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Ullrich Steiner - One of the best experts on this subject based on the ideXlab platform.

  • optical imaging of large Gyroid grains in block copolymer templates by confined crystallization
    Macromolecules, 2017
    Co-Authors: Raphael Dehmel, B. D. Wilts, James A. Dolan, Ulrich Wiesner, Timothy D. Wilkinson, Jeremy J. Baumberg, Ullrich Steiner, Ilja Gunkel
    Abstract:

    Block copolymer (BCP) self-assembly is a promising route to manufacture functional nanomaterials for applications from nanolithography to optical metamaterials. Self-assembled cubic morphologies cannot, however, be conveniently optically characterized in the lab due to their structural isotropy. Here, the aligned crystallization behavior of a semicrystalline-amorphous polyisoprene-b-polystyrene-b-poly(ethylene oxide) (ISO) triblock terpolymer was utilized to visualize the grain structure of the cubic microphase-separated morphology. Upon quenching from a solvent swollen state, ISO first self-assembles into an alternating Gyroid morphology, in the confinement of which the PEO crystallizes preferentially along the least tortuous pathways of the single Gyroid morphology with grain sizes of hundreds of micrometers. Strikingly, the resulting anisotropic alignment of PEO crystallites gives rise to a unique optical birefringence of the alternating Gyroid domains, which allows imaging of the self-assembled grain ...

  • Gyroid Optical Metamaterials: Calculating the Effective Permittivity of Multidomain Samples.
    ACS photonics, 2016
    Co-Authors: James A. Dolan, Ortwin Hess, Matthias Saba, Raphael Dehmel, Ilja Gunkel, Ulrich Wiesner, Timothy D. Wilkinson, Jeremy J. Baumberg, Ullrich Steiner
    Abstract:

    Gold Gyroid optical metamaterials are known to possess a reduced plasma frequency and linear dichroism imparted by their intricate subwavelength single Gyroid morphology. The anisotropic optical properties are, however, only evident when a large individual Gyroid domain is investigated. Multidomain Gyroid metamaterials, fabricated using a polyisoprene-b-polystyrene-b-poly(ethylene oxide) triblock terpolymer and consisting of multiple small Gyroid domains with random orientation and handedness, instead exhibit isotropic optical properties. Comparing three effective medium models, we here show that the specular reflectance spectra of such multidomain Gyroid optical metamaterials can be accurately modeled over a broad range of incident angles by a Bruggeman effective medium consisting of a random wire array. This model accurately reproduces previously published results tracking the variation in normal incidence reflectance spectra of gold Gyroid optical metamaterials as a function of host refractive index an...

  • Visualization of energy: light dose indicator based on electrochromic Gyroid nano-materials.
    Nanotechnology, 2015
    Co-Authors: Di Wei, Maik R. J. Scherer, Michael Astley, Ullrich Steiner
    Abstract:

    The typical applications of electrochromic devices do not make use of the charge-dependent, gradual optical response due to their slow voltage-sensitive coloration. However, in this paper we present a design for a reusable, self-powered light dose indicator consisting of a solar cell and a Gyroid-structured nickel oxide (NiO) electrochromic display that measures the cumulative charge per se, making use of the efficient voltage-sensitive coloration of Gyroid materials. To circumvent the stability issues associated with the standard aqueous electrolyte that is typically accompanied by water splitting and gas evolution, we investigate a novel nano-Gyroid NiO electrochromic device based on organic solvents of 1,1,1,3,3,3-hexafluoropropan-2-ol, and room temperature ionic liquid (RTIL) triethylsulfonium bis(trifluoromethylsulfonyl) imide ([SET3][TFSI]) containing lithium bis(trifluoromethylsulfonyl) imide. We show that an effective light dose indicator can be enabled by nano-Gyroid NiO with RTIL; this proves to be a reliable device since it does not involve solvent degradation or gas generation.

  • Optical Properties of Gyroid Structured Materials: From Photonic Crystals to Metamaterials
    Advanced Optical Materials, 2014
    Co-Authors: James A. Dolan, B. D. Wilts, Jeremy J. Baumberg, Ullrich Steiner, Silvia Vignolini, Timothy D. Wilkinson
    Abstract:

    The Gyroid is a continuous and triply periodic cubic morphology which possesses a constant mean curvature surface across a range of volumetric fill fractions. Found in a variety of natural and synthetic systems which form through self-assembly, from butterfly wing scales to block copolymers, the Gyroid also exhibits an inherent chirality not observed in any other similar morphologies. These unique geometrical properties impart to Gyroid structured materials a host of interesting optical properties. Depending on the length scale on which the constituent materials are organised, these properties arise from starkly different physical mechanisms (such as a complete photonic bandgap for photonic crystals and a greatly depressed plasma frequency for optical metamaterials). This article reviews the theoretical predictions and experimental observations of the optical properties of two fundamental classes of Gyroid structured materials: photonic crystals (wavelength scale) and metamaterials (sub-wavelength scale).

  • control of Gyroid forming block copolymer templates effects of an electric field and surface topography
    Soft Matter, 2010
    Co-Authors: Ullrich Steiner, Marc A. Hillmyer, Edward J W Crossland, Sabine Ludwigs
    Abstract:

    The control over 10 nm scale porosity derived from self-assembly of copolymers is an extremely promising method for the synthesis of organic–inorganic hybrid materials applied, for example, in solar cells. Here, we report the thin film behaviour of a poly(4-fluorostyrene)-b-poly(D,L-lactide) PFS-b-PLA block copolymer which adopts the bicontinuous Gyroid phase in the bulk and may be used to form a porous template suitable for patterning functional materials by selective degradation of the minority PLA domains. The response of the copolymer morphology to DC electric fields is probed at temperatures where the bulk copolymer adopts either the Gyroid or the cylindrical phase. At 150 °C electric field alignment results in vertical arrays of cylinders, lamellae, and perforated lamellae while at 180 °C the Gyroid phase coexists with a standing perforated lamellar phase. We show that both polymer–substrate interactions and substrate topography are critical factors determining substrate reconstruction of the Gyroid phase. Spontaneous cross-film percolation of the minority network phase on a given substrate, a prerequisite for electrochemical replication, is dependent on surface topology at the scale of the Gyroid unit cell. Importantly, under suitable processing conditions all these complex copolymer morphologies can be electrochemically replicated to produce highly ordered freestanding nanostructured arrays over large areas.

Ken Gall - One of the best experts on this subject based on the ideXlab platform.

  • Fatigue behavior of As-built selective laser melted titanium scaffolds with sheet-based Gyroid microarchitecture for bone tissue engineering
    Acta Biomaterialia, 2019
    Co-Authors: Cambre N. Kelly, Jaedyn Francovich, Stefan Julmi, Robert E. Guldberg, David Lee Safranski, Hans Jürgen Maier, Ken Gall
    Abstract:

    Abstract Selective laser melting (SLM) has enabled the production of porous titanium structures with biological and mechanical properties that mimic bone for orthopedic applications. These porous structures have a reduced effective stiffness which leads to improved mechanotransduction between the implant and bone. Triply periodic minimal surfaces (TMPS), specifically the sheet-based Gyroid structures, have improved compressive fatigue resistance due lack of stress concentrations. Sheet-based Gyroid microarchitectures also have high surface area, permeability, and zero mean curvature. This study examines the effects of the Gyroid microarchitectural design in parallel with SLM parameters on structure and function of as-built titanium alloy (Ti6Al4V ELI) scaffolds. Scaffold design was varied by varying unit cell size and wall thickness to produce scaffolds with porosity within the range of trabecular bone (50–90%). Manufacturer’s default and refined laser parameters were used to examine the effect of input energy density on mechanical properties. Scaffolds exhibited a stretching-dominated deformation behavior under both compressive and tensile loading, and porosity dependent stiffness and strength. Internal void defects were observed within the walls of the Gyroids structure, serving as sites for crack initiation leading to failure. Refinement of laser parameters resulted in increased compressive and tensile fatigue behavior, particularly for thicker walled Gyroid microarchitectures, while thinner walls showed no significant change. The observed properties of as-built Gyroid sheet microarchitectures indicates that these structures have potential for use in bone engineering applications. Furthermore, these results highlight the importance of parallel design and processing optimization for complex sheet-based porous structures produced via SLM. Statement of Significance Selective laser melting (SLM) is an additive manufacturing technology which produces complex porous scaffolds for orthopedic applications. Titanium alloy scaffolds with novel sheet-based Gyroid microarchitectures were produced via SLM and evaluated for mechanical performance including fatigue behavior. Gyroid structures are function based topologies have been hypothesized to be promising for tissue engineering scaffolds due to the high surface area to volume ratio, zero mean curvature, and high permeability. This paper presents the effects of scaffold design and processing parameters in parallel, a novel study in the field on bone tissue scaffolds produced via additive manufacturing. Additionally, the comparison of compressive and tensile behavior of scaffolds presented is important in characterizing behavior and failure mechanisms of porous metals which undergo complex loading in orthopedic applications.

Sharon C. Glotzer - One of the best experts on this subject based on the ideXlab platform.

  • Stability of the double Gyroid phase to nanoparticle polydispersity in polymer-tethered nanosphere systems
    Soft Matter, 2010
    Co-Authors: Carolyn L. Phillips, Christopher R. Iacovella, Sharon C. Glotzer
    Abstract:

    Recent simulations predict that aggregating nanospheres functionalized with polymer “tethers” can self-assemble to form the double Gyroid (DG) phase seen in block copolymer and surfactant systems. Within the struts of the Gyroid, the nanoparticles pack in icosahedral motifs, stabilizing the Gyroid phase in a small region of the phase diagram. Here, we study the impact of nanoparticle size polydispersity on the stability of the double Gyroid phase. We show for low amounts of polydispersity the energy of the double Gyroid phase is lowered. A large amount of polydispersity raises the energy of the system, disrupts the icosahedral packing, and eventually destabilizes the Gyroid. Our results show that the DG forms readily up to 10% polydispersity. Considering polydispersity as high as 30%, our results suggest no terminal polydispersity for the DG, but that higher polydispersities may kinetically inhibit the formation of phase. The inclusion of a small population of either smaller or larger nanospheres encourages low-energy icosahedral clusters and increases the Gyroid stability while facilitating its formation. We also introduce a new measure for determining the volume of a component in a microphase-separated system based on the Voronoi tessellation.

  • Local Ordering Of Polymer-Tethered Nanospheres And Nanorods And The Stabilization Of The Double Gyroid Phase
    The Journal of chemical physics, 2008
    Co-Authors: Christopher R. Iacovella, Mark A. Horsch, Sharon C. Glotzer
    Abstract:

    We present results of Brownian dynamics simulations of tethered nanospheres and tethered nanorods. Immiscibility between tether and nanoparticle facilitates microphase separation into the bicontinuous, double Gyroid structure (first reported by Iacovella et al. [Phys. Rev. E 75 (2007)] and Horsch et al. [J. Chem. Phys. 125 (2006)] respectively). We demonstrate the ability of these nanoparticles to adopt distinct, minimal energy local packings, in which nanospheres form icosahedral-like clusters and nanorods form splayed hexagonal bundles. These local structures reduce packing frustration within the nodes of the double Gyroid. We argue that the ability to locally order into stable structures is key to the formation of the double Gyroid phase in these systems.

J L Skinner - One of the best experts on this subject based on the ideXlab platform.

  • water dynamics in Gyroid phases of self assembled gemini surfactants
    Journal of the American Chemical Society, 2016
    Co-Authors: Santanu Roy, David R Skoff, Dominic V Perroni, Jagannath Mondal, Arun Yethiraj, Mahesh K Mahanthappa, Martin T Zanni, J L Skinner
    Abstract:

    Water-mediated ion transport through functional nanoporous materials depends on the dynamics of water confined within a given nanostructured morphology. Here, we investigate H-bonding dynamics of interfacial water within a "normal" (Type I) lyotropic Gyroid phase formed by a gemini dicarboxylate surfactant self-assembly using a combination of 2DIR spectroscopy and molecular dynamics simulations. Experiments and simulations demonstrate that water dynamics in the normal Gyroid phase is 1 order of magnitude slower than that in bulk water, due to specific interactions between water, the ionic surfactant headgroups, and counterions. Yet, the dynamics of water in the normal Gyroid phase are faster than those of water confined in a reverse spherical micelle of a sulfonate surfactant, given that the water pool in the reverse micelle and the water pore in the Gyroid phase have roughly the same diameters. This difference in confined water dynamics likely arises from the significantly reduced curvature-induced frustration at the convex interfaces of the normal Gyroid, as compared to the concave interfaces of a reverse spherical micelle. These detailed insights into confined water dynamics may guide the future design of artificial membranes that rapidly transport protons and other ions.

  • Water Dynamics in Gyroid Phases of Self-Assembled Gemini Surfactants
    Journal of the American Chemical Society, 2016
    Co-Authors: Santanu Roy, David R Skoff, Dominic V Perroni, Jagannath Mondal, Arun Yethiraj, Mahesh K Mahanthappa, Martin T Zanni, J L Skinner
    Abstract:

    Water-mediated ion transport through functional nanoporous materials depends on the dynamics of water confined within a given nanostructured morphology. Here, we investigate H-bonding dynamics of interfacial water within a “normal” (Type I) lyotropic Gyroid phase formed by a gemini dicarboxylate surfactant self-assembly using a combination of 2DIR spectroscopy and molecular dynamics simulations. Experiments and simulations demonstrate that water dynamics in the normal Gyroid phase is 1 order of magnitude slower than that in bulk water, due to specific interactions between water, the ionic surfactant headgroups, and counterions. Yet, the dynamics of water in the normal Gyroid phase are faster than those of water confined in a reverse spherical micelle of a sulfonate surfactant, given that the water pool in the reverse micelle and the water pore in the Gyroid phase have roughly the same diameters. This difference in confined water dynamics likely arises from the significantly reduced curvature-induced frust...

Andrei Zvelindovsky - One of the best experts on this subject based on the ideXlab platform.

  • Kinetic pathways of Gyroid-to-cylinder transitions in diblock copolymers under external fields: cell dynamics simulation
    Soft matter, 2008
    Co-Authors: Marco Pinna, Andrei Zvelindovsky
    Abstract:

    Using cell dynamics simulation we investigate the cubic Gyroid morphology of block copolymer melts under simple shear flow and electric field. The electric field should be stronger than a certain critical value to induce transition to a cylindrical phase. In the case of simple steady shear the Gyroid-to-cylinder transition was observed even for a very weak shear. Quantitative analysis of pathways of Gyroid-to-cylinder transition is performed by means of Minkowski functionals. We found that the kinetics of the Gyroid-to-cylinder transition are different under electric field and shear flow. Moreover, the Gyroid structure under different strengths of electric field shows different pathways. Different types of intermediates such as five-, four-fold connections and “winding” cylinders are found for different pathways.

  • Kinetic Pathway of Gyroid-to-Cylinder Transition in Diblock Copolymer Melt under an Electric Field
    Macromolecules, 2007
    Co-Authors: Takashi Honda, Toshihiro Kawakatsu, Andrei Zvelindovsky
    Abstract:

    Gyroid-to-cylinder transition in a diblock copolymer melt under an electric field is studied by real-space dynamical self-consistent-field theory. Starting from an equilibrium Gyroid structure, we apply an electric field along [111], [110], and [112] directions of the conventional unit cell of the Gyroid structure. Under sufficiently high value of the electric field, an epitaxial transition to cylinders occurs. Contrary to the case of a similar transition under the shear flow, we observe 5-fold connections as intermediates in the transition. We found a critical behavior of the lifetime of the initial Gyroid structure, which can be accounted for using the mean-field argument. Numerically obtained scattering function explains the unclarified intermediates experimentally observed in the thermal relaxation of a sheared Gyroid.

  • Mechanism of the transition between lamellar and Gyroid phases formed by a diblock copolymer in aqueous solution
    Langmuir : the ACS journal of surfaces and colloids, 2004
    Co-Authors: Ian W. Hamley, Valeria Castelletto, Oleksandr O. Mykhaylyk, Zhuo Yang, Roland P. May, Kateryna S. Lyakhova, G. J. Agur Sevink, Andrei Zvelindovsky
    Abstract:

    The mechanism of the transition from a lamellar phase to a Gyroid phase in an aqueous solution of a diblock copolymer has been studied by time-resolved synchrotron small-angle X-ray scattering. The transition occurs via a metastable perforated lamellar structure. The perforations initially have liquidlike ordering before developing hexagonal packing. The transient phase of irregularly perforated layers is revealed by the development of diffuse scattering peaks, just below the Bragg peaks of the lamellar structure. The diffuse scattering is modeled by Monte Carlo simulations of perforated layers. Following the formation of perforations, Bragg peaks characteristic of a hexagonal structure signal an ordering into a hexagonal lattice (with the concomitant loss of diffuse scattering). Computer simulations based on a dynamic density functional model reproduce these features. The hexagonal perforated lamellar phase is rapidly replaced by the Gyroid phase. The domain spacing of the Gyroid phase is larger than that of the perforated lamellar structure. The perforated lamellar and Gyroid phases coexist for a defined period. The reverse transition from Gyroid to lamellae occurs directly, with no transient or metastable intermediates.