INMdok (Leibniz Institute for New Materials)
Not a member yet
931 research outputs found
Sort by
Digital research data: from analysis of existing standards to a scientific foundation for a modular metadata schema in nanosafety
Get PDFAssessing the safety of engineered nanomaterials (ENMs) is an interdisciplinary and complex process producing huge amounts of information and data. To make such data and metadata reusable for researchers, manufacturers, and regulatory authorities, there is an urgent need to record and provide this information in a structured, harmonized, and digitized way. RESULTS: This study aimed to identify appropriate description standards and quality criteria for the special use in nanosafety. There are many existing standards and guidelines designed for collecting data and metadata, ranging from regulatory guidelines to specific databases. Most of them are incomplete or not specifically designed for ENM research. However, by merging the content of several existing standards and guidelines, a basic catalogue of descriptive information and quality criteria was generated. In an iterative process, our interdisciplinary team identified deficits and added missing information into a comprehensive schema. Subsequently, this overview was externally evaluated by a panel of experts during a workshop. This whole process resulted in a minimum information table (MIT), specifying necessary minimum information to be provided along with experimental results on effects of ENMs in the biological context in a flexible and modular manner. The MIT is divided into six modules: general information, material information, biological model information, exposure information, endpoint read out information and analysis and statistics. These modules are further partitioned into module subdivisions serving to include more detailed information. A comparison with existing ontologies, which also aim to electronically collect data and metadata on nanosafety studies, showed that the newly developed MIT exhibits a higher level of detail compared to those existing schemas, making it more usable to prevent gaps in the communication of information. CONCLUSION: Implementing the requirements of the MIT into e.g., electronic lab notebooks (ELNs) would make the collection of all necessary data and metadata a daily routine and thereby would improve the reproducibility and reusability of experiments. Furthermore, this approach is particularly beneficial regarding the rapidly expanding developments and applications of novel non-animal alternative testing methods
Precipitate number density determination in microalloyed steels by complementary atom probe tomography and matrix dissolution
Get PDFParticle number densities are a crucial parameter in the microstructure engineering of microalloyed steels. We introduce a new method to determine nanoscale precipitate number densities of macroscopic samples that is based on the matrix dissolution technique (MDT) and combine it with atom probe tomography (APT). APT counts precipitates in microscopic samples of niobium and niobium-titanium microalloyed steels. The new method uses MDT combined with analytical ultracentrifugation (AUC) of extracted precipitates, inductively coupled plasma–optical emission spectrometry, and APT. We compare the precipitate number density ranges from APT of 137.81 to 193.56 × 1021 m−3 for the niobium steel and 104.90 to 129.62 × 1021 m−3 for the niobium-titanium steel to the values from MDT of 2.08 × 1021 m−3 and 2.48 × 1021 m−3. We find that systematic errors due to undesired particle loss during extraction and statistical uncertainties due to the small APT volumes explain the differences. The size ranges of precipitates that can be detected via APT and AUC are investigated by comparison of the obtained precipitate size distributions with transmission electron microscopy analyses of carbon extraction replicas. The methods provide overlapping resulting ranges. MDT probes very large numbers of small particles but is limited by errors due to particle etching, while APT can detect particles with diameters below 10 nm but is limited by small-number statistics. The combination of APT and MDT provides comprehensive data which allows for an improved understanding of the interrelation between thermo-mechanical controlled processing parameters, precipitate number densities, and resulting mechanical-technological material properties
Ionophobicity of carbon sub-nanometer pores enables efficient desalination at high salinity
Get PDFSummary Electrochemical seawater desalination has drawn significant attention as an energy-efficient technique to address the global issue of water remediation. Microporous carbons, that is, carbons with pore sizes smaller than 2 nm, are commonly used for capacitive deionization. However, micropores are ineffective for capacitive deionization at high molar strength because of their inability to permselectively uptake ions. In our work, we combine experimental work with molecular dynamics simulation and reveal the ability of sub-nanometer pores (ultramicropores) to effectively desalinate aqueous media at seawater-like molar strength. This is done without any ion-exchange membrane. The desalination capacity in 600 mM reaches 12 mg/g, with a charge efficiency of 94% and high cycling stability over 200 cycles (97% of charge efficiency retention). Using molecular dynamic simulations and providing experimental data, our work makes it possible both to understand and to calculate desalination capacity and charge efficiency at high molar strength as a function of pore size
Emerging, hydrogen-driven electrochemical water purification
Get PDFEnergy-efficient technologies for the remediation of water and generation of drinking water is a key towards sustainable technologies. Electrochemical desalination technologies are promising alternatives towards established methods, such as reverse osmosis or nanofiltration. In the last few years, hydrogen-driven electrochemical water purification has emerged. This review article explores the concept of desalination fuel cells and capacitive-Faradaic fuel cells for ion separation
Time-Dependent Cation Selectivity of Titanium Carbide MXene in Aqueous Solution
Get PDFElectrochemical ion separation is a promising technology to recover valuable ionic species from water. Pseudocapacitive materials, especially 2D materials, are up-and-coming electrodes for electrochemical ion separation. For implementation, it is essential to understand the interplay of the intrinsic preference of a specific ion (by charge/size), kinetic ion preference (by mobility), and crystal structure changes. Ti3C2Tz MXene is chosen here to investigate its selective behavior toward alkali and alkaline earth cations. Utilizing an online inductively coupled plasma system, it is found that Ti3C2Tz shows a time-dependent selectivity feature. In the early stage of charging (up to about 50 min), K+ is preferred, while ultimately Ca2+ and Mg2+ uptake dominate; this unique phenomenon is related to dehydration energy barriers and the ion exchange effect between divalent and monovalent cations. Given the wide variety of MXenes, this work opens the door to a new avenue where selective ion-separation with MXene can be further engineered and optimized
Flexible and transparent electrodes imprinted from metal nanostructures: morphology and opto-electronic performance
Get PDFWe directed the self-assembly of nanoscale colloids via direct nanoimprint lithography to create flexible transparent electrodes (FTEs) with metal line widths below 3 μm in a roll-to-roll-compatible process. Gold nanowires and nanospheres with oleylamine shells were imprinted with soft silicone stamps, arranged into grids, and converted into metal lines in a plasma process. We studied the hierarchical structure and opto-electronic performance of the resulting grids as a function of particle geometry and concentration. The performance in terms of optical transmittance was dominated by the line width. Analysis of cross-sections indicated that plasma sintering only partially removed the insulating ligands and formed lines with thin conductive shells and a non-conductive core. We provide evidence that the self-assembly of high-aspect nanowires can compensate for defects of the stamp and substrate irregularities during imprinting, while spheres cannot. The wire-based electrodes thus outperformed the sphere-based electrodes at ratios of optical transmittance to sheet resistance of up to ≈ 0.9 %·Ωsq-1, while spheres only reached ≈ 0.55 %·Ωsq-1
Interacting particles in an activity landscape
Get PDFWe study interacting active Brownian particles (ABPs) with a space-dependent swim velocity via simulation and theory. We find that, although an equation of state exists, a mechanical equilibrium does not apply to ABPs in activity landscapes. The pressure imbalance originates in the flux of polar order and the gradient of swim velocity across the interface between regions of different activity. An active–passive patch system is mainly controlled by the smallest global density for which the passive patch can be close packed. Below this density a critical point does not exist and the system splits continuously into a dense passive and a dilute active phase with increasing activity. Above this density and for sufficiently high activity the active phase may start to phase separate into a gas and a liquid phase caused by the same mechanism as motility-induced phase separation of ABPs with a homogeneous swim velocity
Melt Electrowriting of Graded Porous Scaffolds to Mimic the Matrix Structure of the Human Trabecular Meshwork
Get PDFThe permeability of the human trabecular meshwork (HTM) regulates eye pressure via a porosity gradient across its thickness modulated by stacked layers of matrix fibrils and cells. Changes in HTM porosity are associated with increases in intraocular pressure and the progress of diseases such as glaucoma. Engineered HTMs could help to understand the structure–function relation in natural tissues and lead to new regenerative solutions. Here, melt electrowriting (MEW) is explored as a biofabrication technique to produce fibrillar, porous scaffolds that mimic the multilayer, gradient structure of native HTM. Poly(caprolactone) constructs with a height of 125–500 μm and fiber diameters of 10 –12 μm are printed. Scaffolds with a tensile modulus between 5.6 and 13 MPa and a static compression modulus in the range of 6 –360 kPa are obtained by varying the scaffold design, that is, the density and orientation of the fibers and number of stacked layers. Primary HTM cells attach to the scaffolds, proliferate, and form a confluent layer within 8–14 days, depending on the scaffold design. High cell viability and cell morphology close to that in the native tissue are observed. The present work demonstrates the utility of MEW for reconstructing complex morphological features of natural tissues
A bioinspired snap-through metastructure for manipulating micro-objects
Get PDFMicro-objects stick tenaciously to each other—a well-known show-stopper in microtechnology and in handling micro-objects. Inspired by the trigger plant, we explore a mechanical metastructure for overcoming adhesion involving a snap-action mechanism. We analyze the nonlinear mechanical response of curved beam architectures clamped by a tunable spring, incorporating mono- and bistable states. As a result, reversible miniaturized snap-through devices are successfully realized by micron-scale direct printing, and successful pick-and-place handling of a micro-object is demonstrated. The technique is applicable to universal scenarios, including dry and wet environment, or smooth and rough counter surfaces. With an unprecedented switching ratio (between high and low adhesion) exceeding 104, this concept proposes an efficient paradigm for handling and placing superlight objects. Nature teaches us how to design reliable grippers for moving and placing super-small objects that tend to stick to everywhere
Permselective and ion-selective carbon nanopores and next-generation technologies for electrochemical water treatment
Get PDFOwing to an expanding economy and growing population, there is increasing consumer demand for freshwater. However, with global climate change and water pollution issues, there is rising water stress in many countries worldwide. Electrochemical water desalination technologies such as capacitive deionization (CDI) utilize electrical energy to store ions in porous materials and provide energy-efficient water desalination. However, due to the cation and anion exchange process during the charging and discharging processes, CDI is considered suitable for low salinity water desalination (salinity of 1-10 g/L). This dissertation explores novel approaches to next-generation CDI for better desalination performances and water desalination at high ionic strength. In particular, the ability of sub-nanometer carbon pores (ultramicropores) to enable highly efficient CDI even at seawater salinity is demonstrated based on unexpected simulation predictions. This unique ability originates from the energy barrier of ion solvation for pores smaller than the solvation shell. Consequently, uncharged carbon ultramicropores behave ionophobic and overcome the limitation of CDI only to be suitable for remediation of brackish water. Ultramicropores also provide novel perspectives for ion separation via the interplay of intrinsic and kinetic ion selectivity. This work also establishes electrocatalytic fuel cell desalination, whereby conventional fuel cell technology can easily be adapted to generate electricity, heat, and desalinated water concurrently.Als Resultat der boomenden Wirtschaft und dem weltweiten Bevölkerungswachstum steigt auch der Bedarf an Süßwasser stetig an. Angesichts des globalen Klimawandels und der vorherrschenden Wasserverschmutzung ist die Wasserknappheit längst nicht mehr nur auf einzelne Regionen begrenzt, sondern herrscht bereits in vielen Ländern auf der ganzen Welt vor. Elektrochemische Wasserentsalzungstechnologien wie die kapazitive Deionisation (CDI) nutzen elektrische Energie, um Ionen in porösen Materialien zu speichern und bieten somit die Grundlage für eine energieeffiziente Technologie zur Wasserentsalzung. Aufgrund des Kationen- und Anionenaustausches während des Lade- und Entladevorgangs ist die CDI jedoch nur für die Entsalzung von Brackwasser (Salinität von 1 bis 10 g/L) geeignet. In der vorliegenden Dissertationsschrift werden neue Ansätze für die nächste Generation an CDI zur Verbesserung der Entsalzungsleistung sowie der Wasserentsalzung bei hoher Ionenstärke untersucht. Insbesondere wird auch anhand unerwarteter Simulationsvorhersagen gezeigt, dass Kohlenstoffporen im Subnanometerbereich (Ultramikroporen) eine hocheffiziente CDI selbst beim Salzgehalt von Meerwasser ermöglichen. Diese einzigartige Fähigkeit ergibt sich aus der Energiebarriere der Ionensolvatation für Poren, die kleiner sind als die Solvatationsschale. Folglich verhalten sich ungeladene Kohlenstoff-Ultramikroporen ionophob und überwinden die Beschränkung der CDI, so dass sie für die Aufarbeitung von Brackwasser geeignet sind. Ultramikroporen bieten zusätzlich neue Perspektiven für die Ionentrennung durch das Zusammenspiel von intrinsischer und kinetischer Ionenselektivität. Mit dieser Arbeit wird ebenfalls die elektrokatalytische Brennstoffzellenentsalzung eingeführt, wobei die herkömmliche Brennstoffzellentechnologie leicht angepasst werden kann, um gleichzeitig Strom, Wärme und entsalztes Wasser zu erzeugen