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DDC: 620 × Type: article × Publisher: Hoboken, NJ : Wiley ×

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Now showing 1 - 10 of 25
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    Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites
    (Hoboken, NJ : Wiley, 2020) Zehner, Jonas; Soldatov, Ivan; Schneider, Sebastian; Heller, René; Khojasteh, Nasrin B.; Schiemenez, Sandra; Fähler, Sebastian; Nielsch, Kornelius; Schäfer, Rudolf; Leistner, Karin
    High energy efficiency of magnetic devices is crucial for applications such as data storage, computation, and actuation. Redox‐based (magneto‐ionic) voltage control of magnetism is a promising room‐temperature pathway to improve energy efficiency. However, for ferromagnetic metals, the magneto‐ionic effects studied so far require ultrathin films with tunable perpendicular magnetic anisotropy or nanoporous structures for appreciable effects. This paper reports a fully reversible, low voltage‐induced collapse of coercivity and remanence by redox reactions in iron oxide/iron films with uniaxial in‐plane anisotropy. In the initial iron oxide/iron films, Néel wall interactions stabilize a blocked state with high coercivity. During the voltage‐triggered reduction of the iron oxide layer, in situ Kerr microscopy reveals inverse changes of coercivity and anisotropy, and a coarsening of the magnetic microstructure. These results confirm a magneto‐ionic deblocking mechanism, which relies on changes of the Néel wall interactions, and of the microstructural domain‐wall‐pinning sites. With this approach, voltage‐controlled 180° magnetization switching with high energy‐efficiency is achieved. It opens up possibilities for developing magnetic devices programmable by ultralow power and for the reversible tuning of defect‐controlled materials in general.
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    Combining Battery‐Type and Pseudocapacitive Charge Storage in Ag/Ti3C2Tx MXene Electrode for Capturing Chloride Ions with High Capacitance and Fast Ion Transport
    (Hoboken, NJ : Wiley, 2020) Liang, Mingxing; Wang, Lei; Presser, Volker; Dai, Xiaohu; Yu, Fei; Ma, Jie
    The recent advances in chloride‐ion capturing electrodes for capacitive deionization (CDI) are limited by the capacity, rate, and stability of desalination. This work introduces Ti3C2Tx/Ag synthesized via a facile oxidation‐reduction method and then uses it as an anode for chloride‐ion capture in CDI. Silver nanoparticles are formed successfully and uniformly distributed with the layered‐structure of Ti3C2Tx. All Ti3C2Tx/Ag samples are hydrophilic, which is beneficial for water desalination. Ti3C2Tx/Ag samples with a low charge transfer resistance exhibit both pseudocapacitive and battery behaviors. Herein, the Ti3C2Tx/Ag electrode with a reaction time of 3 h exhibits excellent desalination performance with a capacity of 135 mg Cl− g−1 at 20 mA g−1 in a 10 × 10−3 m NaCl solution. Furthermore, low energy consumption of 0.42 kWh kg−1 Cl− and a desalination rate of 1.5 mg Cl− g−1 min−1 at 50 mA g−1 is achieved. The Ti3C2Tx/Ag system exhibits fast rate capability, high desalination capacity, low energy consumption, and excellent cyclability, which can be ascribed to the synergistic effect between the battery and pseudocapacitive behaviors of the Ti3C2Tx/Ag hybrid material. This work provides fundamental insight into the coupling of battery and pseudocapacitive behaviors during Cl− capture for electrochemical desalination.
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    Fibrillar elastomeric micropatterns create tunable adhesion even to rough surfaces
    (Hoboken, NJ : Wiley, 2016) Barreau, Viktoriia; Hensel, René; Guimard, Nathalie K.; Ghatak, Animangsu; McMeeking, Robert M.; Arzt, Eduard
    Biologically inspired, fibrillar dry adhesives continue to attract much attention as they are instrumental for emerging applications and technologies. To date, the adhesion of micropatterned gecko-inspired surfaces has predominantly been tested on stiff, smooth substrates. However, all natural and almost all artificial surfaces have roughnesses on one or more different length scales. In the present approach, micropillar-patterned PDMS surfaces with superior adhesion to glass substrates with different roughnesses are designed and analyzed. The results reveal for the first time adhesive and nonadhesive states depending on the micropillar geometry relative to the surface roughness profile. The data obtained further demonstrate that, in the adhesive regime, fibrillar gecko-inspired adhesive structures can be used with advantage on rough surfaces; this finding may open up new applications in the fields of robotics, biomedicine, and space exploration.
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    Virtual Testing of Geometrically Imperfect Additively Manufactured Lattice Structures
    (Hoboken, NJ : Wiley, 2021) Gebhardt, Ulrike; Kästner, Markus; Hufenbach, Julia Kristin; Kühn, Uta; Berner, Matthias; Holtzhausen, Stefan
    Additively manufactured lattice structures increase the lightweight potential of components for technical applications. When modelling the mechanical behaviour of those lattice structures, imperfections within the structures need to be considered. In this contribution we investigate the effect of process induced pores of varying size and location inside the lattice structure during pressure tests using a 2D minimal model in two configurations. It shows that the location of pores with respect to the configuration of the model has a strong influence on whether the imperfection decreases the mechanical performance.
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    Contact Aging Enhances Adhesion of Micropatterned Silicone Adhesives to Glass Substrates
    (Hoboken, NJ : Wiley, 2020) Thiemecke, Jonathan; Hensel, René
    The transfer of biological concepts into synthetic micropatterned adhesives has recently enabled a new generation of switchable, reversible handling devices. Over the last two decades, many design principles have been explored that helped to understand the underlying mechanics and to optimize such adhesives for certain applications. An aspect that has been overlooked so far is the influence of longer hold times on the adhesive contacts. Exemplarily, the pull‐off stress and work of separation of a micropatterned adhesive specimen are enhanced by factors 3 and 6, respectively, after 1000 min in contact with a glass substrate. In addition to such global measures, the increase of adhesion of all individual micropillars is analyzed. It is found that contact aging varied across the microarray, as it drastically depends on local conditions. Despite great differences on the micropillar scale, the adhesion of entire specimens increased with very similar power laws, as this is determined by the mean contact ageing of the individual structures. Overall, contact aging must be critically evaluated before using micropatterned adhesives, especially for long‐term fixations and material combinations that are chemically attractive to each other.
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    Maximizing transfection efficiency of vertically aligned silicon nanowire arrays
    (Hoboken, NJ : Wiley, 2015) Elnathan, Roey; Delalat, Bahman; Brodoceanu, Daniel; Alhoud, Hashim; Harding, Frances J.; Buehler, Katrin; Nelson, Adrienne; Isa, Lucio; Kraus, Tobias; Voelcker, Nicolas H.
    Vertically aligned silicon nanowire (VA‐SiNW) arrays are emerging as a powerful new tool for gene delivery by means of mechanical transfection. In order to utilize this tool efficiently, uncertainties around the required design parameters need to be removed. Here, a combination of nanosphere lithography and templated metal‐assisted wet chemical etching is used to fabricate VA‐SiNW arrays with a range of diameters, heights, and densities. This fabrication strategy allows identification of critical parameters of surface topography and consequently the design of SiNW arrays that deliver plasmid with high transfection efficiency into a diverse range of human cells whilst maintaining high cell viability. These results illuminate the cell‐materials interactions that mediate VA‐SiNW transfection and have the potential to transform gene therapy and underpin future treatment modalities.
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    Stimuli‐responsive microjets with reconfigurable shape
    (Hoboken, NJ : Wiley, 2014) Magdanz, Veronika; Stoychev, Georgi; Ionov, Leonid; Sanchez, Samuel; Schmidt, Oliver.G.
    Flexible thermoresponsive polymeric microjets are formed by the self‐folding of polymeric layers containing a thin Pt film used as catalyst for self‐propulsion in solutions containing hydrogen peroxide. The flexible microjets can reversibly fold and unfold in an accurate manner by applying changes in temperature to the solution in which they are immersed. This effect allows microjets to rapidly start and stop multiple times by controlling the radius of curvature of the microjet. This work opens many possibilities in the field of artificial nanodevices, for fundamental studies on self‐propulsion at the microscale, and also for biorelated applications.
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    Mononuclear clusterfullerene single‐molecule magnet containing strained fused‐pentagons stabilized by a nearly linear metal cyanide cluster
    (Hoboken, NJ : Wiley, 2017) Liu, Fupin; Wang, Song; Gao, Cong-Li; Deng, Qingming; Zhu, Xianjun; Kostanyan, Aram; Westerstrçm, Rasmus; Jin, Fei; Xie, Su‐Yuan; Popov, Alexey A.; Greber, Thomas; Yang, Shangfeng
    Fused‐pentagons results in an increase of local steric strain according to the isolated pentagon rule (IPR), and for all reported non‐IPR clusterfullerenes multiple (two or three) metals are required to stabilize the strained fused‐pentagons, making it difficult to access the single‐atom properties. Herein, we report the syntheses and isolations of novel non‐IPR mononuclear clusterfullerenes MNC@C76 (M=Tb, Y), in which one pair of strained fused‐pentagon is stabilized by a mononuclear cluster. The molecular structures of MNC@C76 (M=Tb, Y) were determined unambiguously by single‐crystal X‐ray diffraction, featuring a non‐IPR C2v(19138)‐C76 cage entrapping a nearly linear MNC cluster, which is remarkably different from the triangular MNC cluster within the reported analogous clusterfullerenes based on IPR‐obeying C82 cages. The TbNC@C76 molecule is found to be a field‐induced single‐molecule magnet (SMM).
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    Magnetic suspension array technology: Controlled synthesis and screening in microfluidic networks
    (Hoboken, NJ : Wiley, 2016) Lin, Gungun; Karnaushenko, Dmitriy D.; Cañón Bermúdez, Gilbert Santiago; Schmidt, Oliver G.; Makarov, Denys
    Information tagging and processing are vital in information‐intensive applications, e.g., telecommunication and high‐throughput drug screening. Magnetic suspension array technology may offer intrinsic advantages to screening applications by enabling high distinguishability, the ease of code generation, and the feasibility of fast code readout, though the practical applicability of magnetic suspension array technology remains hampered by the lack of quality administration of encoded microcarriers. Here, a logic‐controlled microfluidic system enabling controlled synthesis of magnetic suspension arrays in multiphase flow networks is realized. The smart and compact system offers a practical solution for the quality administration and screening of encoded magnetic microcarriers and addresses the universal need of process control for synthesis in microfluidic networks, i.e., on‐demand creation of droplet templates for high information capacity. The demonstration of magnetic suspension array technology enabled by magnetic in‐flow cytometry opens the avenue toward point‐of‐care multiplexed bead‐based assays, clinical diagnostics, and drug discovery.
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    Selective Out‐of‐Plane Optical Coupling between Vertical and Planar Microrings in a 3D Configuration
    (Hoboken, NJ : Wiley, 2020) Valligatla, Sreeramulu; Wang, Jiawei; Madani, Abbas; Naz, Ehsan Saei Ghareh; Hao, Qi; Saggau, Christian Niclaas; Yin, Yin; Ma, Libo; Schmidt, Oliver G.
    3D photonic integrated circuits are expected to play a key role in future optoelectronics with efficient signal transfer between photonic layers. Here, the optical coupling of tubular microcavities, supporting resonances in a vertical plane, with planar microrings, accommodating in‐plane resonances, is explored. In such a 3D coupled composite system with largely mismatched cavity sizes, periodic mode splitting and resonant mode shifts are observed due to mode‐selective interactions. The axial direction of the microtube cavity provides additional design freedom for selective mode coupling, which is achieved by carefully adjusting the axial displacement between the microtube and the microring. The spectral anticrossing behavior is caused by strong coupling in this composite optical system and is excellently reproduced by numerical modeling. Interfacing tubular microcavities with planar microrings is a promising approach toward interlayer light transfer with added optical functionality in 3D photonic systems.