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Eingeladener Vortrag
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Inspired by the chemistry of mussel adhesive proteins, polydopamine (PDA) is one of the simplest and most versatile approaches to confer new functionalities to nearly any material surface. Moreover, PDA exhibits high potential for surface modification and diversified secondary reactions that makes it extremely interesting for a wide range of application including biomedical field, e.g., drug delivery, adhesives, cell adhesion, biosensing. PDA has undergone significant expansion in its applications and is one of the most attractive areas within the materials field. Nevertheless, PDA integration in microdevices is still constrained by poor spatial and temporal control of excited deposition methods.
Herein, we demonstrate a novel maskless approach for PDA micropatterning based on Direct Laser Writing (DLW) that overcomes present limitations. The pattern is formed upon exposure of the dopamine solution by light produced by tightly-focused fs NIR laser that scans substrate surface accordingly to the selected pattern design. Neither strong oxidants, metal ions nor adjusting pH to alkaline is required by this technique. Our method achieves the PDA micropatterns with the spatial resolution of 0.8 µm, at least an order of magnitude smaller than what is possible with other PDA microplanning techniques. The here introduced PDA deposition technique will uniquely unravel applications of polydopamine and other catecholamine-based mussel-inspired materials in various multifunctional systems and microdevices (e.g., MEMS elements, microfluidics).
Adjustment of MPL parameters revealed that the morphology and thickness of resulted PDA microstructures can be controlled by altering the laser power and its scanning velocity. As a result, it also enables the production of micropatterns with structural gradient.
Apart from the glass substrate, we achieved PDA patterning at surfaces of different nature such as polychlorotrifluoroethylene, polydimethylsiloxane, polyethylene terephthalate, silicon wafers, and fluorinated glass coverslips.
The chemical nature of PDA was confirmed by locally recorded vibrational and x-ray photoelectron spectra. To ensure post-modification potential of MPL deposited PDA we demonstrated one-step deposition of micropatterns with trypsin. Obtained bio-functionalised surface can be further applied as a protein sensing active microelement.
Presented in this work DLW-based microfabrication technique and the possibilities for further PDA surface post-functionalization empowers advanced applications of this material in single-molecule bioassays, sensors and other complex microdevices.
Polydopamine (PDA) is one of the simplest and most versatile approaches for forming an excellent binding exterior to confer new functionalities to nearly any material surface. Inspired by nature, it mimics the behavior of mussels and can be easily deposited on virtually all types of inorganic and organic substrates, including superhydrophobic surfaces. Moreover, PDA exhibits high potential for surface modification and diversified secondary reactions that makes it extremely interesting for a wide range of application including biomedical field, e.g., drug delivery, adhesives, cell adhesion, biosensing. PDA has undergone significant expansion in its applications and is one of the most attractive areas within the materials field. Nevertheless, PDA integration in microdevices is still constrained by poor spatial and temporal control of excited deposition methods.
Herein, we demonstrate a novel maskless approach for PDA micropatterning based on Direct Laser Writing that overcomes present limitations. The pattern is formed upon exposure of the dopamine solution by light produced by tightly-focused fs NIR laser that scans substrate surface accordingly to the selected pattern design. Neither strong oxidants, metal ions nor adjusting pH to alkaline is required by this technique to perform dopamine polymerization. Our method achieves the PDA micropatterns with the spatial resolution of 0.8 µm, at least an order of magnitude smaller than what is possible with other PDA microplanning techniques. Some examples of PDA patterns are shown in Figure 1. The here introduced PDA deposition technique will uniquely unravel applications of polydopamine and other catecholamine-based mussel-inspired materials in various multifunctional systems and microdevices (e.g., MEMS elements, microfluidics).
The chemical nature of PDA was confirmed by locally recorded vibrational and x-ray photoelectron spectra. Moreover, the morphology and thickness of PDA microstructure can be controlled by the laser power and scanning velocity revealing the possibility of fabricating the structures with gradient. In most of the applied conditions the increase of the laser intensity and decrease of the scanning velocity would lead to the thicker PDA pattern. Different morphologies from smooth and bulky-like to grain like has been obtained.
PDA was produced in the presence of tris buffer, phosphate buffer and DI water only. We also tested the effect of the solution pH applying pH 6.0, 7.0 and 8.5. Furthermore, the effect of antioxidants and purging of the solution with oxygen and nitrogen was investigated. Summarizing, we could see that the structures could be produced in all the given conditions, however their thickness and quality, morphology and roughness would differ. We did not observe negative impact of the antioxidants and nitrogen purging on the performance of PDA build up indicating that the PDA formation mechanism is different to common autooxidation. The current mechanism is based on the interaction of dopamine molecules with the photoinitiator added to solution as active to DLW laser light component.
Apart from the glass substrate, we achieved PDA patterning at surfaces of different nature such as polychlorotrifluoroethylene, polydimethylsiloxane, polyethylene terephthalate, silicon wafers, and fluorinated glass coverslips.
We also performed facile posts-modification of the PDA surface with protein enzymes like trypsin that was confirmed by XPS. Obtained bioactive pattern could be further integrated in the protein sensing devices.
Presented in this work DLW-based microfabrication technique and the possibilities for further PDA surface post-functionalization empowers advanced applications of this material in single-molecule bioassays, sensors and other complex microdevices.
Als bildgebendes und zerstörungsfreies Verfahren eignet sich die Röntgen-Computertomographie (CT) insbesondere bei der Untersuchung von Kunst- und Kulturgütern. Die für Werkstoffprüfung und Materialanalyse konzipierten CT-Anlagen bieten dank hoher Röntgenleistung die Möglichkeit zusätzlich zu Holz, Keramiken und Kunststoffen auch stark schwächende Materialien, wie bspw. Metalle, zu durchdringen. Für eine hohe räumliche Auflösung im unteren Mikrometerbereich (2-200µm) sorgen entsprechend ausgelegte CT-Anlagen. In der Bundesanstalt für Materialforschung und -prüfung (BAM) stehen mehrere solcher CT-Anlagen für unterschiedliche Fragestellungen sowie Probengrößen und - materialien zur Verfügung. Einige Beispiele aus den vergangenen Arbeiten der BAM veranschaulichen das große Potential dieser Untersuchungsmethode.
Da bei einer CT-Messung in der Regel das gesamte Untersuchungsobjekt erfasst und in ein digitales Volumenmodell überführt wird, eröffnet sich für Archäologen und Restoratoren die Möglichkeit Untersuchungen hinsichtlich Materialzusammensetzung, Erhaltungszustand und Herstellungstechnik am virtuellen Objekt vorzunehmen, ohne die Originalsubstanz zu beeinträchtigen. Gegenüber der klassischen Radiografie, bei der nur eine zweidimensionale Abbildung erreicht wird, bietet die CT-Untersuchung die Möglichkeit innenliegende Strukturen dreidimensional zu erfassen. Die notwendige Bestimmung der Objektoberfläche erlaubt zudem die Erstellung eines Oberflächenmodells des untersuchten Gegenstandes. Damit lassen sich unter anderem mechanische Simulationen (Belastung, Durchbiegung, Durchströmung) durchführen. Der erzeugte Datensatz kann somit auch zur Herstellung eines Replikats im 3D-Druckverfahren genutzt werden. Anhand der Untersuchung der Mandoline von Smorsone wird gezeigt, wie eine CT-Messung durchgeführt wird und wie in dem anschließend rekonstruierten 3D-Datensatz mittels Koordinatenmesstechnik Maße (Abstände, Wandstärken, Winkel) exakt ermittelt werden können.
Für die konventionelle Fertigung hat sich das bestehende System der Qualitätsinfrastruktur (QI) bewährt. Die additive Fertigung vergrößert den gestalterischen Spielraum von möglichen Bauteilgeometrien und Prozessfehlern jedoch erheblich. Hier gerät die QI an ihre Grenzen, sodass die Fertigung und Zulassung sicherheits-relevanter Bauteile sehr zeit- und kostenintensive Versuche erfordern. Eine moderne digitale QI erlaubt eine effizientere Qualitätssicherung für additiv gefertigte Bauteile. Dies erfordert eine durchgängig digitale Abbildung des physischen Materialflusses.
When it comes to higher accuracies, new technologies and real applications in additive manufacturing, there is one topic which cannot be avoided: The material response on the chosen processing parameters and its agreement and correspondence with literature data of the wrought material grade counterpart. In industrial Additive Manufacturing (AM) standards in terms of printing parameters, protection gas atmospheres or powder handling instructions are not obligatory. Therefore, the question must be answered whether the AM process is reproducible and reliable over different printing companies. This was the motivation to realize a round robin test between 8 European printing companies and academic partners. The consortium had printed and tested fatigue and tensile testing bars under plant-specific conditions. A commonly used cast aluminum alloy, AlSi10Mg, was chosen as test material for the PBF-LB/M process. Differences of the results between the partners and the scatter itself were discussed in detail.
Lithium-ion batteries (LIBs) are one technology to overcome the challenges of climate and energy crisis. They are widely used in electric vehicles, consumer electronics, or as storage for renewable energy sources. However, despite innovations in batteries' components like cathode and anode materials, separators, and electrolytes, the aging mechanism related to metallic aluminum current collector degradation causes a significant drop in their performance and prevents the durable use of LIBs. Glow-discharge optical emission spectroscopy (GD-OES) is a powerful method for depth-profiling of batteries' electrode materials. This work investigates aging-induced aluminum deposition on commercial lithium cobalt oxide (LCO) batteries' cathodes. The results illustrate the depth-resolved elemental distribution from the cathode surface to the current collector. An accumulation of aluminum is found on the cathode surface by GD-OES, consistent with results from energy-dispersive X-ray spectroscopy (EDX) combined with focused ion beam (FIB) cutting. In comparison to FIB-EDX, GD-OES allows a fast and manageable depth-profiling. Results from different positions on an aged cathode indicate an inhomogeneous aluminum film growth on the surface. The conclusions from these experiments can lead to a better understanding of the degradation of the aluminum current collector, thus leading to higher lifetimes of LIBs.
The unique optoelectronic properties of semiconductor nanocrystals, also termed quantum dots (QDs), have led to many advances in optoelectronic devices, bioimaging, and biosensing. This strong potential in a wide range of applications sparked the interest for a better understanding of the QD formation mechanisms. Recent studies have shown that atomically defined, zero-dimensional magic-size clusters (MSCs) play a crucial role during the nucleation and growth of QDs. Thereby MSCs consist of discrete numbers of ions leading to narrow size distributions and thus narrow absorption peaks, which evolve in discrete steps from one stable size to the next. The formation of MSCs was found in the synthesis of II-VI and III-V QDs but only limited synthesis approaches are available for the synthesis of MSCs in single-ensemble form without coexistence of other-size QDs. These MSCs can further self-assemble into two- and three-dimensional hybrid structures using organic ligands like diamines, leading to enhanced photoluminescence properties and catalytic activities.
In this contribution, we present a synthesis strategy for the preparation of single-sized ZnSe MSCs. With a band gap of 2.7 eV and being an earth-abundant material, ZnSe QDs are interesting for light-emitting devices, blue-green lasers, photocatalysis, and fluorescence probes. In contrast to other studies, our approach is based on a one-pot heat-up synthesis and uses less toxic and dangerous zinc precursors (e.g. zinc stearate). Knowing that thiol-based ligands can alter the formation process of ZnSe QDs, we investigated the influence of 1-dodecanethiol on the ZnSe MSC formation using absorption spectroscopy, TEM, XPS, and XRD. By variation of the thiol ligand concentration and reaction temperature, we were able to synthesize two new ZnSe MSC sizes, the largest so far, by using easy-to-handle precursors.
Nonporous corundum powder was functionalized covalently with protein binders to isolate and enrich specific proteins from complex matrices.The common crosslinker glutaraldehyde was compared with a hyperbranched polyglycerol (PG) of around 10 kDa. The latter was oxidized with periodate to generate aldehyde groups that can covalently react with the amines of the surface and the amino groups from the protein via a reductive amination process. The amount of bound protein was quantified via aromatic amino acid analysis (AAAA). As a proof of concept, IgG was extracted with protein A from crude human plasma. The advantages of corundum include the very low price, extremely high physical and chemical stability, pressure resistance, favorable binding kinetics, convenient handling, and flexible application.
Luminescent lanthanides(III) offer exceptional optical properties that can overcome issues often encountered with other fluorophores (e.g. organic dyes). Their long lifetimes up to milliseconds, low photobleaching and sharp and characteristic emission peaks make the lanthanides extremely valuable for the development of advanced luminescent materials. Previous work on Ru(II) and Ir(III) gold surfaces further highlights the potential of employing the luminescence of metal complexes for the fabrication of sensing platforms and devices.
Here, we incorporate visible and NIR-emitting lanthanide(III) complexes Ln2L3 (Ln = Eu(III), Nd(III), Yb(III)) to gold and plasmonic surfaces, translating the unique optical properties of the lanthanides(III) to practical devices. The Ln2L3 complexes are deposited on the surfaces with different methods, ranging from polymer aided physisorption to the covalent attachment on the gold surface. Furthermore, we exploit the high sensitivity to the coordination environment of lanthanides(III) to design and prepare a sensing platform.