Tailored nanotopography of photocurable composites for control of cell migration. - In: RSC Advances, ISSN 2046-2069, Bd. 11 (2021), 8, S. 4286-4296
External mechanical stimuli represent elementary signals for living cells to adapt to their adjacent environment. These signals range from bulk material properties down to nanoscopic surface topography and trigger cell behaviour. Here, we present a novel approach to generate tailored surface roughnesses in the nanometer range to tune surface properties by particle size and volume ratio. Time-resolved local mean-squared displacement (LMSD) analysis of amoeboid cell migration reveals that nanorough surfaces alter effectively cell migration velocities and the active cell migration phases. Since the UV curable composite material is easy to fabricate and can be structured via different light based processes, it is possible to generate hierarchical 3D cell scaffolds for tissue engineering or lab-on-a-chip applications with adjustable surface roughness in the nanometre range.
https://doi.org/10.1039/D0RA06530G
Effect of thermoplastic morphology on mechanical properties in laser-assisted joining of polyamide 6 with aluminum. - In: Welding in the world, ISSN 1878-6669, Bd. 65 (2021), 4, S. 699-711
This paper examined the joining zone between semi-crystalline polyamide 6 and aluminum EN AW 6082 in laser-based joining and evaluated the mechanical properties of the joint. The joint tests were carried out in overlap configuration and a characterized in terms of energy per unit length. The mechanical properties were examined to the point of cohesive failure. An increasing energy per unit length resulted in a reduced crosshead displacement in short-term testing and a decreased fatigue strength. Further material testing was carried out locally at various positions within the joining zone. The mechanical properties were correlated with results of a hardness test, thermoplastic morphology, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). By combining the findings with heat-treated samples at elevated temperatures, secondary crystallization was identified and evidenced as a primary effect among the changes in mechanical properties due to the heat treatment of the thermoplastic material.
https://doi.org/10.1007/s40194-020-01048-1
In situ assembly of gold nanoparticles in the presence of poly-DADMAC resulting in hierarchical and highly fractal nanostructures. - In: Applied Sciences, ISSN 2076-3417, Bd. 11 (2021), 3, 1191, S. 1-13
The presence of the polycationic macromolecule poly(diallyldimethylammonium chloride) (poly-DADMAC) has a strong effect on the shape and size of colloidal gold nanoparticles formed by the reduction of tetrachloroauric acid with ascorbic acid in aqueous solution. It slows down nanoparticle growth and supports the formation of nonspherical, partially highly fractal and hierarchical nanoparticle shapes. Four structural levels have been recognized from the near-spherical gold nanoparticles in the lower nanometer range over compact aggregates in the midnanometer range and flower and star-like particles in the submicron range up to larger filamentous aggregates. High-contrast scanning electron microscope (SEM) images show that single gold nanoparticles and clusters of them are connected by bundles of macromolecules in large aggregates. The investigation showed that a large spectrum of different nanoparticle shapes and sizes can be accessed by tuning the poly-DADMAC concentrations and their ratio to other reactants. The nanoassemblies with a very high specific surface area might be of interest for SERS and heterogeneous catalysis.
https://doi.org/10.3390/app11031191
A novel approach to generate a static torque in the range from 1 mN&hahog;m to 1 N&hahog;m :
Ein neuartiger Ansatz zur Erzeugung eines statischen Drehmoments im Bereich von 1 mN&hahog;m bis 1 N&hahog;m. - In: Technisches Messen, ISSN 2196-7113, Bd. 88 (2021), 2, S. 103-113
Drehmomentsensoren mit einem kleinen Messbereich bis zu 1 N&hahog;m sind Teil verschiedener Präzisionsgeräte, wie beispielsweise Roboter oder Werkzeuge für medizinische Operationen und Nanofabrikationsgeräte. Die Drehmomentsensoren benötigen häufig eine Kalibrierung, für die eine Rückführbarkeit nachgewiesen werden muss. Gemäß gesetzlichem Auftrag haben die nationalen metrologischen Institute die Aufgabe, die Drehmomenteinheiten zu realisieren und die geforderte Rückführbarkeit zu ermöglichen. Dieser Artikel zeigt, wie nach einem neuen Prinzip statische Drehmomente im Bereich von 1 mN&hahog;m bis 1 N&hahog;m erzeugt werden können. Ziel der laufenden Arbeiten war die Umsetzung dieser neuen Idee der Drehmomenterzeugung zur Schaffung einer neuen, präziseren Drehmoment-Normalmesseinrichtung. Die Leistungsfähigkeit der neuen Methode wurde mit der Erzeugung von statischen Drehmomenten nach dem Stand der Technik (PTB-Drehmoment-Normalmesseinrichtung) verglichen.
https://doi.org/10.1515/teme-2020-0090
Effects of ocular direct current stimulation on full field electroretinogram. - In: Frontiers in neuroscience, ISSN 1662-453X, Bd. 15 (2021), 606557, S. 1-9
https://doi.org/10.3389/fnins.2021.606557
Negatively charged magnetic nanoparticles pass the blood-placenta barrier under continuous flow conditions in a time-dependent manner. - In: Journal of magnetism and magnetic materials, ISSN 1873-4766, Volume 521 (2021), part 2, 167535
The transfer of substances via the blood-placenta barrier is tightly regulated and critical for the fetus and the expecting mother. In case of necessary medical interventions during pregnancy a comprehensive knowledge about the interaction of the drugs with this barrier is indispensable. Therefore well-engineered test systems are needed and valuable transport systems are helpful. We developed an in vitro microfluidic blood-placenta barrier system consisting of the human trophoblast cell line BeWo and human primary placental pericytes. The integrity and stability of the model was verified by a permeability assay and immunocytochemistry. As potential drug carriers magnetic nanoparticles with various coatings were applied and their ability to pass the barrier was quantified by magnetic particle spectroscopy. We could demonstrate that up to 4% of negatively charged nanoparticles pass the barrier in a time-dependent manner.
https://doi.org/10.1016/j.jmmm.2020.167535
Revisiting the limits of photon momentum based optical power measurement method, employing the case of multi-reflected laser beam. - In: Metrologia, ISSN 1681-7575, Bd. 58 (2021), 1, 015006, insges. 13 S.
In this work, we review the viability and precision of the photon-momentum-based optical power measurement method that employs an amplification effect caused by a multi-reflected laser beam trapped in an optical cavity. Measuring the total momentum transfer of the absorbed and re-emitted photons from a highly reflective surface (reflection of the laser beam from an optical mirror) as a force provides the possibility of measuring the optical power with direct traceability to SI units. Trial measurements were performed at two different metrology laboratories: the laboratory for mass/force at the Technical University of Ilmenau, and the clean room laser radiometry laboratory at PTB, with a portable force measurement setup consisting of two electromagnetic force compensation balances. We compared the results of the optical power measurements performed with the force measurement setup, via the photon-momentum-based method, with those performed using a calibrated reference standard detector traceable to PTB's primary standard for optical power, the cryogenic radiometer. The comparison was carried out for an optical power range between 1 W and 10 W at a wavelength of 532 nm, which corresponds to a force of approximately 2000 nN at the upper limit, yielding approximately 2.3% relative standard uncertainty in the case of 33 reflections. Thus, conflating the high-precision force metrology technique at [my]N to nN levels with the optical setup required to achieve specular multi-reflection configuration of the laser beam, where a macroscopic optical cavity with ultra-high reflective mirrors (>99.995%) can adjustably be suspended from the force sensors, depending on required geometry of reflections, we show that the uncertainty of the optical power measurements upon further increase of the nominally applied optical power, the number of laser beam reflections, or the reflectivity coefficient of the mirrors can be markedly reduced.
https://doi.org/10.1088/1681-7575/abc86e
Layer-by-layer polyelectrolyte assembly for the protection of GaP surfaces from photocorrosion. - In: ACS applied nano materials, ISSN 2574-0970, Bd. 4 (2021), 1, S. 425-431
Polyelectrolyte layer-by-layer assemblies are known as protective coatings for corrosion inhibition. Here, we demonstrate that polyelectrolyte multilayers of poly(ethyleneimine) (PEI) and poly(styrene sulfonate) (PSS)-(PEI/PSS)x-adsorbed at the GaP(100) photocathode surface remarkably mitigate the photocorrosion of GaP without decreasing its photoconversion efficiency. The activity of the polybase-polyacid complex is based on buffering pH changes at the solid-liquid interface. We carried out ab initio molecular dynamics-based simulations of the GaP(100) surface in contact with liquid water and demonstrated that an increase in the proton concentration enhances GaP dissolution. We used the scanning vibrating electrode technique (SVET) to characterize the distribution of photocorrosion activity areas over bare and polyelectrolyte-coated GaP surfaces and we showed that a polyelectrolyte coating impedes the dissolution kinetics. Data obtained using the SVET were compared to photoetched pores on the semiconductor surface. Voltammetric and chronoamperometric measurements were also performed to evaluate photoconversion efficiencies before and after the application of the protective coatings.
https://doi.org/10.1021/acsanm.0c02768
Electrocatalysis of lithium (poly-) sulfides in organic ether-based electrolytes. - In: Journal of the Electrochemical Society, ISSN 1945-7111, Bd. 167 (2021), 16, 166520, insges. 9 S.
https://doi.org/10.1149/1945-7111/abd60c
Method for contact resistance determination of copper during fast temperature changes. - In: Journal of materials science, ISSN 1573-4803, Bd. 56 (2021), 5, S. 3827-3845
https://doi.org/10.1007/s10853-020-05490-w