Design of lightweight metakaolin based geopolymer foamed with hydrogen peroxide

Monolithic metakaolin based geopolymer foams were synthetized by direct foaming using hydrogen peroxide (H2O2) as a blowing agent and surfactants to stabilize the resulting gas bubbles. The influence of the H2O2 content and the nature of the surfactant (cationic vs air entraining) have been investigated in the liquid and the solid state. The reaction rate constants for the oxygen produced by the catalytic decomposition of hydrogen peroxide (k = 5.5 × 10−4 and 2.1 × 10−4 s−1 for the air entraining and cationic based geopolymer foams, respectively) are reported for the first time, as calculated from volume expansion data in the liquid state. These constants were found to be independent of the initial H2O2 content. In the solid state, although the physical, mechanical, and microstructural properties of the resulting foams are known to be influenced by the amount of H2O2 in the geopolymer paste, the chemical composition of the surfactant had a startling effect on the morphology and topology of the macroporous network. Indeed, while faceted closed pores form in the cationic based geopolymer, a 3D network of connected pores forms in the air entraining one. As expected therefore, the cationic samples were found to have a much higher compressive strength than the air entrained ones (0.57–5.9 MPa compared with 0.26–4.3 MPa, respectively) for equivalent apparent densities (varying from 0.23 to 1.1 g cm−3).

From sol\u2013gel prepared porous silica to monolithic porous Mg2Si/MgO composite materials

Mg2Si is apart from its conductivity properties expected to be a promising candidate for thermoelectric applications due to its low toxicity, low costs, and the high abundance of its precursor chemicals. Through the addition of a homogeneous distribution of nanoparticles (e.g. MgO) and by reducing the size of Mg2Si to the nanometer regime, it is possible to decrease the thermal conductivity by increasing phonon-interface scattering and, as a result, improve the thermoelectric properties. However, classical approaches do not allow for the synthesis of nanocomposites from Mg2Si and MgO. In this work, a straightforward route is presented towards homogeneously mixed Mg2Si/MgO via a two-step magnesiothermic reduction process starting from sol–gel derived hierarchically organized porous silica. Monolithic materials composed of Mg2Si and MgO in variable molar ratios are built up from a macroporous network of Mg2Si with homogeneously distributed MgO particles exhibiting a crystallite size in the range of 24–37 nm.

Three-dimensional porous carbon frameworks derived from mangosteen peel waste as promising materials for CO2 capture and supercapacitors

Abstract Business costs, environmental and energy concerns have increased interest in biomass materials for the production of porous carbon materials, especially as solid-state adsorbents for CO2 capture or as electrode materials for supercapacitors. We put forward an efficient and scalable approach to convert mangosteen peel (MP) waste into three-dimensional microporous carbon frameworks (3D-MP-CFW) for effective CO2 capture and supercapacitors. The MP waste is first subjected to a controllable hydrothermal treatment in alkaline solution and then a carbonization process. The resultant optimal carbon sample possesses a high surface area up to 1270 m2 g−1 and abundant micropores with fine micropore sizes below 1 nm. The typical sample has a well-tailored open 3D macroporous interconnected network structure, exhibiting an outstanding CO2 capture recyclability and high CO2 capture capacities of 6.93 and 4.77 mmol g−1 at 0 °C and 25 °C (1 bar), respectively. Simultaneously, benefiting from its high surface area and 3D interconnected porous structure, this optimal sample also exhibits a good supercapacitance performance with the specific capacitance of 240 F g−1 (in 6 M KOH, at 1 A g−1) in a three-electrode system. Our simple preparation method presents an efficient way to make promising carbon materials for high-performance CO2 capture and supercapacitors.

Hierarchical porous carbon sheets derived from biomass containing an activation agent and in-built template for lithium ion batteries

We report a new strategy for synthesizing two-dimensional (2D) hierarchically porous carbon (HPC) based on soft pitch as the carbon source and oyster shell as both the template and activation agent precursor. The confined space of the sheet-like CaCO3 in oyster shell allows the soft pitch to diffuse and coat the in-built template, and the resultant 2D carbon derived from pyrolysis of the pitch inherited the sheet-like morphology of the template. Furthermore, CaCO3 can be easily converted into CaO, which acts as the self-activation agent to produce interconnected micro-, meso-, and macroporous carbon networks. The specific surface area of the resultant HPC was tuned from 612 to 1258 m2 g−1 by varying the pyrolysis time at 900 °C, and the resulting micro/meso-pore sizes were in the range of 0.7–9.5 nm. When used as the electrode of a lithium ion battery (LIB), the HPC exhibited a high reversible capacity of 1251 mAh g−1 at 0.1 A g−1 with excellent cycle stability. These results indicate that the 2D layered structure might effectively shorten the solid-state diffusion distance for Li ions in a LIB during the charging and discharging process. The interconnected hierarchical porous structure also improved the capacitance.

Boosting sodium storage properties of titanium dioxide by a multiscale design based on MOF-derived strategy

Cost-effective sodium-ion batteries (SIBs) are the most promising candidate for grid-scale energy storage. However, the lack of suitable high-performance anode materials has hindered their large-scale applications. In this study, we report a multiscale design to optimize a TiO2-based anode from atomic, microstructural, and macrostructural levels. A key point in our design is the use of Co-doped amine-functionalized Ti-MOFs as multi-functional precursors, which not only achieves Co, N double-doping, and encapsulation of ultrafine TiO2 nanoparticles in mesoporous C frameworks, but also endows the precursors with positive surface charges, driving them to combine with graphene nanosheets into a 3D macroporous network architecture by self-assembly. The well-designed anode delivered high reversible capacities of 174 mA h g−1 at 6 C for over 5000 cycles, 121 mA h g−1 at 15 C for over 10,000 cycles, and 100 mA h g−1 at 30 C for over 3000 cycles, demonstrating the most efficient TiO2-based anode ever reported for SIBs. The unprecedented sodium storage performance is attributed to the multiscale integration yielding a high content of oxygen vacancies, 3D continuous conductive networks, and open diffusion channels, promoting both electron conduction and Na+ diffusion not only inside and around the TiO2 nanoparticles but also through overall electrode. The unique multiscale design based on MOF-derived strategy holds great potential in generalizable synthesis of versatile electrode materials for advanced battery systems.

Structure and hydraulic properties in soils under long-term irrigation with treated wastewater

Secondary treated wastewater, a commonly used water resource in agriculture in (semi-)arid areas, often contains salts, sodium, and organic matter which may affect soil structure and hydraulic properties. The main objective of this study was to jointly analyse the effects of long-term irrigation with treated wastewater on physicochemical soil characteristics, soil structure, and soil water dynamics in undisturbed soils. X-ray microtomography was used to determine changes in macro-porosity (> 19 μm), pore size distribution, and pore connectivity of a sandy clay loam and a loamy sand. Differences in the pore network among soils irrigated with treated wastewater, fresh water that replaced treated wastewater, and non-irrigated control plots could be explained by changes in textural composition, soil physicochemical parameters, and hydraulic properties. In this study we showed that irrigation led to the development of a connected macro-pore network, independent of the studied water quality. The leaching of silt and clay particles in the sandy soil due to treated wastewater irrigation resulted in an increase of pores < 130 μm. While this change in texture reduced water retention, the unsaturated hydraulic conductivity was diminished by physicochemical alteration, i.e. induced water repellency and clay mineral swelling. Overall, the fine textured sandy clay loam was much more resistant to soil alteration by treated wastewater irrigation than the loamy sand.

Solution growth of 3D MnO2 mesh comprising 1D nanofibres as a novel sensor for selective and sensitive detection of biomolecules

This work is the first report describing the solution grown 3D manganese oxide nanofibrous (MnO2 NFs) mesh and its potential for the simultaneous detection of biomolecules such as ascorbic acid and uric acid. The mesh is synthesized by a facile, one-pot, and cost-effective hydrothermal approach without using any template or structure directing compound. The morphology consists of randomly placed nanofibres possessing a diameter in the range of 10–25 nm, and length of several micron; constituting a highly porous and flexible material. The electrochemical potential was examined by recording cyclic voltammetry signals towards ascorbic acid and uric acid. The special mesh morphology offers a large surface area to promote enhanced electrochemical activity, and also provided a macroporous network that supported efficient mass transport. Additionally, the strong electronic cloud and roughness of MnO2 NFs mesh facilitated the fast oxidation of species at very low potential. The lower detection limit was found to be 1.33 µM (S/N = 3) and 1.03 µM (S/N = 3) for ascorbic acid and uric acid, respectively. The MnO2 NFs mesh modified electrodes can robustly differentiate both of them by giving well separate signals (Δ = 500 mV) indicating capability of the material towards selective detection. The sensor has been successfully applied to human blood and urine samples and the recoveries were found statistically significant. These results demonstrate the practical feasibility of 3D mesh to develop sensors for the accurate diagnosis of clinically important molecules.

Impacts of forest conversion and agriculture practices on water pathways in Southern Brazil

AbstractLand‐use/cover change (LUCC), and more specifically deforestation and multidecadal agriculture, is one of the various controlling factors of water fluxes at the hillslope or catchment scale. We investigated the impact of LUCC on water pathways and stream stormflow generation processes in a subtropical region in southern Brazil. We monitored, sampled and analysed stream water, pore water, subsurface water, and rainwater for dissolved silicon concentration (DSi) and 18O/16O (δ18O) signature to identify contributing sources to the streamflow under forest and under agriculture. Both forested and agricultural catchments were highly responsive to rainfall events in terms of discharge and shallow groundwater level. DSi versus δ18O scatter plots indicated that for both land‐use types, two run‐off components contributed to the stream discharge. The presence of a dense macropore network, combined with the presence of a compact and impeding B‐horizon, led to rapid subsurface flow in the forested catchment. In the agricultural catchment, the rapid response to rainfall was mostly due to surface run‐off. A 2‐component isotopic hydrograph separation indicated a larger contribution of rainfall water to run‐off during rainfall event in the agricultural catchments. We attributed this higher contribution to a decrease in topsoil hydraulic conductivity associated with agricultural practices. The chemical signature of the old water component in the forested catchment was very similar to that of the shallow groundwater and the pore soil water: It is therefore likely that the shallow groundwater was the main source of old water. This is not the case in the agricultural catchments where the old water component had a much higher DSi concentration than the shallow groundwater and the soil pore water. As the agricultural catchments were larger, this may to some extent simply be a scale effect. However, the higher water yields under agriculture and the high DSi concentration observed in the old water under agriculture suggest a significant contribution of deep groundwater to catchment run‐off under agriculture, suggesting that LUCC may have significant effects on weathering rates and patterns.

In situ characterization of preferential flow by combining plot- and point-scale infiltration experiments on a hillslope

This study focuses on the identification of the lateral preferential flow at the hillslope scale and the estimation of the saturated hydraulic conductivity for the fast-flow region, Ks,f, based on infiltration experiments carried out at different spatial scales (point- and plot-scales), and at different soil depths. The discrepancies between the considered scales were mainly attributed to macropore flow and the difficulty in adequately embodying the macropore network on small sampled soil volumes. Conversely, at the plot-scale, the sampled volume was sufficient to activate the macropore network. This information helped establish the usability of a given technique to determine the parameters describing the hydraulic properties of the soil in the matrix and fast-flow regions. While Ks data obtained from the Beerkan method with the Beerkan Estimation of soil Transfer (BEST) parameter algorithm (point-scale) were used to describe the matrix (Ks,m), the saturated hydraulic conductivity for the fast-flow region was estimated using the soil block method (plot-scale). Estimated Ks,f values were one to three orders of magnitude higher than Ks,m. The overall decrease of Ks,f with the soil depth supported the hypothesis that the macropore density decreased as a function of depth, yielding higher macropore flow variability. The soil block method, in association with the Beerkan infiltration runs, allowed the estimation of the saturated hydraulic conductivity for the fast-flow region based on a relatively simple field procedure.

Microarchitecture of poly(lactic acid) membranes with an interconnected network of macropores and micropores influences cell behavior

Tissue engineering scaffolds require a three-dimensional architecture with controlled pore size and structure to host tissue formation. Here we used the non-solvent induced phase separation (NIPS) process to prepare porous asymmetric membranes made of poly(lactic acid) (PLA) using dimethylformamide (DMF) as solvent and water as non-solvent. The addition of a polymer additive to the PLA solution has made it possible to increase and control the size of open macropores at the membrane bottom surface and to generate a dual pore architecture consisting of an interconnected network of macropores and micropores. Based on the study of the compatibility of PLA with the polymer additive we propose that the dual pore architecture is generated through a two phase separations process. Membrane surface could be functionalized with hyaluronan (HA) and, whatever the cell type considered, HA-functionalization enhanced cell proliferation. Interestingly, a strong effect of macropore size and surface functionalization by HA on cell colonization and cell proliferation within membranes and membrane morphology on cell organization was demonstrated. Cancer cell lines were able to adopt an in vivo tumor-like behavior, endothelial cells reconstituted a vascular-like structure and mesenchymal stem cells adopted a specific organization which can open perspectives for their use and conservation. These results show that our membranes with controllable dual pore architecture offer great potentialities in tissue and tumor engineering.

Tensile strength during drying of remoulded and compacted clay: The role of fabric and water retention

Abstract The paper presents an experimental investigation on the tensile strength of an unsaturated clay, both in remoulded and compacted states. To complete the experimental study, a new apparatus was designed with the purpose of determining direct tensile stress under controlled-displacement or controlled-force. The design exploits a direct shear test box, which was adapted to the scope of this investigation. Three different hydro-mechanical paths were followed before the tensile strength was determined: a) drying paths on remoulded samples; b) drying paths after compaction at different initial water contents; and c) dynamic compaction at different water contents, hence at different suctions and degrees of saturation. A microstructural investigation was also performed to better understand the experimental results and obtain the most relevant physical parameters. The preparation methods induced different initial fabrics, which dominated the water retention properties, as well as the tensile strength behaviour. A recent model for water retention, including the effects of multimodal fabric, was calibrated on available data and used to predict the suction of the samples along the drying paths, where direct information was not available. A simple model for tensile strength was proposed for its evolution, which included the role of multimodal fabric and their different water storage capabilities, the evolution of dry density and the initial water content (at the beginning of the tensile test path). For the compacted sample, typically showing a multimodal pore size distribution, the tensile strength was found to be a function of the state variables describing the macropore network. Dry density increases on drying appeared in all the cases to dominate the tensile response, Water exchange and suction increase were well correlated to the tensile response evolution.

Effects of tillage and liming on macropore networks derived from X‐ray tomography images of a silty clay soil

AbstractSoil structure influences water infiltration, aeration and root growth and, thereby, also the conditions for sustainable crop production. Our objective was to quantify the effects of different soil management methods and land uses on the topsoil structure of a silty clay soil. We sampled 32 intact soil columns (18 cm high, 12.7 cm diameter) from an experimental silty clay field with four treatments: conventional tillage (CT), conventional tillage followed by liming (CTL), reduced tillage (RT) and unfertilized fallow (UF). The columns were analysed using 3‐D X‐ray tomography. The samples were taken in autumn after harvest, 7 yr after quick lime was applied to the CTL plots. Despite a relatively large number of replicates per treatment (8, 8, 8 and 6 (two UF samples were excluded), respectively), there were no significant differences between any of the investigated macropore network properties related to tilled treatments. The UF treatment, in contrast, exhibited more vertically oriented macropores, which were also better connected compared to the other treatments. This confirms previous findings that tillage may disrupt the vertical continuity of macropore clusters. The impact of liming on soil pore network properties may have been limited to pores smaller than the resolution in our X‐ray images. It is also possible that the effects of lime on soil structure were limited to a few years which means that any effect would have diminished by the time of this study. These matters should be further investigated in follow‐up studies to understand better the potential of lime amendments to clay soil.

Curved Fragmented Graphenic Hierarchical Architectures for Extraordinary Charging Capacities.

An approach to assemble hierarchically ordered 3D arrangements of curved graphenic nanofragments for energy storage devices is described. Assembling them into well-defined interconnected macroporous networks, followed by removal of the template, results in spherical macroporous, mesoporous, and microporous carbon microball (3MCM) architectures with controllable features spanning nanometer to micrometer length scales. These structures are ideal porous electrodes and can serve as lithium-ion battery (LIB) anodes as well as capacitive deionization (CDI) devices. The LIBs exhibit high reversible capacity (up to 1335 mAh g-1 ), with great rate capability (248 mAh g-1 at 20 C) and a long cycle life (60 cycles). For CDI, the curved graphenic networks have superior electrosorption capacity (i.e., 5.17 mg g-1 in 0.5 × 10-3 m NaCl) over conventional carbon materials. The performance of these materials is attributed to the hierarchical structure of the graphenic electrode, which enables faster ion diffusion and low transport resistance.

3D Printing of Hierarchical Porous Silica and α‐Quartz

AbstractThe ability to macroscopically shape highly porous oxide materials while concomitantly tailoring the porous network structure as desired by simple and environmentally friendly processes is of great importance in many fields. Here, a purely aqueous printing process toward deliberately shaped, hierarchically organized amorphous silica and the corresponding polycrystalline quartz analogues based on a direct ink writing process (DIW) is presented. The key to success is the careful development of the sol–gel ink, which is based on an acidic aqueous sol of a glycolated silane and structure‐directing agents. The resulting 3D (DIW) printed silica consists of a macroporous network of struts comprising hexagonally arranged mesopores on a 2D hexagonal lattice. Together with a printed porous superstructure on the millimeter scale, well‐defined pore sizes and shapes on at least three hierarchy levels can thus be fabricated. The introduction of devitrifying agents in the printed green part and subsequent heat treatment allows for the transformation of the silica structure into polycrystalline α‐quartz. While small pores (micro‐ and mesopores below 10 nm) are lost, the printed morphology and the macroporous network of struts is preserved during crystallization.

Superelastic and pH-Responsive Degradable Dendrimer Cryogels Prepared by Cryo-aza-Michael Addition Reaction

Dendrimers exhibit super atomistic features by virtue of their well-defined discrete quantized nanoscale structures. Here, we show that hyperbranched amine-terminated polyamidoamine (PAMAM) dendrimer G4.0 reacts with linear polyethylene glycol (PEG) diacrylate (575 g/mol) via the aza-Michael addition reaction at a subzero temperature (−20 °C), namely cryo-aza-Michael addition, to form a macroporous superelastic network, i.e., dendrimer cryogel. Dendrimer cryogels exhibit biologically relevant Young’s modulus, high compression elasticity and super resilience at ambient temperature. Furthermore, the dendrimer cryogels exhibit excellent rebound performance and do not show significant stress relaxation under cyclic deformation over a wide temperature range (−80 to 100 °C). The obtained dendrimer cryogels are stable at acidic pH but degrade quickly at physiological pH through self-triggered degradation. Taken together, dendrimer cryogels represent a new class of scaffolds with properties suitable for biomedical applications.

Controlled network structures of chitosan-poly(ethylene glycol) hydrogel microspheres and their impact on protein conjugation

We demonstrate a facile approach to manufacture hydrogel microspheres with controlled and macroporous network structures via a simple yet versatile micromolding-based technique. Specifically, highly uniform poly(ethylene glycol) (PEG) hydrogel microspheres containing chemically functional chitosan are readily fabricated using the micromolding-based technique that utilizes surface tension-induced droplet formation of aqueous prepolymer solution followed by photo-induced interfacial polymerization. Network structures of the hydrogel microspheres are readily controlled by simple addition of inert porogen, which induces phase separation during the polymerization. Fluorescent labeling studies reveal tunable distribution of the chitosan within the PEG networks (i.e., uniform and core-shell like distributions) depending on the content of the porogen in the prepolymer solution. In addition, protein conjugation studies show tunable pore sizes and 3D network structures by adjusting content of the porogen, and formation of macroporous networks leading to significantly improved protein conjugation kinetics. The macroporous network structures are further supported with scanning electron microscopy (SEM) results that correspond well with confocal microscopy results. We believe that our fabrication strategy offers a simple and robust route to construct diverse 3D hydrogel network structures with chemical functionality, enabling production of a variety of biofunctionalized hydrogel microspheres that can be utilized in various biomedical applications.