Characterization of a magnesium fluoride conversion coating on Mg-2Y-1Mn-1Zn screws for biomedical applications. - In: Materials, ISSN 1996-1944, Bd. 15 (2022), 22, 8245, S. 1-18
MgF2-coated screws made of a Mg-2Y-1Mn-1Zn alloy, called NOVAMag® fixation screws (biotrics bioimplants AG), were tested in vitro for potential applications as biodegradable implants, and showed a controlled corrosion rate compared to non-coated screws. While previous studies regarding coated Mg-alloys have been carried out on flat sample surfaces, the present work focused on functional materials and final biomedical products. The substrates under study had a complex 3D geometry and a nearly cylindrical-shaped shaft. The corrosion rate of the samples was investigated using an electrochemical setup, especially adjusted to evaluate these types of samples, and thus, helped to improve an already patented coating process. A MgF2/MgO coating in the µm-range was characterized for the first time using complementary techniques. The coated screws revealed a smoother surface than the non-coated ones. Although the cross-section analysis revealed some fissures in the coating structure, the electrochemical studies using Hanks’ salt solution demonstrated the effective role of MgF2 in retarding the alloy degradation during the initial stages of corrosion up to 24 h. The values of polarization resistance (Rp) of the coated samples extrapolated from the Nyquist plots were significantly higher than those of the non-coated samples, and impedance increased significantly over time. After 1200 s exposure, the Rp values were 1323 ± 144 Ω.cm2 for the coated samples and 1036 ± 198 Ω.cm2 for the non-coated samples, thus confirming a significant decrease in the degradation rate due to the MgF2 layer. The corrosion rates varied from 0.49 mm/y, at the beginning of the experiment, to 0.26 mm/y after 1200 s, and decreased further to 0.01 mm/y after 24 h. These results demonstrated the effectiveness of the applied MgF2 film in slowing down the corrosion of the bulk material, allowing the magnesium-alloy screws to be competitive as dental and orthopedic solutions for the biodegradable implants market.
https://doi.org/10.3390/ma15228245
Hollow platinum-gold and palladium-gold nanoparticles: synthesis and characterization of composition-structure relationship. - In: Journal of nanoparticle research, ISSN 1572-896X, Bd. 24 (2022), 12, 245, insges. 15 S.
Hollow palladium-gold (PdAu) and platinum-gold (PtAu) alloy nanoparticles (NPs) were synthesized through galvanic replacement reactions. PdAu NPs denoted PdAu-99.99 and PdAu-98 were produced using palladium precursors with different purity degree: Na2PdCl4 ≥ 99.99% and Na2PdCl4 98%, respectively. The effect of the addition time of the gold palladium precursor solution on the size of the generated NPs was evaluated. Two types of particles, with a rough and a smooth surface, were identified in the suspensions of PtAu and PdAu NPs by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM). The atomic percentage of gold, platinum, palladium, and cobalt (atomic %) in the nanoparticles was determined by energy dispersive X-ray spectroscopy (EDX). PtAu NPs (26-42 nm) contain Pt (41 at%), Au (36 at%), and Co (23 at%). Two groups of hollow palladium gold NPs (30-50 nm) with a different residual cobalt content were produced. PdAu-99.99 NPs consisted of Pd (68 at%), Au (26 at%), and Co (6 at%), whereas PdAu-98 NPs were composed of Pd (70 at%), Au (22 at%), and Co (8 at%). The hollow structure of the NPs was confirmed by EDX line scanning. Selected area electron diffraction analysis (SAED) revealed the formation of PtAu and PdAu alloys and it was used in estimating the lattice parameters, too.
https://doi.org/10.1007/s11051-022-05619-9
Clean and hydrogen-adsorbed AlInP(001) surfaces: structures and electronic properties. - In: Physica status solidi, ISSN 1521-3951, Bd. 259 (2022), 11, 2200308, S. 1-6
Total energy and electronic structure calculations based on density functional theory are performed in order to determine the atomic structure and electronic properties of clean and hydrogen-adsorbed Al0.5In0.5P(001) surfaces. It is found that most of the stable surfaces obey the electron-counting rule and are characterized by surface atom dimerization. The dimer-related surface states are predicted to occur in the vicinity of the bulk band edges. For a very narrow range of preparation conditions, ab initio thermodynamics predicts metal atomic wires formed by surface cations. A surface covered with a monolayer of buckled phosphorus dimers, where half of the phosphorus atoms are hydrogen saturated, is found to be stable for metal-organic vapor-phase epitaxy growth conditions. The occurrence of this structure is confirmed by low-energy electron diffraction and X-ray photoelectron spectroscopy data measured on epitaxially grown Al0.52In0.48P(001) epilayers lattice matched to GaAs.
https://doi.org/10.1002/pssb.202200308
Coupling-induced tunable broadband superradiance in 2D metal-dielectric-metal nanocavity arrays. - In: Laser & photonics reviews, ISSN 1863-8899, Bd. 16 (2022), 11, 2200393, S. 1-8
Subradiance/superradiance, cooperative effects causing suppressed/enhanced radiative decay, are of particular interest in plasmonic systems as they play a very important role in modulating dampings and optical properties of resonant systems. However, subradiance/superradiance are generally limited in narrow spectral range with inaccessible tunability. Realizing broadband subradiant and superradiant plasmon modes with flexible tuning is still challenging. Here, a 2D periodic multilayer metal-dielectric-metal (MDM) nanostructure is rationally designed and fabricated to realize a tunable superradiant mode over a broad visible range. Angle-resolved spectroscopy combined with full quantum calculations reveal a sufficient hybridization of delocalized guided plasmons with localized plasmons and a plasmonic cavity mode, leading to an emissive superradiant hybrid mode over a broadband visible range, which can be readily tuned by controlling the spectral three-mode overlap. Greatly shortened polariton lifetimes down to 4 fs are achieved as direct consequence of the Rabi phases and considerable incoherent coupling strengths between interacting subsystems. Such a control of plasmon damping by cooperative mode interactions paves the way toward efficient manipulation of light emission for applications requiring bright, fast-emitting photon sources.
https://doi.org/10.1002/lpor.202200393
Virtuelle Sensorvalidierung für automatisiertes und vernetztes Fahren. - In: Automobiltechnische Zeitschrift, ISSN 2192-8800, Bd. 124 (2022), 11, S. 58-62
https://doi.org/10.1007/s35148-022-1505-0
Design and performance investigation of a novel 3DOF compact MR damper. - In: Smart materials and structures, ISSN 1361-665X, Bd. 31 (2022), 12, 125020, S. 1-14
Magnetorheological fluid (MR) based dampers have been established as an alternative to classical hydraulic dampers with proportional electromagnetic valves under vibration processes which demand adaptive damping forces. Almost all MR-dampers are spatially 1-Degree-of-Freedom (DOF) dampers, having only one axis or direction of damping force generation. In many technical applications there exist movements in more than one spatial DOF, eventually necessitating more than one damper. Because of this, the damping is required not only in one but in more spatial directions, yet adjustable. In this work, a new design of a spatial 3DOF MR damper is proposed to allow damping in three directions within one damping device. The underlying motivation is to spatially integrate three damping directions in one device to potentially reduce installation space compared to three separate 1 DOF dampers. The basic idea of the construction is to use one fluid chamber with several spatially distributed control elements at different positions of the fluid chamber. The control elements are electromagnets, generating the magnetic field in the fluid at different positions so that in total 3 spatial DOFs can be damped individually. Experiments and investigation are made, where the damper's behavior are analyzed not only in one single DOF but also in more than one DOF. It is shown, that the damping concept can generate damping in all three spatial DOFs, both individually or together. Moreover, the damping can be generated to be dominant in one specific direction, meanwhile minimum in the other direction orthogonal to it.
https://doi.org/10.1088/1361-665X/aca12f
Virtual sensor validation for automated and connected driving. - In: ATZ worldwide, ISSN 2192-9076, Bd. 124 (2022), 11, S. 54-57
https://doi.org/10.1007/s38311-022-1405-7
Hybrid additive manufacturing : improved large scale additive manufacturing by means of laser tempering. - In: PhotonicsViews, ISSN 2626-1308, Bd. 19 (2022), 5, S. 47-51
Large-scale additive manufacturing (LSAM) is an additive manufacturing process based on the principles of fused filament fabrication but with significantly higher material deposition rates. The novel hybrid process shown in this paper combines LSAM with a laser beam heat treatment. The structure and mechanical properties of parts are improved due to significantly decreased void sizes. The following article details investigations into the vertical and lateral remelting of strands as well as the utilization of a mirror system, which enables beam guidance according to the machine's printing path.
https://doi.org/10.1002/phvs.202200041
Cochlear implant imaging in the mouse and guinea pig using light-sheet microscopy. - In: Hearing research, ISSN 1878-5891, Bd. 426 (2022), 108639, S. 1-5
Postmortem examination of the cochlea with a cochlear implant in the scala tympani presents several challenges. It is technologically difficult to section a cochlea with an implant due to the presence of its wires and metal components that are adjacent to the membranous and bony tissues of the cochlea. These metal components damage traditional steel blades of a microtome in celloidin, paraffin or frozen embedded tissues. However, plastic embedded implanted cochleas have been successfully sectioned using specialized methods (Irving et al., 2013). An alternative non-destructive method is to optically section a chemically cleared cochlea using light-sheet microscopy, which we will describe in this publication. However, since this method uses a light-sheet to section the cochlea the opaque and reflective metal components of the implant results in some artifacts in the 2D optical sections. The best image quality using light-sheet fluorescent microscopy is when the implant is removed prior to imaging.
https://doi.org/10.1016/j.heares.2022.108639
Induction of embryogenic development in haploid microspore stem cells in droplet-based microfluidics. - In: Lab on a chip, ISSN 1473-0189, Bd. 22 (2022), 22, S. 4292-4305
This work presents the application of droplet-based microfluidics for the cultivation of microspores from Brassica napus using the doubled haploid technology. Under stress conditions (e.g. heat shock) or by chemical induction a certain fraction of the microspores can be reprogrammed and androgenesis can be induced. This process is an important approach for plant breeding because desired plant properties can be anchored in the germline on a genetic level. However, the reprogramming rate of the microspores is generally very low, increasing it by specific stimulation is, therefore, both a necessary and challenging task. In order to accelerate the optimisation and development process, the application of droplet-based microfluidics can be a promising tool. Here, we used a tube-based microfluidic system for the generation and cultivation of microspores inside nL-droplets. Different factors like cell density, tube material and heat shock conditions were investigated to improve the yield of vital plant organoids. Evaluation and analysis of the stimuli response were done on an image base aided by an artificial intelligence cell detection algorithm. Droplet-based microfluidics allowed us to apply large concentration programs in small test volumes and to screen the best conditions for reprogramming cells by the histone deacetylase inhibitor trichostatin A and for enhancing the yield of vital microspores in droplets. An enhanced reprogramming rate was found under the heat shock conditions at 32 ˚C for about 3 to 6 days. In addition, the comparative experiment with MTP showed that droplet cultivation with lower cell density (<10 cells per droplet) or adding media after 3 or 6 days significantly positively affects the microspore growth and embryo rate inside 120 nL droplets. Finally, the developed embryos could be removed from the droplets and further grown into mature plants. Overall, we demonstrated that the droplet-based tube system is suitable for implementation in an automated, miniaturized system to achieve the induction of embryogenic development in haploid microspore stem cells of Brassica napus.
https://doi.org/10.1039/D2LC00788F