Scientific publications

The energy transition and the intermittent characteristic of renewable energy sources highlight the importance of materials research for energy storage systems. Hexacyanometalates (HCM) are promising candidates in energy storage systems due to their structure, capability of intercalating/extracting ions during the redox process, and the variety of synthesis techniques available. Among HCMs, nickel hexacyanoferrate (NiHCF) gains attention due to its long-life cycle and promising application in aqueous systems. Combining the properties of NiHCF along with freestanding films based on reduced graphene oxide (rGO) and polyaniline (PAni) offers a promising application in aqueous batteries as it includes both the electroactive material and the current collector in a single electrode. Herein, freestanding electrodes based on rGO/PAni/NiHCF are synthesized through the electrodeposition of NiHCF over rGO/PAni films, enabling control of the amount of NiHCF nanoparticles and the freestanding film thickness. Thinner electrodes achieve specific capacity values of 83 mAh g−1 at the current density of 50 mA g−1 in a three-electrode system, a specific capacity close to 61 mAh g−1 at the current density of 10 mA g−1 in a coin-cell system, approaching the theoretical capacity of NiHCF.

Endothelial cells (ECs) experience shear stress associated with blood flow. Such shear stress regulates endothelial function by altering cell physiology. Since most cell culture protocols and media compositions are designed for static cultures and experiments with ECs are predominantly conducted under these non-physiological conditions, a model for culturing ECs under flow conditions is developed, which more closely mimics their physiological environment. This approach also enables the isolation of EVs while minimizing FCS-derived contaminants. In this study, a comprehensive assessment of how physiologically relevant cultivation conditions influence the vesicle composition and function of ECs is provided. A detailed investigation is conducted for the effect of different cell culture media on morphology and marker expression of human umbilical cord endothelial cells (HUVECs) and EVs, and optimize the conditions to culture ECs under flow, tailoring them specifically to facilitate the efficient isolation of EVs using a hollow-fiber system model. These EVs are then characterized and compared to those isolated from traditional static culture conditions. Overall, this study presents a model on isolating EC-derived EVs under conditions that closely mimic physiological environments, and characterization at their proteome, gene expression, and microRNA profile.

Glaucoma, an eye disease causing incremental vision loss, currently has no cure. Its primary cause is the malfunction of the trabecular meshwork (TM), a multilayered tissue in the eye responsible for draining aqueous humor (AH) from the anterior chamber. TM clogging increases outflow resistance, elevates intraocular pressure (IOP), and damages optic nerves, leading to irreversible blindness. Existing in vitro TM models are suboptimal, as they lack the hierarchical structure of the TM. This article introduces a dynamic in vitro TM model, featuring a multilayered scaffold architecture 3D printed via melt electrowriting (MEW), and integrated with a flow system that enables continuous pressure monitoring during perfusion at native flow rates. Printed scaffolds supported the growth of primary adult human TM cells that grew on top and between the fibers. Cellularized scaffolds were tested under static and dynamic conditions. Over 3–5 days, pressure monitoring showed increased outflow resistance due to cell proliferation. Proteomic analysis revealed distinct changes in protein expression related to protein synthesis and respiration of cells grown under flow. Lat-B administration resulted in decreased pressure values and depolymerized actin filaments. These findings suggest that the proposed model is a promising alternative for in vitro glaucoma drug testing.

The potential of bioactive coatings as an innovative biotechnology to overcome the mass-transfer limitations of conventional technologies when treating air pollutants, especially hydrophobic volatile organic compounds, was herein assessed. Bioactive coatings consist of active microorganisms entrapped in a polymer matrix, which needs to be porous to facilitate an effective gas pollutant exchange. To increase porosity, two additives, sucrose and glycerol mixtures (Suc/Gly) and halloysite nanotubes (HNTs), were included in the bioactive coatings at two concentration levels. The toluene removals of the different bioactive coatings were studied in batch mode at low (∼300 mg m−3) and high (∼3000 mg m−3) toluene concentrations. Overall, low HNTs concentration coatings supported optimum toluene removals (>95 %), comparable to biofilm controls at both toluene concentrations. High HNTs concentration coatings and low Suc/Gly concentration coatings achieved toluene removals over 95 % after 7 toluene injections at low toluene concentration. At high toluene concentrations, these coatings eventually outperformed the biofilm controls. High Suc/Gly concentration coatings supported a limited toluene removal (4 and 1 injection at low and high toluene concentrations, respectively), attributed to a preferential consumption of sucrose over toluene. These findings were corroborated by ESEM/conventional SEM imaging, revealing porosity in the HNTs bioactive coatings, visible at both the surface and internal levels. On the contrary, more homogeneous surfaces were observed in the Suc/Gly bioactive coatings, where total polymer coalescence was partially hindered by the addition of Suc/Gly. These results paved the way towards the implementation of bioactive coating in larger bioreactors for real-life air purification.

Conductive polymer composites (CPCs) combine the stretchability of an elastomeric matrix with the electrical conductivity of a metallic filler. The 3D structure of this filler particle network (FPN) and the contact resistances between particles above percolation, key factors in the conductivity, are not well understood. Here, we introduce 3D reconstructions of FPNs of micron-sized spherical silver particles in polydimethylsiloxane from focused ion beam scanning electron microscopy tomography. Analysis of the tomographic images provides the length and number of parallel conductive paths. The results show that the average contact resistance drops five orders of magnitude when increasing the silver loading from 36 vol% to 53 vol%, highlighting its dominating role for macroscopic conductivity rather than network structure. This links to 33% larger average area-equivalent diameters of the contact spots. Diffusional tortuosity, a metric that quantifies flow restriction through narrow contact spots, proves that higher contact forces decrease current flow restrictions and thus, increase overall electrical conductivity. These conclusions are verified using a segregated CPC, and it is found that the addition of 20 vol%
of insulating fillers at a constant silver loading of 30 vol% increases the conductivity 37-fold and decreases the average contact resistance by two orders of magnitude.

Individuals with more elastic, more hydrated or smaller fingers usually show better performance in several passive touch tasks. In active touch, people use different exploratory procedures when evaluating object properties, and tune their exploratory parameters. For example, they indent stimuli to assess softness and optimize their peak forces to get relevant information. In this study, we aim to understand whether finger pad size, elasticity and hydration affect individuals' force-tuning and discrimination performance in active softness perception. Participants performed two softness tasks in two different sessions. In one session, hyaluronic acid was applied to their finger pads to soften it, in the other they received no treatment. We assessed individual elasticity and hydration values with cutometer and corneometer in each session, and measured finger pad size in three dimension by caliper. In each task, two pairs of stimuli were presented to the participants (Young's Modulus: 41.5 vs. 45.0; 28.7 vs. 31.3 kPa) who chose the softer stimulus. In the restricted task, they could apply force only up to 2 Newton, whereas there was no force limit in the unconstrained task. We found that participants with smaller finger pad size exerted less force in the restricted task and participants with more hydrated and elastic fingers exerted less force in the unconstrained task. The force-tuning disappeared in the unconstrained task when treatment was applied. These results indicate that people employ strategies according to their finger parameters and to the availability of cues whereas adaptation to treatment is likely to need longer practice.

Plant-inspired soft robots enable distributed environmental monitoring. Fliers, i.e. soft robots that are carried passively by the wind, can be effectively deployed and cover large areas and distances. State-of-the-art fliers for humidity sensing are largely composed of electronic components, which increase cost and generate electronic waste. Here, we introduce self-deployable and biodegradable fliers inspired by natural Ailanthus altissima seeds. These artificial fliers are composed of fluorescent, cellulose-based composites with sensing capabilities. The material is shaped into artificial seeds using scalable 3D extrusion processing. Red-emitting Mn2+-doped Er3+, Yb3+:NaYF4 nanoparticles in the composite provide a strong optical emission upon excitation at 980 nm wavelength. The cellulose matrix absorbs water, which quenches the intensity of fluorescence of the nanoparticles. Increasing humidity thus changes the color of the fluorescence emission from red to green. We used ratiometric sensing to detect the humidity of the surroundings.

Friction was studied for the human finger pad during the spreading of viscous liquid samples in circular motion on a solid substrate. The samples included both Newtonian and shear-thinning liquids with a range of viscosity between 0.83 mPa s and 150 Pa s. During active touch, participants applied varying normal forces and sliding speeds depending on the sample and individual behavior. Friction coefficients vary greatly between participants, but fall on one Stribeck curve when shear-thinning effects were accounted for full-film lubrication. A comparison with the measured height variations during spreading demonstrates that the logarithm of the Hersey number is an instantaneous indicator of the film thickness in the full-film lubrication regime. Comparison of the measured friction coefficients with reported values of the perceived slipperiness for the same samples shows a close correspondence along the Stribeck curve.

Selenium sulfide, the active ingredient of traditional antidandruff shampoos, is industrially produced from selenium dioxide (SeO2) and hydrogen sulfide (H2S) under acidic conditions. This reaction can also be carried out with natural H2S and H2S generated by sulfate-reducing bacteria (SRB). These bacteria are robust and, by relying on their conventional growth medium, also thrive in “waste” materials, such as a mixture of cabbage juice and compost on the one side, and a mixture of spoiled milk and mineral water on the other. In these mixtures, SRB are able to utilize the DL-lactate and sulfate (SO42−) present naturally and produce up to 4.1 mM concentrations of H2S in the gas phase above a standard culture medium. This gas subsequently escapes the fermentation vessel and can be collected and reacted with SeO2 in a separate compartment, where it yields, for instance, pure selenium sulfide, therefore avoiding the need for any cumbersome workup or purification procedures. Thus “harvesting” H2S and similar (bio-)gases produced by the fermentation of organic waste materials by suitable microorganisms provides an elegant avenue to turn dirty waste into valuable clean chemical products of considerable industrial and pharmaceutical interest. © 2025 by the authors.

With rising demand for lithium-ion batteries, efficient recycling is crucial. While conventional methods face cost and environmental challenges, electrochemical recovery offers a sustainable and energy-efficient alternative. In this study, we investigate the electrochemical recovery of lithium-ions from spent lithium iron phosphate batteries using carbon-coated lithium iron phosphate electrodes, with a focus on the influence of pH adjustment and competing ion effects. Our results demonstrate that NaOH-adjusted electrolytes provide the highest lithium-ion recovery efficiency, with an average removal capacity of 18 mgLi gLFP−1 over 50 cycles. However, prolonged cycling leads to capacity fading, particularly in the presence of competing cations such as Na+ and K+, which impact lithium selectivity and electrode stability. These findings underscore the importance of optimizing electrolyte conditions and electrode materials to enhance long-term performance. Future research should explore alternative pH control strategies and scalable process designs to facilitate industrial implementation. Advancing electrochemical lithium-ion recovery aligns with broader sustainability goals, offering a viable route toward circular battery recycling and reduced environmental impact.