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End date: 2019 × Start date: 2015 × DDC: 530 × Publisher: Weinheim : Wiley-VCH ×

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Now showing 1 - 10 of 12
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    Surface modification of the laser sintering standard powder polyamide 12 by plasma treatments
    (Weinheim : Wiley-VCH, 2018-6-7) Almansoori, Alaa; Masters, Robert; Abrams, Kerry; Schäfer, Jan; Gerling, Torsten; Majewski, Candice; Rodenburg, Cornelia
    Polyamide 12 (PA12) powder was exposed for up to 3 h to low pressure air plasma treatment (LP-PT) and several minutes by two different atmospheric pressure plasma jets (APPJ) i.e., kINPen (K-APPJ) and Hairline (H-APPJ). The chemical and physical changes resulting from LP-PT were observed by a combination of Scanning Electron Microscopy (SEM), Hot Stage Microscopy (HSM) and Fourier transform infrared spectroscopy (FTIR), which demonstrated significant changes between the plasma treated and untreated PA12 powders. PA12 exposed to LP-PT showed an increase in wettability, was relatively porous, and possessed a higher density, which resulted from the surface functionalization and materials removal during the plasma exposure. However, it showed poor melt behavior under heating conditions typical for Laser Sintering. In contrast, brief PJ treatments demonstrated similar changes in porosity, but crucially, retained the favorable melt characteristics of PA12 powder.
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    The Interaction of Extended Defects as the Origin of Step Bunching in Epitaxial III–V Layers on Vicinal Si(001) Substrates
    (Weinheim : Wiley-VCH, 2019) Niehle, Michael; Rodriguez, Jean-Baptiste; Cerutti, Laurent; Tournié, Eric; Trampert, Achim
    Several nanometer high steps are observed by (scanning) transmission electron microscopy at the surface and interfaces in heteroepitaxially grown III–Sb layers on vicinal Si(001) substrates. Their relations with antiphase boundaries (APBs) and threading dislocations (TDs) are elaborated. An asymmetric number density of TDs on symmetry-equivalent {111} lattice planes is revealed and explained according to the substrate miscut and the lattice misfit in the heteroepitaxial material system. Finally, a step bunching mechanism is proposed based on the interplay of APBs, TDs, and the vicinal surface of the miscut substrate.
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    From patent to product? 50 years of low-pressure plasma sterilization
    (Weinheim : Wiley-VCH, 2018-10-18) Fiebrandt, Marcel; Lackmann, Jan-Wilm; Stapelmann, Katharina
    The 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.
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    Actively Tunable Collective Localized Surface Plasmons by Responsive Hydrogel Membrane
    (Weinheim : Wiley-VCH, 2019) Quilis, Nestor Gisbert; van Dongen, Marcel; Venugopalan, Priyamvada; Kotlarek, Daria; Petri, Christian; Cencerrado, Alberto Moreno; Stanescu, Sorin; Herrera, Jose Luis Toca; Jonas, Ulrich; Möller, Martin; Mourran, Ahmed; Dostalek, Jakub
    Collective (lattice) localized surface plasmons (cLSP) with actively tunable and extremely narrow spectral characteristics are reported. They are supported by periodic arrays of gold nanoparticles attached to a stimuli-responsive hydrogel membrane, which can on demand swell and collapse to reversibly modulate arrays period and surrounding refractive index. In addition, it features a refractive index-symmetrical geometry that promotes the generation of cLSPs and leads to strong suppression of radiative losses, narrowing the spectral width of the resonance, and increasing of the electromagnetic field intensity. Narrowing of the cLSP spectral band down to 13 nm and its reversible shifting by up to 151 nm is observed in the near infrared part of the spectrum by varying temperature and by solvent exchange for systems with a poly(N-isopropylacrylamide)-based hydrogel membrane that is allowed to reversibly swell and collapse in either one or in three dimensions. The reported structures with embedded periodic gold nanoparticle arrays are particularly attractive for biosensing applications as the open hydrogel structure can be efficiently post-modified with functional moieties, such as specific ligands, and since biomolecules can rapidly diffuse through swollen polymer networks. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Hybrid Optical Fibers – An Innovative Platform for In‐Fiber Photonic Devices
    (Weinheim : Wiley-VCH, 2015) Alexander Schmidt, Markus; Argyros, Alexander; Sorin, Fabien
    The field of hybrid optical fibers is one of the most active research areas in current fiber optics and has the vision of integrating sophisticated materials inside fibers, which are not traditionally used in fiber optics. Novel in-fiber devices with unique properties have been developed, opening up new directions for fiber optics in fields of critical interest in modern research, such as biophotonics, environmental science, optoelectronics, metamaterials, remote sensing, medicine, or quantum optics. Here the recent progress in the field of hybrid optical fibers is reviewed from an application perspective, focusing on fiber-integrated devices enabled by including novel materials inside polymer and glass fibers. The topics discussed range from nanowire-based plasmonics and hyperlenses, to integrated semiconductor devices such as optoelectronic detectors, and intense light generation unlocked by highly nonlinear hybrid waveguides.
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    Colloidal Self-Assembly Concepts for Plasmonic Metasurfaces
    (Weinheim : Wiley-VCH, 2019) Mayer, Martin; Schnepf, Max J.; König, Tobias A.F.; Fery, Andreas
    Metallic nanostructures exhibit strong interactions with electromagnetic radiation, known as the localized surface plasmon resonance. In recent years, there is significant interest and growth in the area of coupled metallic nanostructures. In such assemblies, short- and long-range coupling effects can be tailored and emergent properties, e.g., metamaterial effects, can be realized. The term “plasmonic metasurfaces” is used for this novel class of assemblies deposited on planar surfaces. Herein, the focus is on plasmonic metasurfaces formed from colloidal particles. These are formed by self-assembly and can meet the demands of low-cost manufacturing of large-area, flexible, and ultrathin devices. The advances in high optical quality of the colloidal building blocks and methods for controlling their self-assembly on surfaces will lead to novel functional devices for dynamic light modulators, pulse sharpening, subwavelength imaging, sensing, and quantum devices. This progress report focuses on predicting optical properties of single colloidal building blocks and their assemblies, wet-chemical synthesis, and directed self-assembly of colloidal particles. The report concludes with a discussion of the perspectives toward expanding the colloidal plasmonic metasurfaces concept by integrating them with quantum emitters (gain materials) or mechanically responsive structures. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Engineering Micropatterned Dry Adhesives: From Contact Theory to Handling Applications
    (Weinheim : Wiley-VCH, 2018) Hensel, René; Moh, Karsten; Arzt, Eduard
    Reversible 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.
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    Magnetic 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, Helmut
    Inspired 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
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    Real-Time IR Tracking of Single Reflective Micromotors through Scattering Tissues
    (Weinheim : Wiley-VCH, 2019) Aziz, Azaam; Medina-Sánchez, Mariana; Koukourakis, Nektarios; Wang, Jiawei; Kuschmierz, Robert; Radner, Hannes; Czarske, Jürgen W.; Schmidt, Oliver G.
    Medical micromotors have the potential to lead to a paradigm shift in future biomedicine, as they may perform active drug delivery, microsurgery, tissue engineering, or assisted fertilization in a minimally invasive manner. However, the translation to clinical treatment is challenging, as many applications of single or few micromotors require real-time tracking and control at high spatiotemporal resolution in deep tissue. Although optical techniques are a popular choice for this task, absorption and strong light scattering lead to a pronounced decrease of the signal-to-noise ratio with increasing penetration depth. Here, a highly reflective micromotor is introduced which reflects more than tenfold the light intensity of simple gold particles and can be precisely navigated by external magnetic fields. A customized optical IR imaging setup and an image correlation technique are implemented to track single micromotors in real-time and label-free underneath phantom and ex vivo mouse skull tissues. As a potential application, the micromotors speed is recorded when moving through different viscous fluids to determine the viscosity of diverse physiological fluids toward remote cardiovascular disease diagnosis. Moreover, the micromotors are loaded with a model drug to demonstrate their cargo-transport capability. The proposed reflective micromotor is suitable as theranostic tool for sub-skin or organ-on-a-chip applications. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Synthesis of Doped Porous 3D Graphene Structures by Chemical Vapor Deposition and Its Applications
    (Weinheim : Wiley-VCH, 2019) Ullah, Sami; Hasan, Maria; Ta, Huy Q.; Zhao, Liang; Shi, Qitao; Fu, Lei; Choi, Jinho; Yang, Ruizhi; Liu, Zhongfan; Rümmeli, Mark H.
    Graphene doping principally commenced to compensate for its inert nature and create an appropriate bandgap. Doping of 3D graphene has emerged as a topic of interest because of attempts to combine its large available surface area—arising from its interconnected porous architecture—with superior catalytic, structural, chemical, and biocompatible characteristics that can be induced by doping. In light of the latest developments, this review provides an overview of the scalable chemical vapor deposition (CVD)-based growth of doped 3D graphene materials as well as their applications in various contexts, such as in devices used for energy generation and gas storage and biosensors. In particular, single- and multielement doping of 3D graphene by various dopants (such as nitrogen (N), boron (B), sulfur (S) and phosphorous (P)), the doping configurations of the resultant materials, an overview of recent developments in the field of CVD, and the influence of various parameters of CVD on graphene doping and 3D morphologies are focused in this paper. Finally, this report concludes the discussion by mentioning the existing challenges and future opportunities of these developing graphitic materials, intending to inspire the unveiling of more exciting functionalized 3D graphene morphologies and their potential properties, which can hopefully realize many possible applications. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim