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Item type:Publication, Access status: with files , Hydrogel particles under uniaxial compression: Tetrapod-based DEM approach and experimental validation(Elsevier, 2026-08-26); ; ; ; Hydrogels are soft, water-rich polymer networks whose mechanical behavior governs applications ranging from biomedicine to packed bed processes. In aerogel manufacturing, hydrogel particles represent an intermediate state in which mechanical stability determines scalability and process reliability. However, predictive particle-scale models for deformable matrix-fluid systems remain limited. Biopolymer-based hydrogel particles are investigated under uniaxial compression through monotonic, cyclic, and stress-relaxation experiments at compression rates of 0.1–3.0 mm/s. Apparent stiffness increased strongly with rate, followed by saturation above 0.5 mm/s, where the apparent Young’s modulus became rate independent. Within the elastic regime, the response is reproducible and hysteretic, whereas higher strains induced plastic deformation. Aging over one year led to additional stiffening, indicating ongoing structural evolution. To complement the experiments, a novel discrete-element-method framework based on tetrapod-shaped parcels is introduced. Tetrapods qualitatively represent the 3D polymer network and predominantly carry mechanical loads, while embedded spheres mimic the aqueous phase. Parameters are calibrated using a full-factorial design and Bayesian optimization. Simulations reproduce the force–strain response, apparent elastic properties, and particle deformation. Random packings produce comparable scatter, while stress relaxation and cyclic loading are reproduced qualitatively. The approach advances predictive modeling of deformable particles and provides a basis for solvent exchange and process-scale simulations.Publicationtype: Journal Article25 37 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Properties of agar aerogels: effect of concentration and ageing time(Elsevier, 2026-06-01); ; ; ; Agar, a polysaccharide derived from red algae, is a renewable, edible, and biocompatible hydrocolloid with excellent gelling properties. Although widely used in the food industry and microbiology, its potential for advanced material design, particularly as an aerogel, has not yet been sufficiently explored. In this study, agar aerogels were produced via the sol-gel process and supercritical CO2 drying. The effects of polysaccharide concentration (2%, 6%, and 10% w/v) and ageing time (24 h and 10 days) on the structural, textural and compressive mechanical properties were systematically investigated for the first time. All aerogels were highly porous, with specific surface areas reaching a maximum of 375 m2/g at a moderate agar concentration (6% w/v). Prolonged ageing generally improved the textural and morphological properties but reduced the compression strength and swelling capacity. All samples showed excellent water uptake and remained stable in aqueous environments for four weeks. These results demonstrate that both concentration and ageing time significantly affect the final performance of the agar aerogels. Their properties can be easily adjusted by processing parameters, offering great potential for biomedical, food-related, or environmental applications.Publicationtype: Journal Article25 41 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Production and characterization of bioaerogel particles from strawberries and their application as oil structuring ingredient in low-saturated fat cocoa spreads(Elsevier, 2025-05-17); ; ; ; Bioaerogels bear high potential in the development of fat-replacers, due to their oil-structuring capacity. However, current aerogel preparation from biopolymeric gels requires a complex and resource-intensive processes, which might limit their adoption as oil-structuring food ingredients. A simpler and more sustainable process to produce bioaerogels could be based on their direct preparation from plant tissues rather than from biopolymeric gels. Similar to gels, also in plant tissues, water is embedded into a fibrous network, so water removal while preserving tissue structure can lead to porous materials with bioaerogel properties, avoiding biopolymer extraction, purification and sol-gel steps. This work aimed to demonstrate the potential of tissue-derived aerogels as fat-replacement ingredients in cocoa spreads. To this aim, strawberry pulp was subjected to water-to-ethanol exchange, wet milling, and supercritical-CO₂-drying. This process resulted in bioaerogel particles with high mesopore volume (0.69 cm3 g−1), low density (0.03 g cm−3) and high surface area (233 m2 g−1). The particles showed an oil absorption capacity higher than 90 %, leading to a plastic material retaining 80 % oil upon centrifugation. Strawberry bioaerogel particles were used to formulate low-saturated fat cocoa spreads. A bioaerogel particle amount as low as 0.2–0.4 g/100 gspread was enough to obtain spreads covering a wide range of rheological and spreadability properties. Preliminary techno-economic assessment demonstrated the technical and economic feasibility of the proposed process to produce bioaerogels from plant tissues intended as fat-replacement ingredients.Publicationtype: Journal Article107 22 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Conversion of natural tissues and food waste into aerogels and their application in oleogelation(Royal Society of Chemistry (RSC), 2025-04-04); ; ; ; In this work, various natural tissues were for the first time directly converted into nanostructured aerogels by utilizing their intrinsic (meso-)porosity. In contrast to common aerogel production, no use of pure biopolymers, their extraction, dissolution, gelation or use of additives (e.g. crosslinkers, acids and bases) was necessary. The production process required washing of the wet starting material with water, a solvent exchange with ethanol and drying with supercritical CO2. The resulting materials exhibited low bulk densities (0.01–0.12 g cm−3), significant specific surface areas (108–446 m2 g−1) and mesopore volumes (0.3–2.6 cm3 g−1). Assessment of 20 different tissues including fruit pulp and peel, vegetable pulp, and mushrooms showed the generality of the approach. A broad spectrum of different microstructures was identified, whereas especially textural properties of samples derived from water rich pulp were highly similar to those found in classical biopolymer aerogels, for instance based on pectin or cellulose. Furthermore, the capability of the materials to structure liquid sunflower oil was shown: the produced oleogels exhibited exceptionally high oil uptake (max. 99%) and rheological properties similar to those of solid fats. Results suggest that supercritical drying of tissues (e.g. based on food waste) is a suitable approach for their upcycling into value added materials by a complete green and sustainable process. This research also contributes to sustainable development by transforming food waste into valuable aerogels and promoting science education through accessible, open-source STEM resources.Publicationtype: Journal Article70 31 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Simulation-based characterization of alginate aerogel packed bed compaction via DEM-BPM(Elsevier, 2025-04); ; ; ; The global demand for aerogels is constantly growing, thus, optimizing and scaling up the production processes have become increasingly important in the last decade. The utilization of millimeter-sized aerogel particles for such purposes is typically preferred due to inherent advantages in handling and production compared to other geometries. The production of these particles is most commonly accomplished using a particle packed bed (autoclave). This process presents, however, several challenges, including the impact of mechanical loads on the quality of the product. Therefore, this work focuses on deepening the understanding of mechanical properties and deformation mechanisms of aerogel particles in packed beds under uniaxial compaction. The investigated alginate aerogel particles are characterized by a spherical shape (circularity of 0.96), a specific surface area of ~352 m2/g, an average diameter of ~3.3 mm, and a bulk density of ~0.05 g/cm3. In addition, this study extends a DEM-BPM model to capture the mechanical deformation of biopolymer aerogels, both as individual particles and within packed beds. The simulations were calibrated and validated using experimental data from uniaxial compaction tests. An optimization methodology was implemented to reduce reliance on traditional trial-and- error methods and improve the model’s accuracy. The results demonstrate that the proposed DEM-BPM model effectively replicates the mechanical behavior of alginate aerogels, showing strong agreement between experi- mental data and minimal deviations for both single particles and packed beds (R2≥ 0.93). This model serves as a promising tool for gaining deeper insights into the mechanical properties of aerogels and improving production efficiency. Additionally, the DEM-BPM model can be expanded to incorporate intermediate products, such as hydrogels and alcogels, enabling process optimization at every stage of aerogel manufacturing.Publicationtype: Journal Article49 29 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Lignin Polyurethane Aerogels: Influence of Solvent on Textural Properties(Multidisciplinary Digital Publishing Institute (MDPI), 2024-12-14); ; ; This study explores the innovative potential of native lignin as a sustainable biopolyol for synthesizing polyurethane aerogels with variable microstructures, significant specific surface areas, and high mechanical stability. Three types of lignin-Organosolv, Aquasolv, and Soda lignin-were evaluated based on structural characteristics, Klason lignin content, and particle size, with Organosolv lignin being identified as the optimal candidate. The microstructure of lignin polyurethane samples was adjustable by solvent choice: Gelation in DMSO and pyridine, with high affinity to lignin, resulted in dense materials with low specific surface areas, while the use of the low-affinity solvent e.g acetone led to aggregated, macroporous materials due to microphase separation. Microstructural control was achieved by use of DMSO/acetone and pyridine/acetone solvent mixtures, which balanced gelation and phase separation to produce fine, homogeneous, mesoporous materials. Specifically, a 75% DMSO/acetone mixture yielded mechanically stable lignin polyurethane aerogels with a low envelope density of 0.49 g cm-3 and a specific surface area of ~300 m2 g-1. This study demonstrates a versatile approach to tailoring lignin polyurethane aerogels with adjustable textural and mechanical properties by simple adjustment of the solvent composition, highlighting the critical role of solvent-lignin interactions during gelation and offering a pathway to sustainable, high-performance materials.Publicationtype: Journal Article48 78 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Transparent cellulose aerogels from concentrated salt solutions : synthesis and characterization(Wiley, 2024-08-29); ; ; In this work, nanostructured and transparent cellulose aerogels are synthesized via a purely salt induced approach from non‐modified microcrystalline cellulose type II. The production process requires in contrast to state of the art methods no pretreatment of cellulose or use of expensive cellulose‐solvents: it consists of hydrogel formation via cross‐linking of cellulose with calcium ions, a solvent exchange and a supercritical drying step. A systematic multiparameter study reveals that a high level of structural control is achievable: ratios of macro‐ to mesoporosity and the size of mesopores can be tailored by adjustment of the calcium ion content, while keeping a high overall porosity in the range of 92% – 96 %. The build‐up of homogeneous, fine pore structures results in a significant increase of the specific surface area as compared to conventional calcium‐free aerogels (684 vs. 300 m² g⁻¹). Remarkably, the Ca²⁺‐cross‐linking renders aerogels transparent, with Rayleigh scattering being the dominant scattering mechanism. Additional ion exchange to Ca²⁺ in the hydrogel‐state leads to further reduction of the pore size and to products with optimized optical properties, e.g., light transmission of 91% at an incidents light wavelength of 800 nm and a substrate thickness of 1.5 mm.Publicationtype: Journal Article109 77 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Hydrophobic aerogels from vinyl polymers derived from radical polymerization : proof of concept(Wiley, 2024-06-14); ; ; ; Hydrophilicity is one important drawback of bio-based aerogels. To overcome this issue, a novel approach for the preparation of mesoporous, water repellent aerogels is introduced, which combines synthesis of crosslinked bio-based copolymers from methacrylate copolymerizations, followed by solvent exchange and supercritical drying steps. The influence of monomers with different non-polar ester groups (methyl, vanillin, tetrahydrofurfuryl) on textural properties and water contact angles of the dry products is assessed. Final aerogels show generally high overall porosities (∼ 96%), low densities (0.07 – 0.11 g cm−3) as well as fine, mainly mesoporous networks, and specific surface areas in the range of 120 – 240 m2 g−1. Hereby, choice of the methacrylate ester groups results in differences of the resulting pore-size distributions. Water repellency tests show stable static water contact angles in the hydrophobic range (∼ 100 °) achieved for the substrate containing the vanillin ester group. On the contrary the other substrates absorb water quickly, which indicates a decisive role of the ester group. The presented approach opens up a new pathway to bio-based aerogels with intrinsic hydrophobicity. It is suggested that the properties are tailored by the choice of the monomer structure, hence enabling further adaption and optimization of the products.Publicationtype: Journal Article40 76 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Natural grown aerogels from fruits, vegetables and mushrooms : processing and characterization(2022-09); ; ; ; Aerogels are highly porous materials with special properties like a high specific surface area up to 1200 m2 g-1 and low densities of approx. 0.1 g cm-3. Especially biopolymer aerogels (e.g. alginate, chitosan and cellulose) are used due to their high availability, biocompatibility and non-toxicity. The applications of these mesoporous materials are in fields of carrier matrices (food and pharma), thermal insulation and catalyst scaffolds. Biopolymer aerogel production requires a gelation step, in which the porous network is formed. Gelation is normally carried out in aqueous phase and can be induced via different methods (e.g. change of temperature, pH, addition of ions, etc.), followed by solvent exchange and supercritical drying. Fruits, vegetables, mushrooms and derived plant based food waste show internal three-dimensional pore networks formed by natural growth. Therefore, they can be converted into aerogel-like systems, without requiring a gelation step. The importance of sustainable processes in the (food) industry is growing steadily. In addition to energy efficiency and resource management, this also includes the recycling of food waste and by-products. Hence, the development of an alternative recycling method of food waste to natural grown aerogels is a promising solution to meet the economic requirements. The aim of this work is to provide an overview of different natural grown aerogels, which are produced based on their naturally aqueous state by solvent exchange with ethanol and supercritical drying at suitable conditions (40 °C and 100 bar). Furthermore, the aerogel-like morphology of supercritical dried fruits and vegetables is characterized. For this purpose, experimental investigations are performed related to the specific surface area (BET method), internal mesoporous structure (SEM pictures), density and volumetric shrinkage during the manufacturing process.Publicationtype: Conference Poster not in Proceedings179 123 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Inspiring for chemical and biochemical engineering : digitally, interactively, and hands‐on(Wiley-VCH, 2022); ; ; ; Publicationtype: Journal Article80