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- ItemEngineering Micropatterned Dry Adhesives: From Contact Theory to Handling Applications(Weinheim : Wiley-VCH, 2018) Hensel, René; Moh, Karsten; Arzt, EduardReversible adhesion is the key functionality to grip, place, and release objects nondestructively. Inspired by nature, micropatterned dry adhesives are promising candidates for this purpose and have attracted the attention of research groups worldwide. Their enhanced adhesion compared to nonpatterned surfaces is frequently demonstrated. An important conclusion is that the contact mechanics involved is at least as important as the surface energy and chemistry. In this paper, the roles of the contact geometry and mechanical properties are reviewed. With a focus on applications, the effects of substrate roughness and of temperature variations, and the long-term performance of micropatterned adhesives are discussed. The paper provides a link between the current, detailed understanding of micropatterned adhesives and emerging applications.
- ItemMagnetic Nanoparticle Chains in Gelatin Ferrogels: Bioinspiration from Magnetotactic Bacteria(Weinheim : Wiley-VCH, 2019) Sturm, Sebastian; Siglreitmeier, Maria; Wolf, Daniel; Vogel, Karin; Gratz, Micha; Faivre, Damien; Lubk, Axel; Büchner, Bernd; Sturm, Elena V.; Cölfen, HelmutInspired by chains of ferrimagnetic nanocrystals (NCs) in magnetotactic bacteria (MTB), the synthesis and detailed characterization of ferrimagnetic magnetite NC chain-like assemblies is reported. An easy green synthesis route in a thermoreversible gelatin hydrogel matrix is used. The structure of these magnetite chains prepared with and without gelatin is characterized by means of transmission electron microscopy, including electron tomography (ET). These structures indeed bear resemblance to the magnetite assemblies found in MTB, known for their mechanical flexibility and outstanding magnetic properties and known to crystallographically align their magnetite NCs along the strongest <111> magnetization easy axis. Using electron holography (EH) and angular dependent magnetic measurements, the magnetic interaction between the NCs and the generation of a magnetically anisotropic material can be shown. The electro- and magnetostatic modeling demonstrates that in order to precisely determine the magnetization (by means of EH) inside chain-like NCs assemblies, their exact shape, arrangement and stray-fields have to be considered (ideally obtained using ET). © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemCorrection: Interface-engineered reliable HfO2-based RRAM for synaptic simulation (Journal of Materials Chemistry C (2019) DOI: 10.1039/c9tc04880d)(London [u.a.] : RSC, 2019) Wang, Qiang; Niu, Gang; Roy, Sourav; Wang, Yankun; Zhang, Yijun; Wu, Heping; Zhai, Shijie; Bai, Wei; Shi, Peng; Song, Sannian; Song, Zhitang; Xie, Ya-Hong; Ye, Zuo-Guang; Wenger, Christian; Meng, Xiangjian; Ren, WeiThere was an error in the author list of this published article. The corresponding authors for this paper are Gang Niu (gangniu@xjtu.edu.cn) and Wei Ren (wren@mail.xjtu.edu.cn). The footnote indicating that Qiang Wang and Gang Niu contributed equally to the work was not intended. The corrected author list and notations are shown here. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © The Royal Society of Chemistry 2019.
- ItemOn the anomalous optical conductivity dispersion of electrically conducting polymers: Ultra-wide spectral range ellipsometry combined with a Drude-Lorentz model(London [u.a.] : RSC, 2019) Chen, Shangzhi; Kühne, Philipp; Stanishev, Vallery; Knight, Sean; Brooke, Robert; Petsagkourakis, Ioannis; Crispin, Xavier; Schubert, Mathias; Darakchieva, Vanya; Jonsson, Magnus P.Electrically conducting polymers (ECPs) are becoming increasingly important in areas such as optoelectronics, biomedical devices, and energy systems. Still, their detailed charge transport properties produce an anomalous optical conductivity dispersion that is not yet fully understood in terms of physical model equations for the broad range optical response. Several modifications to the classical Drude model have been proposed to account for a strong non-Drude behavior from terahertz (THz) to infrared (IR) ranges, typically by implementing negative amplitude oscillator functions to the model dielectric function that effectively reduce the conductivity in those ranges. Here we present an alternative description that modifies the Drude model via addition of positive-amplitude Lorentz oscillator functions. We evaluate this so-called Drude-Lorentz (DL) model based on the first ultra-wide spectral range ellipsometry study of ECPs, spanning over four orders of magnitude: from 0.41 meV in the THz range to 5.90 eV in the ultraviolet range, using thin films of poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:Tos) as a model system. The model could accurately fit the experimental data in the whole ultrawide spectral range and provide the complex anisotropic optical conductivity of the material. Examining the resonance frequencies and widths of the Lorentz oscillators reveals that both spectrally narrow vibrational resonances and broader resonances due to localization processes contribute significantly to the deviation from the Drude optical conductivity dispersion. As verified by independent electrical measurements, the DL model accurately determines the electrical properties of the thin film, including DC conductivity, charge density, and (anisotropic) mobility. The ellipsometric method combined with the DL model may thereby become an effective and reliable tool in determining both optical and electrical properties of ECPs, indicating its future potential as a contact-free alternative to traditional electrical characterization. © The Royal Society of Chemistry 2019.
- ItemLayered manganese bismuth tellurides with GeBi4Te7- and GeBi6Te10-type structures: Towards multifunctional materials(London : RSC Publ., 2019) Souchay, Daniel; Nentwig, Markus; Günther, Daniel; Keilholz, Simon; de Boor, Johannes; Zeugner, Alexander; Isaeva, Anna; Ruck, Michael; Wolter, Anja U.B.; Büchnerde, Bernd; Oeckler, OliverThe crystal structures of new layered manganese bismuth tellurides with the compositions Mn0.85(3)Bi4.10(2)Te7 and Mn0.73(4)Bi6.18(2)Te10 were determined by single-crystal X-ray diffraction, including the use of microfocused synchrotron radiation. These analyses reveal that the layered structures deviate from the idealized stoichiometry of the 12P-GeBi4Te7 (space group P3m1) and 51R-GeBi6Te10 (space group R3m) structure types they adopt. Modified compositions Mn1-xBi4+2x/3Te7 (x = 0.15-0.2) and Mn1-xBi6+2x/3Te10 (x = 0.19-0.26) assume cation vacancies and lead to homogenous bulk samples as confirmed by Rietveld refinements. Electron diffraction patterns exhibit no diffuse streaks that would indicate stacking disorder. The alternating quintuple-layer [M2Te3] and septuple-layer [M3Te4] slabs (M = mixed occupied by Bi and Mn) with 1 : 1 sequence (12P stacking) in Mn0.85Bi4.10Te7 and 2 : 1 sequence (51R stacking) in Mn0.81Bi6.13Te10 were also observed in HRTEM images. Temperature-dependent powder diffraction and differential scanning calorimetry show that the compounds are high-temperature phases, which are metastable at ambient temperature. Magnetization measurements are in accordance with a MnII oxidation state and point at predominantly ferromagnetic coupling in both compounds. The thermoelectric figures of merit of n-type conducting Mn0.85Bi4.10Te7 and Mn0.81Bi6.13Te10 reach zT = 0.25 at 375 °C and zT = 0.28 at 325 °C, respectively. Although the compounds are metastable, compact ingots exhibit still up to 80% of the main phases after thermoelectric measurements up to 400 °C. © The Royal Society of Chemistry 2019.
- ItemDevelopment of a model for ultra-precise surface machining of N-BK7® using microwave-driven reactive plasma jet machining(Hoboken, NJ : Wiley Interscience, 2019) Kazemi, Faezeh; Boehm, Georg; Arnold, ThomasIn this paper, extensive studies are conducted as key to overcoming several challenging limitations in applying fluorine-based reactive plasma jet machining (PJM) to surface machining of N-BK7®, particularly regarding the manufacture of freeform optical elements. The chemical composition and lateral distributions of the residual layer are evaluated by X-ray photoelectron spectroscopy and scanning electron microscopy/energy-dispersive X-ray spectroscopy analysis aiming at clarifying the exact chemical kinetics between plasma generated active particles and the N-BK7 surface atoms. Subsequently, a model is developed by performing static etchings to consider the time-varying nonlinearity of the material removal rate and estimate the local etching rate function. Finally, the derived model is extended into the dynamic machining process, and the outcomes are compared with the experimental results.
- ItemFrom patent to product? 50 years of low-pressure plasma sterilization(Weinheim : Wiley-VCH, 2018-10-18) Fiebrandt, Marcel; Lackmann, Jan-Wilm; Stapelmann, KatharinaThe development of new sterilization methods is still a major topic. The need for new techniques arises from the development of new instruments and the usage of different materials. Especially in the case of plastics with their beneficial properties, for example, in the field of implantology, plasma sterilization is seen as a promising alternative to the standard methods. However, 50 years after the first patent and although low-pressure plasmas show excellent inactivation performance (>log 6 reduction), only one commercial system is available on the market for a distinct application. We will give a short review about known plasma sterilization mechanisms, the different plasma sterilization systems in use, analyze possible challenges for an industrial process and comment on possible solutions for a broader acceptance and utilization of low-pressure plasma sterilization.
- ItemWhite paper on plasma for medicine and hygiene: Future in plasma health sciences(Hoboken, NJ : Wiley Interscience, 2019) Bekeschus, Sander; Favia, Pietro; Robert, Eric; von Woedtke, ThomasPlasma Science and Technology offer their valuable contribution to human health since more than 50 years, after decades of experiences in the field of biomaterials; and more than a decade in using plasmas for therapeutic uses in medicine. Current knowledge as well as key challenges and opportunities for the human health have been intensely discussed during the Future in Plasma Science II (FIPS II) workshop in February 2016 in Greifswald, Germany. This contribution summarizes the major outcomes of the meeting and the current literature and consensus with an emphasis on major challenges in the fields of Plasma Science and Technology for improving human health.
- ItemCompetition between proton transfer and intermolecular Coulombic decay in water([London] : Nature Publishing Group UK, 2018) Richter, Clemens; Hollas, Daniel; Saak, Clara-Magdalena; Förstel, Marko; Miteva, Tsveta; Mucke, Melanie; Björneholm, Olle; Sisourat, Nicolas; Slavíček, Petr; Hergenhahn, UweIntermolecular Coulombic decay (ICD) is a ubiquitous relaxation channel of electronically excited states in weakly bound systems, ranging from dimers to liquids. As it is driven by electron correlation, it was assumed that it will dominate over more established energy loss mechanisms, for example fluorescence. Here, we use electron–electron coincidence spectroscopy to determine the efficiency of the ICD process after 2a1 ionization in water clusters. We show that this efficiency is surprisingly low for small water clusters and that it gradually increases to 40–50% for clusters with hundreds of water units. Ab initio molecular dynamics simulations reveal that proton transfer between neighboring water molecules proceeds on the same timescale as ICD and leads to a configuration in which the ICD channel is closed. This conclusion is further supported by experimental results from deuterated water. Combining experiment and theory, we infer an intrinsic ICD lifetime of 12–52 fs for small water clusters.
- ItemCorrection: Electrochemically deposited nanocrystalline InSb thin films and their electrical properties (Journal of Materials Chemistry C (2016) 4 (1345-1350) DOI: 10.1039/C5TC03656A)(London : RSC Publ., 2019) Hnida, K.E.; Bäßler, S.; Mech, J.; Szaciłowski, K.; Socha, R.P.; Gajewska, M.; Nielsch, K.; Przybylski, M.; Sulka, G.D.There was an error in eqn (3) which was reproduced from the literature and used for the interpretation of the results. The calculations (using the equations from an original work from 1987) were done according the correct version of eqn (3) presented below:. (Table Presented). © 2019 The Royal Society of Chemistry.