Contamination-assisted rather than metal catalyst-free bottom-up growth of silicon nanowires. - In: Advanced materials interfaces, ISSN 2196-7350, Bd. 8 (2021), 22, 2101121, insges. 9 S.
Well-established metal-catalyzed vapor-liquid-solid (VLS) growth represents still undoubtedly the key technology for bottom-up synthesis of single-crystalline silicon nanowires (SiNWs). Although various SiNW applications are demonstrated, electrical and optical properties are exposed to the inherent risk of electronic deep trap state formation by metal impurities. Therefore, metal catalyst-free growth strategies are intriguing. The oxid-assisted SiNW synthesis is explored and it is shown that contamination control is absolutely crucial. Slightest metal impurities, such as iron, are sufficient to trigger SiNW growth, calling into question true metal catalyst-free SiNW synthesis. Therefore, the term contamination-assisted is rather introduced and it is shown that contamination-assisted SiNW growth is determined by the chemical surface treatment (e.g., with KOH solution), but also by the crystal orientation of a silicon substrate. SiNWs are grown in this regards in a reproducible manner, but so far with a distinct tapering, using a conventional gas-phase reactor system at temperatures of about 680 ˚C and monosilane (SiH4) as the precursor gas. The synthesized SiNWs show convincing electrical properties compared to Au-catalyzed SiNWs. Nevertheless, contamination-assisted growth of SiNWs appears to be an important step toward bottom-up synthesis of high-quality SiNWs with a lower risk of metal poisoning, such as those needed for CMOS and other technologies.
https://doi.org/10.1002/admi.202101121
Naučnye issledovanija na osnove modelirovanija s celьju raspoznavanija sily putem monitoringa a deformacionnogo sostojanija gibkogo mechanizma :
Model-based investigations of force detection by monitoring the deformation state of a compliant mechanism. - In: Problems of mechanics, ISSN 1512-0740, (2021), No. 3(84), Seite 51-62
A strong, long-lasting pressure on the human skin whose effect is increased by shear forces can lead to the development of a pressure ulcer (decubitus). In order to minimize the risk of pressure ulcers developing, critical forces acting between the body and a sitting or lying surface should be detected and eliminated in time. One possibility for detecting critical forces is the actuation of tactile switches. In this article, miniature tactile switches are integrated into a compliant mechanism using the example of a MATF1 mattress spring made by Hartmann Kunststofftechnik GmbH & Co. KG. For this purpose, the deformation behavior of the spring is analyzed by means of non-linear analytical and finite elements method (FEM) calculations and the required tactile switches parameters as well as suitable locations for their placement are determined. A functional model is then built and examined.
Textured and hierarchically constructed polymer micro- and nanoparticles. - In: Applied Sciences, ISSN 2076-3417, Bd. 11 (2021), 21, 10421, S. 1-17
Microfluidic techniques allow for the tailored construction of specific microparticles, which are becoming increasingly interesting and relevant. Here, using a microfluidic hole-plate-device and thermal-initiated free radical polymerization, submicrometer polymer particles with a highly textured surface were synthesized. Two types of monomers were applied: (1) methylmethacrylate (MMA) combined with crosslinkers and (2) divinylbenzene (DVB). Surface texture and morphology can be influenced by a series of parameters such as the monomer-crosslinker-solvent composition, surfactants, and additives. Generally, the most structured surfaces with the simultaneously most uniform particles were obtained in the DVB-toluene-nonionic-tensides system. In a second approach, poly-MMA (PMMA) particles were used to build aggregates with bigger polymer particles. For this purpose, tripropyleneglycolediacrylate (TPGDA) particles were synthesized in a microfluidic co-flow arrangement and polymerized by light- irradiation. Then, PMMA particles were assembled at their surface. In a third step, these composites were dispersed in an aqueous acrylamide-methylenebisacrylamide solution, which again was run through a co-flow-device and photopolymerized. As such, entities consisting of particles of three different size ranges - typically 0.7/30/600 [my]m - were obtained. The particles synthesized by both approaches are potentially suitable for loading with or incorporation of analytic probes or catalysts such as dyes or metals.
https://doi.org/10.3390/app112110421
Updated insights into 3D architecture electrodes for micropower sources. - In: Advanced materials, ISSN 1521-4095, Bd. 33 (2021), 45, 2103304, insges. 17 S.
Microbatteries (MBs) and microsupercapacitors (MSCs) are primary on-chip micropower sources that drive autonomous and stand-alone microelectronic devices for implementation of the Internet of Things (IoT). However, the performance of conventional MBs and MSCs is restricted by their 2D thin-film electrode design, and these devices struggle to satisfy the increasing IoT energy demands for high energy density, high power density, and long lifespan. The energy densities of MBs and MSCs can be improved significantly through adoption of a 2D thick-film electrode design; however, their power densities and lifespans deteriorate with increased electrode thickness. In contrast, 3D architecture electrodes offer remarkable opportunities to simultaneously improve MB and MSC energy density, power density, and lifespan. To date, various 3D architecture electrodes have been designed, fabricated, and investigated for MBs and MSCs. This review provides an update on the principal superiorities of 3D architecture electrodes over 2D thick-film electrodes in the context of improved MB and MSC energy density, power density, and lifespan. In addition, the most recent and representative progress in 3D architecture electrode development for MBs and MSCs is highlighted. Finally, present challenges are discussed and key perspectives for future research in this field are outlined.
https://doi.org/10.1002/adma.202103304
Modulation of human intraocular pressure using a pneumatic system. - In: Translational Vision Science & Technology, ISSN 2164-2591, Bd. 10 (2021), 14, 4, S. 1-9
https://doi.org/10.1167/tvst.10.14.4
Bio-inspired self-assembly of large area 3D AgSiO2 plasmonic nanostructures with tunable broadband light harvesting. - In: Applied materials today, ISSN 2352-9407, Bd. 25 (2021), 101238
Tremendous efforts have been made to fabricate large-scale plasmonic nanostructures, which show wide applications in surface plasmon resonance (SPR) sensing, catalytic conversion, photothermal conversion, optoelectronics, photothermal therapy. However, unable to fabricate over 5 cm^2 plasmonic nanostructures with good controllability hinders their further applications. Here, super large-scale (153 cm^2) 3D AgSiO2 hybrid plasmonic nanostructures with adjustable and ultra-broadband light absorption are fabricated by a simple and controllable two-step approach. The metastable atomic layer deposition (MS-ALD) is combined with physical vapor deposition (PVD) to generate these structures in a self-assembly manner. The structures look like coral tentacles. These excellent properties are attributed to multiple forward scatterings and extinction effects produced by Ag@SiO2 nanostructures. Using 3D Ag@SiO2 plasmonic nanostructures as light absorber for bottom-heating-based evaporation, the water evaporation rate remarkably improves seven times under 1 Sun than that in dark condition. Our results pave the avenue for developing super large-scale Ag-based plasmonic nanostructure with potential applications in solar energy conversion.
https://doi.org/10.1016/j.apmt.2021.101238
Recent development of electrocatalytic CO2 reduction application to energy conversion. - In: Small, ISSN 1613-6829, Bd. 17 (2021), 44, 2100323, insges. 29 S.
Im Titel ist "2" tiefgestellt
Carbon dioxide (CO2) emission has caused greenhouse gas pollution worldwide. Hence, strengthening CO2 recycling is necessary. CO2 electroreduction reaction (CRR) is recognized as a promising approach to utilize waste CO2. Electrocatalysts in the CRR process play a critical role in determining the selectivity and activity of CRR. Different types of electrocatalysts are introduced in this review: noble metals and their derived compounds, transition metals and their derived compounds, organic polymer, and carbon-based materials, as well as their major products, Faradaic efficiency, current density, and onset potential. Furthermore, this paper overviews the recent progress of the following two major applications of CRR according to the different energy conversion methods: electricity generation and formation of valuable carbonaceous products. Considering electricity generation devices, the electrochemical properties of metal-CO2 batteries, including Li-CO2, Na-CO2, Al-CO2, and Zn-CO2 batteries, are mainly summarized. Finally, different pathways of CO2 electroreduction to carbon-based fuels is presented, and their reaction mechanisms are illustrated. This review provides a clear and innovative insight into the entire reaction process of CRR, guiding the new electrocatalysts design, state-of-the-art analysis technique application, and reaction system innovation.
https://doi.org/10.1002/smll.202100323
Mean-field approximations of networks of spiking neurons with short-term synaptic plasticity. - In: Physical review, ISSN 2470-0053, Bd. 104 (2021), 4, 044310, insges. 15 S.
Low-dimensional descriptions of spiking neural network dynamics are an effective tool for bridging different scales of organization of brain structure and function. Recent advances in deriving mean-field descriptions for networks of coupled oscillators have sparked the development of a new generation of neural mass models. Of notable interest are mean-field descriptions of all-to-all coupled quadratic integrate-and-fire (QIF) neurons, which have already seen numerous extensions and applications. These extensions include different forms of short-term adaptation considered to play an important role in generating and sustaining dynamic regimes of interest in the brain. It is an open question, however, whether the incorporation of presynaptic forms of synaptic plasticity driven by single neuron activity would still permit the derivation of mean-field equations using the same method. Here we discuss this problem using an established model of short-term synaptic plasticity at the single neuron level, for which we present two different approaches for the derivation of the mean-field equations. We compare these models with a recently proposed mean-field approximation that assumes stochastic spike timings. In general, the latter fails to accurately reproduce the macroscopic activity in networks of deterministic QIF neurons with distributed parameters. We show that the mean-field models we propose provide a more accurate description of the network dynamics, although they are mathematically more involved. Using bifurcation analysis, we find that QIF networks with presynaptic short-term plasticity can express regimes of periodic bursting activity as well as bistable regimes. Together, we provide novel insight into the macroscopic effects of short-term synaptic plasticity in spiking neural networks, as well as two different mean-field descriptions for future investigations of such networks.
https://doi.org/10.1103/PhysRevE.104.044310
Molecular characterization of hematopoietic stem cells after in vitro amplification on biomimetic 3D PDMS cell culture scaffolds. - In: Scientific reports, ISSN 2045-2322, Bd. 11 (2021), 21163, S. 1-14
Hematopoietic stem cell (HSC) transplantation is successfully applied since the late 1950s. However, its efficacy can be impaired by insufficient numbers of donor HSCs. A promising strategy to overcome this hurdle is the use of an advanced ex vivo culture system that supports the proliferation and, at the same time, maintains the pluripotency of HSCs. Therefore, we have developed artificial 3D bone marrow-like scaffolds made of polydimethylsiloxane (PDMS) that model the natural HSC niche in vitro. These 3D PDMS scaffolds in combination with an optimized HSC culture medium allow the amplification of high numbers of undifferentiated HSCs. After 14 days in vitro cell culture, we performed transcriptome and proteome analysis. Ingenuity pathway analysis indicated that the 3D PDMS cell culture scaffolds altered PI3K/AKT/mTOR pathways and activated SREBP, HIF1α and FOXO signaling, leading to metabolic adaptations, as judged by ELISA, Western blot and metabolic flux analysis. These molecular signaling pathways can promote the expansion of HSCs and are involved in the maintenance of their pluripotency. Thus, we have shown that the 3D PDMS scaffolds activate key molecular signaling pathways to amplify the numbers of undifferentiated HSCs ex vivo effectively.
https://doi.org/10.1038/s41598-021-00619-6
Nanocomplex of Berberine with C60 fullerene is a potent suppressor of Lewis lung carcinoma cells invasion in vitro and metastatic activity in vivo. - In: Materials, ISSN 1996-1944, Bd. 14 (2021), 20, 6114, insges. 15 S.
Im Titel ist "60" tiefgestellt
Effective targeting of metastasis is considered the main problem in cancer therapy. The development of herbal alkaloid Berberine (Ber)-based anticancer drugs is limited due to Ber’ low effective concentration, poor membrane permeability, and short plasma half-life. To overcome these limitations, we used Ber noncovalently bound to C60 fullerene (C60). The complexation between C60 and Ber molecules was evidenced with computer simulation. The aim of the present study was to estimate the effect of the free Ber and C60-Ber nanocomplex in a low Ber equivalent concentration on Lewis lung carcinoma cells (LLC) invasion potential, expression of epithelial-to-mesenchymal transition (EMT) markers in vitro, and the ability of cancer cells to form distant lung metastases in vivo in a mice model of LLC. It was shown that in contrast to free Ber its nanocomplex with C60 demonstrated significantly higher efficiency to suppress invasion potential, to downregulate the level of EMT-inducing transcription factors SNAI1, ZEB1, and TWIST1, to unblock expression of epithelial marker E-cadherin, and to repress cancer stem cells-like markers. More importantly, a relatively low dose of C60-Ber nanocomplex was able to suppress lung metastasis in vivo. These findings indicated that сomplexation of natural alkaloid Ber with C60 can be used as an additional therapeutic strategy against aggressive lung cancer.
https://doi.org/10.3390/ma14206114