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Item type:Publication, Access status: without files , Engineering of active and passive loss in high-quality-factor vanadium dioxide-based BIC metasurfaces(American Chemical Society (ACS), 2024-08-27); 16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Two-dimensional chiral metasurfaces obtained by geometrically simple meta-atom rotations(American Chemical Society (ACS), 2023-09-19); 7 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Permittivity-asymmetric quasi-bound states in the continuum(American Chemical Society (ACS), 2023-03-22); ; 9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Self-detachment and subsurface densification of dealloyed nanoporoust thin films(American Chemical Society (ACS), 2022-08-24); ; ; ; Experiment shows thin films of dealloyed nanoporous gold (NPG) spontaneously detaching from massive gold base layers. NPG can also densify near its external surface. This is naturally reproduced by kinetic Monte Carlo (KMC) simulation of dealloying and coarsening and so appears generic for nanoscale network materials evolving by surface diffusion. Near the porous layer's external surface and near its interface with the base layer, gradients in the depth-profile of a laterally averaged mean surface curvature provide driving forces for diffusion and cause divergences of the net fluxes of matter, leading to accretion/densification or to erosion/disconnection. As a toy model, the morphology evolution of substrate-supported nanopillars by surface diffusion illustrates and confirms our considerations. Contrary to cylindrical nanowires, the ligaments in nanoporous materials exhibit pre-existing gradients in the mean curvature. The Plateau-Rayleigh long-wavelength stability criterion is then not applicable and the disconnection accelerated.Publicationtype: Journal ArticleScopus© Citations 9 55 159 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Deformation behavior of cross-linked supercrystalline nanocomposites: an in situ SAXS/WAXS study during uniaxial compression(American Chemical Society (ACS), 2021-03-22); ; ; ; With the ever-expanding functional applications of supercrystalline nanocomposites (a relatively new category of materials consisting of organically functionalized nanoparticles arranged into periodic structures), it becomes necessary to ensure their structural stability and understand their deformation and failure mechanisms. Inducing the cross-linking of the functionalizing organic ligands, for instance, leads to a remarkable enhancement of the nanocomposites' mechanical properties. It is however still unknown how the cross-linked organic phase redistributes applied loads, how the supercrystalline lattice accommodates the imposed deformations, and thus in general what phenomena govern the overall material's mechanical response. This work elucidates these aspects for cross-linked supercrystalline nanocomposites through an in situ small- and wide-angle X-ray scattering study combined with uniaxial pressing. Because of this loading condition, it emerges that the cross-linked ligands effectively carry and distribute loads homogeneously throughout the nanocomposites, while the superlattice deforms via rotation, slip, and local defects generation.Publicationtype: Journal ArticleScopus© Citations 12 181 309 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Hydration Friction in Nanoconfinement: From Bulk via Interfacial to Dry FrictionThe viscous properties of nanoscopically confined water are important when hydrated surfaces in close contact are sheared against each other. Numerous experiments have probed the friction between atomically flat hydrated surfaces in the subnanometer separation regime and suggested an increased water viscosity, but the value of the effective viscosity of ultraconfined water, the mechanism of hydration layer friction, and the crossover to the dry friction limit are unclear. We study the shear friction between polar surfaces by extensive nonequilibrium molecular dynamics simulations in the linear-response regime at low shearing velocity, which is the relevant regime for typical biological applications. With decreasing water film thickness we find three consecutive friction regimes: For thick films friction is governed by bulk water viscosity. At separations of about a nanometer the highly viscous interfacial water layers dominate and increase the surface friction, while at the transition to the dry friction limit interfacial slip sets in. Based on our simulation results, we construct a confinement-dependent friction model which accounts for the additive friction contributions from bulklike water, interfacial water layers, and interfacial slip and which is valid for arbitrary water film thickness.Publicationtype: Journal Article11 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Plastic poisson's ratio of nanoporous metals: a macroscopic signature of tension-compression asymmetry at the nanoscale(American Chemical Society (ACS), 2017-09-21); ; ; The suggestion, based on atomistic simulation, of a surface-induced tension-compression asymmetry of the strength and flow stress of small metal bodies so far lacks experimental confirmation. Here, we present the missing experimental evidence. We study the transverse plastic flow of nanoporous gold under uniaxial compression. Performing mechanical tests in electrolyte affords control over the surface state. Specifically, the surface tension, γ, can be varied in situ during plastic flow. We find that decreasing γ leads to an increase of the effective macroscopic plastic Poisson ratio, νP. Finite element simulations of a network with surface tension confirm the notion that νP of nanoporous gold provides a signature for a local tension-compression asymmetry of the nanoscale struts that form the network. We show that γ promotes compression while impeding tensile elongation. Because the transverse strain is partly carried by the elongation of ligaments oriented normal to the load axis, the surface-induced tension-compression asymmetry acts to reduce νP. Our experiment confirms a decisive contribution of the surface tension to small-scale plasticity.Publicationtype: Journal Article143 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Semiordered hierarchical metallic network for fast and large charge-induced strain(American Chemical Society (ACS), 2017-07-27); ; ; ; Nanoporous metallic actuators for artificial muscle applications are distinguished by combining the low operating voltage, which is otherwise reserved for polymer-based actuators with interesting values of strain amplitude, strength, and stiffness that are comparable of those of piezoceramics. We report a nanoporous metal actuator with enhanced strain amplitude and accelerated switching. Our 3D macroscopic metallic muscle has semiordered and hierarchical nanoporous structure, in which μm-sized tubes align perpendicular with the sample surface, while nm-sized ligaments consist of the tube walls. This nanoarchitecture combines channels for fast ion transportation with large surface area for charge storage and strain generation. The result is a record reversible strain amplitude of 1.59% with a strain rate of 8.83 × 10-6 s-1 in the field of metallic based actuators. A passive hydroxide layer is self-grown on the metal surface, which not only contributes a supercapacitive layer, but also stabilizes the nanoporous structure against coarsening, which guarantees sustainable actuation beyond ten-thousand cycles.Publicationtype: Journal Article147 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Magnesium as novel material for active plasmonics in the visible wavelength range(American Chemical Society (ACS), 2015-08-27)4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Active chiral plasmonics(American Chemical Society (ACS), 2015-06-03); Wuttig, MatthiasActive control over the handedness of a chiral metamaterial has the potential to serve as key element for highly integrated polarization engineering approaches, polarization sensitive imaging devices, and stereo display technologies. However, this is hard to achieve as it seemingly involves the reconfiguration of the metamolecule from a left-handed into a right-handed enantiomer and vice versa. This type of mechanical actuation is intricate and usually neither monolithically realizable nor viable for high-speed applications. Here, enabled by the phase change material Ge<inf>3</inf>Sb<inf>2</inf>Te<inf>6</inf> (GST-326), we demonstrate a tunable and switchable mid-infrared plasmonic chiral metamaterial in a proof-of-concept experiment. A large tunability range of the circular dichroism response from = 4.15 to 4.90 m is achieved, and we experimentally demonstrate that the combination of a passive bias-type chiral layer with the active chiral metamaterial allows for switchable chirality, that is, the reversal of the circular dichroism sign, in a fully planar, layered design without the need for geometrical reconfiguration. Because phase change materials can be electrically and optically switched, our designs may open up a path for highly integrated mid-IR polarization engineering devices that can be modulated on ultrafast time scales.Publicationtype: Journal Article7