3D Mesostructures Research Articles

Interaction of 3D mesostructures composed of Pd-Ni alloy nanowires with low-temperature oxygen plasma

We report that volumetric mesoporous structures obtained via self-organization of Pd-Ni nanowires interact actively with low temperature non-equilibrium oxygen plasma. This interaction leads to strong red incandescence of the composite nanostrucutures. After the plasma-chemical treatment, the X-ray diffraction pattern reveals presence of nanocrystalline nickel (II) oxide phase on surface of the samples. Measurements of electromagnetic response indicate that the samples exposed to oxygen plasma retain metallic type conductivity which is similar to the pristine Pd-Ni samples. Thus our studies indicate that the plasma-chemical treatment yields novel composite 3D hierarchical structures with a highly conductive skeleton of Pd-Ni nanowires covered by a thin nickel (II) oxide semiconducting layer of large surface area. These structures are attractive for applications.

Mechanically-Guided Deterministic Assembly of 3D Mesostructures Assisted by Residual Stresses.

Formation of 3D mesostructures in advanced functional materials is of growing interest due to the widespread envisioned applications of devices that exploit 3D architectures. Mechanically guided assembly based on compressive buckling of 2D precursors represents a promising method, with applicability to a diverse set of geometries and materials, including inorganic semiconductors, metals, polymers, and their heterogeneous combinations. This paper introduces ideas that extend the levels of control and the range of 3D layouts that are achievable in this manner. Here, thin, patterned layers with well-defined residual stresses influence the process of 2D to 3D geometric transformation. Systematic studies through combined analytical modeling, numerical simulations, and experimental observations demonstrate the effectiveness of the proposed strategy through ≈20 example cases with a broad range of complex 3D topologies. The results elucidate the ability of these stressed layers to alter the energy landscape associated with the transformation process and, specifically, the energy barriers that separate different stable modes in the final 3D configurations. A demonstration in a mechanically tunable microbalance illustrates the utility of these ideas in a simple structure designed for mass measurement.

Correction: Corrigendum: Printing, folding and assembly methods for forming 3D mesostructures in advanced materials

Nature Reviews Materials 2, 17019 (2017) In the originally published version of this article, there was an error in the Acknowledgements section. This has been corrected in both the HTML and PDF versions.

Kirigami pattern design of mechanically driven formation of complex 3D structures through topology optimization

Rapid, precise and controllable assembly of three-dimensional (3D) micro/nanostructures in advanced materials are attracting increasing interest in scientific research and engineering innovation due to its widespread applications. One of the notable approaches that can achieve mechanically driven assembly of 3D mesostructures is realized by applying compressive forces on two-dimensional (2D) micro/nanomembranes with strategically designed geometry and patterns of cuts. This approach is very effective to produce 3D mesostructures for prescribed cutting patterns, however, the inverse problem, that is finding the geometries and patterns of cuts which can lead to predefined desirable 3D morphologies, has not been well addressed yet. In this letter, a systematic approach that can solve the aforementioned inverse design problem is developed under the framework of topology optimization. Design examples provided demonstrate the effectiveness of the proposed approach.

Printing, folding and assembly methods for forming 3D mesostructures in advanced materials

A rapidly expanding area of research in materials science involves the development of routes to complex 3D structures with feature sizes in the mesoscopic range (that is, between tens of nanometres and hundreds of micrometres). A goal is to establish methods for controlling the properties of materials systems and the function of devices constructed with them, not only through chemistry and morphology, but also through 3D architectures. The resulting systems, sometimes referred to as metamaterials, offer engineered behaviours with optical, thermal, acoustic, mechanical and electronic properties that do not occur in the natural world. Impressive advances in 3D printing techniques represent some of the most broadly recognized developments in this field, but recent successes with strategies based on concepts in origami, kirigami and deterministic assembly provide additional, unique options in 3D design and high-performance materials. In this Review, we highlight the latest progress and trends in methods for fabricating 3D mesostructures, beginning with the development of advanced material inks for nozzle-based approaches to 3D printing and new schemes for 3D optical patterning. In subsequent sections, we summarize more recent methods based on folding, rolling and mechanical assembly, including their application with materials such as designer hydrogels, monocrystalline inorganic semiconductors and graphene. Emerging materials and methods for fabricating 3D micro- and nanostructures provide powerful capabilities of relevance across diverse areas of technology. This Review highlights the latest results and future trends associated with the most powerful methods in 3D printing, folding and assembly.

A combined-alpha-shape-implicit-surface approach to generate 3D random concrete mesostructures via digital image processing, spectral representation, and point cloud

Concrete aggregates have a random and complex shape, which has been shown to affect the mechanical properties of concrete. Commonly, they are approximated as spheres or polyhedra in 3D cases, or further simplified as circles or polygons in 2D cases. This study presents a numerical procedure for the stochastic characterization and representation of the aggregates and microcracks in concrete and the generation of virtual 3D random concrete mesostructures. Central to the proposed simulation method is the generation of realistic 3D aggregate point clouds based on an improved decomposition scheme and the conversion of the point clouds to 3D aggregate microstructures using a hybrid alpha-shape-implicit-surface algorithm. To optimize the simulation results, an image processing procedure and a set of representative aggregates are developed. It is shown that the proposed procedure is capable of reproducing high-quality concrete mesostructures with microcracks, which opens the door to unravelling complex microstructural behaviors of cement-based materials.

Embedded finite element formulation for the modeling of chloride diffusion accounting for chloride binding in meso-scale concrete

This paper presents the FE formulation for the numerical modelling of chloride ions diffusion accounting for the chloride binding capacity in meso-scale concrete. The finite element formulation is built through a discrete (lattice) finite element model and the meso-structure is based on a two-phase 3D representation of heterogeneous materials, such as concrete, where stiff aggregates are embedded into a mortar matrix. In order to take into account these heterogeneities in the mesh, we turn to the Embedded Finite Element Method (E-FEM). The E-FEM allows to use meshes not necessarily matching the physical interface (aggregates/mortar matrix) while retaining the accuracy of the classical finite element approach. This is achieved by introducing a weak discontinuity in the chloride concentration field for finite elements where the physical interface is present. A numerical solving strategy is presented to efficiently resolve the FE problem both in terms of chloride concentration field variables and weak discontinuity parameters. We investigate through 1D simulations the influence of the microstructure properties and the chloride binding capacity on the chloride concentration profiles. We show that taking explicitly into account the diffusion coefficients of the microstructure and the chloride binding capacity are important to consider for a better prediction of the time span until corrosion initiation. This is important for accurately estimating the service life of a structure. Numerical homogenization experiments are also performed on 3D meso-structures to compute macroscopic diffusivity tensors accounting for two-phase material. Comparison with Maxwell's equation are performed to show the accuracy of the proposed numerical approach.

Deterministic Self-Rolling of Ultrathin Nanocrystalline Diamond Nanomembranes for 3D Tubular/Helical Architecture.

Nanocrystalline diamond nanomembranes with thinning-reduced flexural rigidities can be shaped into various 3D mesostructures, such as tubes, jagged ribbons, nested tubes, helices, and nested rings. Microscale helical diamond architectures are formed by controlled debonding in agreement with finite-element simulation results. Rolled-up diamond tubular microcavities exhibit pronounced defect-related photoluminescence with whispering-gallery-mode resonance.

Engineered elastomer substrates for guided assembly of complex 3D mesostructures by spatially nonuniform compressive buckling.

Approaches capable of creating three-dimensional (3D) mesostructures in advanced materials (device-grade semiconductors, electroactive polymers etc.) are of increasing interest in modern materials research. A versatile set of approaches exploits transformation of planar precursors into 3D architectures through the action of compressive forces associated with release of prestrain in a supporting elastomer substrate. Although a diverse set of 3D structures can be realized in nearly any class of material in this way, all previously reported demonstrations lack the ability to vary the degree of compression imparted to different regions of the 2D precursor, thus constraining the diversity of 3D geometries. This paper presents a set of ideas in materials and mechanics in which elastomeric substrates with engineered distributions of thickness yield desired strain distributions for targeted control over resultant 3D mesostructures geometries. This approach is compatible with a broad range of advanced functional materials from device-grade semiconductors to commercially available thin films, over length scales from tens of microns to several millimeters. A wide range of 3D structures can be produced in this way, some of which have direct relevance to applications in tunable optics and stretchable electronics.

Mechanical assembly of complex, 3D mesostructures from releasable multilayers of advanced materials.

Capabilities for assembly of three-dimensional (3D) micro/nanostructures in advanced materials have important implications across a broad range of application areas, reaching nearly every class of microsystem technology. Approaches that rely on the controlled, compressive buckling of 2D precursors are promising because of their demonstrated compatibility with the most sophisticated planar technologies, where materials include inorganic semiconductors, polymers, metals, and various heterogeneous combinations, spanning length scales from submicrometer to centimeter dimensions. We introduce a set of fabrication techniques and design concepts that bypass certain constraints set by the underlying physics and geometrical properties of the assembly processes associated with the original versions of these methods. In particular, the use of releasable, multilayer 2D precursors provides access to complex 3D topologies, including dense architectures with nested layouts, controlled points of entanglement, and other previously unobtainable layouts. Furthermore, the simultaneous, coordinated assembly of additional structures can enhance the structural stability and drive the motion of extended features in these systems. The resulting 3D mesostructures, demonstrated in a diverse set of more than 40 different examples with feature sizes from micrometers to centimeters, offer unique possibilities in device design. A 3D spiral inductor for near-field communication represents an example where these ideas enable enhanced quality (Q) factors and broader working angles compared to those of conventional 2D counterparts.

Computational technology for analysis of 3D meso-structure effects on damage and failure of concrete

Methodology for analysis of meso-structure effects on longer-scale mechanical response of concrete is developed. Efficient algorithms for particle generation and packing are proposed to represent 3D meso-structures as collections of discrete features distributed randomly in a continuous phase. Specialised to concrete, the continuous phase represents mortar, while the features are aggregates and voids. Intra- and inter-phase cohesive zones are used for failure initiation and crack propagation. A Monte Carlo approach is proposed to analyse the effects of meso-structure geometrical (volume density, size distribution and shape of features) and physical (strength and energy of cohesive zones) properties, whereas a number of model realisations with identical properties are used for statistical analysis. The results present the relative significance of each meso-structure parameter for the emergent load capacity (tensile strength), damage evolution via micro-crack coalescence and macro-crack patterns, and failure energy density (toughness) of concrete. The proposed methodology is an effective tool for meso-structure optimisation in the design of concrete structures with prescribed requirements for strength and toughness.

A mechanically driven form of Kirigami as a route to 3D mesostructures in micro/nanomembranes

Assembly of 3D micro/nanostructures in advanced functional materials has important implications across broad areas of technology. Existing approaches are compatible, however, only with narrow classes of materials and/or 3D geometries. This paper introduces ideas for a form of Kirigami that allows precise, mechanically driven assembly of 3D mesostructures of diverse materials from 2D micro/nanomembranes with strategically designed geometries and patterns of cuts. Theoretical and experimental studies demonstrate applicability of the methods across length scales from macro to nano, in materials ranging from monocrystalline silicon to plastic, with levels of topographical complexity that significantly exceed those that can be achieved using other approaches. A broad set of examples includes 3D silicon mesostructures and hybrid nanomembrane-nanoribbon systems, including heterogeneous combinations with polymers and metals, with critical dimensions that range from 100 nm to 30 mm. A 3D mechanically tunable optical transmission window provides an application example of this Kirigami process, enabled by theoretically guided design.

Interfacial assembly of mesoporous nanopyramids as ultrasensitive cellular interfaces featuring efficient direct electrochemistry

A general method for assembling patterned interfaces of uniform, flexible mesoporous iron oxide nanopyramid islands (NPIs) is presented. The three-dimensional (3D) mesoporous iron oxide–NPI interfaces possess a unique mesostructure that features a large surface area (~158 m2 g−1), a large pore size (~18 nm) and excellent flexibility (can be folded 100 times). Furthermore, the 3D mesoporous Au–NPI interfaces allow efficient immobilization of cytochrome c (Cyt c; more than 165-fold increase) and a significant enhancement of localized surface plasmon resonance (~26-fold at 625 nm) compared with that of two-dimensional (2D) planar iron oxide films without nanopores. More importantly, the ultrasensitive integrated interfaces demonstrate over 1000-fold enhancement of the photocurrent variation on the 3D mesostructures based on the switchable direct electrochemistry of Cyt c. The strategy of interfacial assembly offers new possibilities for the chemical design of patterned mesoporous semiconductors with high flexibility and tailored photocatalytic characteristics. This investigation provides a novel paradigm for an unconventional 3D porous biointerface that can be used for sub-nanomolar level recognition of biomolecules (~0.2 nM for H2O2) and suggests the new concept of large-surface-area 3D mesostructure–protein interfaces as a step toward using direct electrochemistry for biomedical applications. Flexible lab-on-a-chip devices containing iron oxide nanopyramids may kick start new approaches to sub-nanomolar detection of biomolecules. A team of Chinese and Australian researchers led by Dongyuan Zhao from Fudan University used lithographic techniques to pattern surfaces with pointy iron oxide nanopyramids and gold nanoparticles and then loaded the protein cytochrome c (Cyt c). The three-dimensional, mesoporous cavities inside the nanopyramids boosted both cell attachment onto the device and the surface plasmon signals used for biosensing. When the team exposed the biointerface to solar light to initiate the Cyt c redox cycle, they saw a 1,000-fold enhancement in the photoelectrochemical current over typical interfaces. The magnitude of such solar-driven currents makes the device extremely sensitive — the researchers foresee direct monitoring of electrochemical transfer between proteins for real-time disease diagnostics. A general method for assembling patterned interfaces of uniform, flexible mesoporous iron oxide nanopyramid islands is presented. The 3D porous interfaces possess a unique mesostructure that features a large surface area, a large pore size and excellent flexibility. Furthermore, the 3D porous Au–NPI interfaces allow efficient immobilization of cytochrome c and a significant enhancement of localized surface plasmon resonance. More importantly, the ultrasensitive integrated interfaces demonstrate over 1000-fold enhancement of the photocurrent variation on the 3D mesostructures based on the switchable direct electrochemistry cytochrome c. The strategy of interfacial assembly offers new possibilities for the chemical design of patterned mesoporous semiconductors with high flexibility and tailored photocatalytic characteristics.

Rapid Thiol‐Yne‐Mediated Fabrication and Dual Postfunctionalization of Micro‐Resolved 3D Mesostructures

3D mesostructures with a height of up to 1 mm and micrometer feature size are fabricated employing a writing speed of 1 cm s−1 via direct laser writing utilizing a novel functional photoresist based on the radical coupling reaction of thiols and alkynes. The refractive index of the resist—consisting of a tetrafunctional thiol, a tetrafunctional alkyne and a photoinitiator—is tailored to be compatible with the employed high numerical aperture (NA) objective lens, thus enabling a Dip‐in configuration. Mesostructures are characterized by scanning electron microscopy, optical photography, and nondestructive 3D time‐of‐flight secondary ion mass spectrometry. Woodpile photonic crystals are fabricated as benchmark structures in order to investigate the axial resolution. Verification of the chemical fabrication mechanism is achieved via transmission Fourier transform infrared (FTIR) spectroscopy of fabricated cuboid structures by monitoring the decrease of corresponding thiol and alkyne absorption peaks. Postmodification reactions, namely the thiol‐Michael addition and the copper‐catalyzed azide alkyne cycloaddition, are conducted employing residual thiols and alkynes throughout the cuboid structures. Successful dual and orthogonal modification throughout the structure and on the surface is achieved and verified utilizing transmission FTIR spectroscopy and time‐of‐flight secondary ion mass spectrometry.

Template-directed assembly of metal-chalcogenide nanocrystals into ordered mesoporous networks.

Although great progress in the synthesis of porous networks of metal and metal oxide nanoparticles with highly accessible pore surface and ordered mesoscale pores has been achieved, synthesis of assembled 3D mesostructures of metal-chalcogenide nanocrystals is still challenging. In this work we demonstrate that ordered mesoporous networks, which comprise well-defined interconnected metal sulfide nanocrystals, can be prepared through a polymer-templated oxidative polymerization process. The resulting self-assembled mesostructures that were obtained after solvent extraction of the polymer template impart the unique combination of light-emitting metal chalcogenide nanocrystals, three-dimensional open-pore structure, high surface area, and uniform pores. We show that the pore surface of these materials is active and accessible to incoming molecules, exhibiting high photocatalytic activity and stability, for instance, in oxidation of 1-phenylethanol into acetophenone. We demonstrate through appropriate selection of the synthetic components that this method is general to prepare ordered mesoporous materials from metal chalcogenide nanocrystals with various sizes and compositions.

Materials science. Assembly of micro/nanomaterials into complex, three-dimensional architectures by compressive buckling.

Complex three-dimensional (3D) structures in biology (e.g., cytoskeletal webs, neural circuits, and vasculature networks) form naturally to provide essential functions in even the most basic forms of life. Compelling opportunities exist for analogous 3D architectures in human-made devices, but design options are constrained by existing capabilities in materials growth and assembly. We report routes to previously inaccessible classes of 3D constructs in advanced materials, including device-grade silicon. The schemes involve geometric transformation of 2D micro/nanostructures into extended 3D layouts by compressive buckling. Demonstrations include experimental and theoretical studies of more than 40 representative geometries, from single and multiple helices, toroids, and conical spirals to structures that resemble spherical baskets, cuboid cages, starbursts, flowers, scaffolds, fences, and frameworks, each with single- and/or multiple-level configurations.

Popping materials and devices from 2D into 3D

Materials Science Curved, thin, flexible complex three-dimensional (3D) structures can be very hard to manufacture at small length scales. Xu et al. develop an ingenious design strategy for the microfabrication of complex geometric 3D mesostructures that derive from the out-of-plane buckling of an originally planar structural layout (see the Perspective by Ye and Tsukruk). Finite element analysis of the mechanics makes it possible to design the two 2D patterns, which is then attached to a previously strained substrate at a number of points. Relaxing of the substrate causes the patterned material to bend and buckle, leading to its 3D shape. Science , this issue p. [154][1]; see also p. [130][2] [1]: /lookup/doi/10.1126/science.1260960 [2]: /lookup/doi/10.1126/science.aaa2643

Prediction of Creep Properties of Fiber-Reinforced Closed-Cell Metallic Foams

The anti-creep capability of metallic foams is important to structural applications at elevated temperatures. Currently, available creep models for opened-cell foam materials are usually derived by rather simplified meso-structural models. Here, we try to predict the creep properties of new fiber-reinforced closed-cell foams with more realistic 3D meso-structures. In the study, three-dimensional Voronoi structures are constructed to describe the inner structure of closed-cell foams, and reinforcing fibers are modeled by line segments penetrating through cell walls. Based on the recommended model, not only the steady creep strain rates of both the unreinforced and the reinforced foam materials are well predicted with considering the effects of temperature, stress, and relative density, but also the creep evolution features of metal foam are revealed from the meso-deformation behaviors. It is found that, at moderate temperature and stress, the creep rate of the fiber-reinforced metallic foam can also be well described by a power law with respect to the foam relative density. The influence of addition of fibers on the creep properties is parametrically studied and it is shown that addition of fibers has a positive effect on restricting the creep rate. It is observed that during creep, the stresses of cell walls are redistributed and become more homogeneous with time. When the creep rate of metallic foam reaches steady state depends on when the stresses of cell walls become homogeneous.

Visual monitoring and removal of divalent copper, cadmium, and mercury ions from water by using mesoporous cubic Ia3d aluminosilica sensors

The design of a simple, pH-dependent, micro-object optical sensor based on mesoporous Ia3d aluminosilica pellets functionalized by a porphyrinic chelating ligand for the monitoring and removal of ultra-trace levels of toxic metals, such as Hg(II), Cu(II), and Cd(II), from aqueous media, such as drinking water and biological fluids, is described in this study. This micro-object optical sensor has large surface area-to-volume ratios and uniformly shaped pores in three-dimensional (3D) nanoscale gyroidal structures, and its active sites consist of heteroatoms arranged around uniformly shaped pores in 3D nanoscale gyroidal mesostructures. These mesostructures are densely coated with chelating ligand to permit ultra-fast, specific, pH-dependent visualization and the removal of toxic metals at sub-picomolar concentrations (∼10−11moldm−3) from aqueous media, including drinking water and a suspension of red blood cells, via a colorimetric signal visible to the naked eye, as well as via UV–Vis reflectance spectroscopy. The adsorption of metal ions forms a monolayer on the interior pore surfaces of the pellets in this sensor system. Given that the pellets exhibit long-term stability, reproducibility, and versatility over a number of analysis/regeneration cycles, they can be useful for the fabrication of inexpensive sensor devices for naked-eye detection of toxic pollutants. Furthermore, the usage of the pellets to remove metal ions from a physiological fluid (i.e., blood cells) was evaluated.

Synthesis of Three-Dimensional Mesostructured Graphitic Carbon Nitride Materials and their Application as Heterogeneous Catalysts for Knoevenagel Condensation Reactions

Three-dimensional (3D) mesostructured graphitic carbon nitride materials with tunable surface areas (394–498 m2 g−1) and pore volumes (0.54–1.36 cm3 g−1) were synthesized through a nanocasting method. Mesocellular silica foam (MCF) was used as a template, and carbon tetrachloride (CTC) and ethylenediamine (EDA) were used as precursors. The effect of the ratio of the two precursors (EDA/CTC) on the textural properties and chemical compositions of the CN-MCF samples were investigated by several characterization techniques. The results revealed that the 3D mesostructures were maintained when the ratio of EDA/CTC was greater than 0.4. Among the different CN-MCF materials prepared, CN-MCF-0.4 demonstrated the highest catalytic performance for Knoevenagel condensation reactions, mainly because of its high amount of surface N, high surface area, and large pore volume. In addition, the CN-MCF-0.4 catalyst showed good stability as well as versatility for various substrates. Mesostructured graphitic carbon nitride materials have been synthesized using MCF as template and the effects of the ratios of the N & C precursors on their physicochemical properties have been comparatively investigated; the materials demonstrate effective and versatile catalytic performance for a series of Knoevenagel condensation reactions.