The European GAIA project focussed on the development of novel ionomer, membrane, reinforcement, catalyst, catalyst support, gas diffusion and microporous layers, and layer constructions for high power density, high current density automotive membrane electrode assemblies (MEAs). Reaching a sufficiently low degradation rate (11-14 µV/h in an automotive drive cycle including operation at 105 °C) consistent with the 6,000 hour lifetime target while also succeeding in achieving the 1.8 W/cm2 power density at high current density (3 A/cm2) target was a major challenge, and the outcomes of GAIA represent an important step forward for fuel cell transport MEA technology. The results are all the more important that they were obtained with MEAs using materials developed and up-scaled in GAIA. By reaching this high-power density without increasing platinum loading, the Pt-specific power density was reduced to 0.25 g Pt/kW. Costs analysis demonstrated that recycling (catalyst and ionomer) has the potential to significantly reduce MEA cost, and that, with this, the cost per kW of the high power density GAIA MEAs approaches the 6 €/kW target. This presentation will outline the main materials development steps, summarise testing protocols and the results of automotive size cell short stack tests. Acknowledgement. This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under grant agreement n°826097. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research.

Background: During the coronavirus disease 2019 (COVID-19) pandemic face masks grew in importance as their use by the general population was recommended by health officials in order to minimize the risk of infection and prevent further spread of the virus. To ensure health protection of medical personnel and other system relevant staff, it is of considerable interest to quickly test if a certain lot of filtering facepiece masks meets the requirements or if the penetration changes under different conditions. As certified penetrometers are rather expensive and were difficult to obtain during the COVID-19 pandemic, we describe two quite simple and cheap methods to quickly test the filter penetration based on an electronic cigarette. Methods: The first method uses a precision scale, the second method uses a light scattering detector to measure the filter penetration. To make sure these two methods yield reliable results, both were tested with freshly cut filter samples covering the range of approx. 2 % to 60 % filter penetration and compared to the results of a certified penetrometer. Results: The comparison of the two methods with the certified penetrometer showed a good correlation and therefore allow a quick and rather reliable estimation of the penetration. Conclusions: Several examples about the use of faulty masks and the resulting health risks show that simple, fast, cheap and broadly available methods for filter characterization might be useful in these days.

Although nanomaterials are used in many fields, little is known about the fundamental interactions between nanomaterials and microorganisms. To test antimicrobial properties and retention ability, 13 electrospun polyamide (PA) nanomaterials with different morphology and functionalization with various concentrations of AgNO3 and chlorhexidine (CHX) were analyzed. Staphylococcus aureus CCM 4516 was used to verify the designed nanomaterials’ inhibition and permeability assays. All functionalized PAs suppressed bacterial growth, and the most effective antimicrobial nanomaterial was evaluated to be PA 12% with 4.0 wt% CHX (inhibition zones: 2.9 ± 0.2 mm; log10 suppression: 8.9 ± 0.0; inhibitory rate: 100.0%). Furthermore, the long-term stability of all functionalized PAs was tested. These nanomaterials can be stored at least nine months after their preparation without losing their antibacterial effect. A filtration apparatus was constructed for testing the retention of PAs. All of the PAs effectively retained the filtered bacteria with log10 removal of 3.3–6.8 and a retention rate of 96.7–100.0%. Surface density significantly influenced the retention efficiency of PAs (p ≤ 0.01), while the effect of fiber diameter was not confirmed (p ≥ 0.05). Due to their stability, retention, and antimicrobial properties, they can serve as a model for medical or filtration applications.

Electrospun polyamide (PA) nanofibers have great potential for medical applications (in dermatology as antimicrobial compound carriers or surgical sutures). However, little is known about microbial colonization on these materials. Suitable methods need to be chosen and optimized for the analysis of biofilms formed on nanofibers and the influence of their morphology on biofilm formation. We analyzed 11 PA nanomaterials, both nonfunctionalized and functionalized with AgNO3, and tested the formation of a biofilm by clinically relevant bacteria (Escherichia coli CCM 4517, Staphylococcus aureus CCM 3953, and Staphylococcus epidermidis CCM 4418). By four different methods, it was confirmed that all of these bacteria attached to the PAs and formed biofilms; however, it was found that the selected method can influence the outcomes. For studying biofilms formed by the selected bacteria, scanning electron microscopy, resazurin staining, and colony-forming unit enumeration provided appropriate and comparable results. The values obtained by crystal violet (CV) staining were misleading due to the binding of the CV dye to the PA structure. In addition, the effect of nanofiber morphology parameters (fiber diameter and air permeability) and AgNO3 functionalization significantly influenced biofilm maturation. Furthermore, the correlations between air permeability and surface density and fiber diameter were revealed. Based on the statistical analysis, fiber diameter was confirmed as a crucial factor influencing biofilm formation (p ≤ 0.01). The functionalization of PAs with AgNO3 (from 0.1 wt %) effectively suppressed biofilm formation. The PA functionalized with a concentration of 0.1 wt % AgNO3 influenced the biofilm equally as nonfunctionalized PA 8% 2 g/m2. Therefore, biofilm formation could be affected by the above-mentioned morphology parameters, and ultimately, the risk of infections from contaminated medical devices could be reduced.

The polymeric nanofibrous layers as a new material for possible improving dielectric properties and suppression of partial discharges in fiber/thermoset-matrix composites are introduced in this paper. Electrospun nanofibers made from polybenzimidazole (PBI) and polyimide (PI) were incorporated into the structure of the commonly used fiber/thermoset-matrix composites to enhance their dielectric behavior. PBI and PI were electrospun using a Nanospider laboratory scale machine. The spinning process was set to produce nanofibrous layers with two different areal weights (1 and 3 g.m−2 for composites with PBI and 3 and 5 g.m−2 for composites with PI). Control composites without nanofibers as well as composites containing electrospun PBI and PI nanofibrous layers were manufactured by compression molding in a laboratory press without any previous vacuum debulking. To verify the positive or negative influence of the incorporated nanofibrous layers on the overall dielectric behavior of the composites, the volume resistivity p (Ωm) and dielectric strength E d (kV.mm−1) were comprehensively measured. Initial results revealed that the volume resistivity of modified composites increased (of about 126 % for PBI and 217 % for PI) as well as the dielectric strength (of about 11 % for PBI and 53 % for PI). Obtained results were subsequently supported by partial discharge analysis which confirmed that the nanofibrous layers are capable to significantly suppress the partial discharge activity inside the composite structure.

The electrospun chitosan nanofibers provide excellent material for immobilized proteolytic enzymes, and are biocompatible, nontoxic and hydrophilic matrices with large specific area. This paper deals with an application of electrospun chitosan nanofibers and optimizing conditions for their biofunctionalization by model proteolytic enzyme trypsin. Nanofibers from chitosan were prepared using NanospiderTM technology and covalent immobilization of trypsin followed. Three immobilization techniques preserving biocompatibility and utilizing amine and/or hydroxyl groups of chitosan were optimized and compared to simple adsorption to achieve maximum proteolytic activity per cm2 of the functionalized chitosan nanofibers (Tryp-NF). Significant differences were observed. Trypsin immobilized by the carbodiimide one-step protocol demonstrated the highest activity of the three procedures, ranging from 132 to 210IU/cm2 (i.e., 548–874IU/mg of nanofibers), depending on the initial amount of trypsin used. Long-term storage stability together with high reusability of Tryp-NF confirmed advantages of the immobilized enzyme. Tryp-NF showed no cytotoxicity toward growth of HeLa cells. The in vivo tests for irritation and skin sensitization demonstrated no undesirable skin reactions.

A nanofibrous membrane carrier for nearly water insoluble drug diosmin was formulated. The aim of this study was to evaluate the drug release and dissolution properties in an aqueous buffer of pH 7.8, and to compare the suitability of the drug carrier with the available drug forms and screen diosmin absorption extent.The membranes were produced from HPC/PVA/PEO-drug water solutions and then evaluated by SEM and DSC measurements. The results showed that diosmin was incorporated within the nanofibers in an amorphous state, and/or as a solid dispersion. The results of in vitro release experiments excerpt a very fast release of the drug, followed by the formation of an over saturated solution and partial precipitation of the drug (a “spring” effect). The enormous increases in dissolution of the drug from a nanofibrous carrier, compared to a micronized and crystalline form, was achieved. The in vivo bioavailability study carried out on rats showed higher initial drug plasma levels and higher AUC values after administration of the nanofibrous drug formulation, compared to the micronized form. The results of the study demonstrated that the improvement of the diosmin in vitro dissolution also brought the enhanced in vivo absorption extent of the drug.

Various types of nanofibers are increasingly used in tissue engineering, mainly for their ability to mimic the architecture of tissue at the nanoscale. We evaluated the adhesion, growth, viability, and differentiation of human osteoblast-like MG 63 cells on polylactide (PLA) nanofibers prepared by needle-less electrospinning and loaded with 5 or 15 wt % of hydroxyapatite (HA) nanoparticles. On day 7 after seeding, the cell number was the highest on samples with 15 wt % of HA. This result was confirmed by the XTT test, especially after dynamic cultivation, when the number of metabolically active cells on these samples was even higher than on control polystyrene. Staining with a live/dead kit showed that the viability of cells on all nanofibrous scaffolds was very high and comparable to that on control polystyrene dishes. An enzyme-linked immunosorbent assay revealed that the concentration of osteocalcin was also higher in cells on samples with 15 wt % of HA. There was no immune activation of cells (measured by production of TNF-alpha), associated with the incorporation of HA. Moreover, the addition of HA suppressed the creep behavior of the scaffolds in their dry state. Thus, nanofibrous PLA scaffolds have potential for bone tissue engineering, particularly those with 15 wt % of HA.

The porous structure of electrospun TiO2 nanofibers was characterized in-depth and the best performing nanofiber structure for application in dye sensitized solar cell was identified. Four types of TiO2 nanofibers were investigated (electrospun from polyvinylpyrrolidone (PVP) and hydroxypropylcellulose (HPC) as templates) with diameters 100–280nm and surface areas 9–100m2/g. Mesoporous TiO2 films were prepared by supramolecular templating with a block copolymer Pluronic P123. For the preparation of composite nanofiber mesoporous films, 2% or 15% of electrospun nanofibers were added. Incorporation of nanofibers into the mesoporous film results in a decrease in dye N719 adsorption but at the same time in an increase of roughness factor. Solar efficiency of composite mesoporous films increases (unlike for pure mesoporous films) even for layer thickness higher than 2.3μm. Thus we developed a simplified method for the preparation of thick mesoporous nanofiber electrodes with improved solar efficiency of 5.51% which outperforms that of pure mesoporous film (4.96%).