Open Lattice Structure Research Articles

Co-doped Ni-PBA anchored on optimized ZIF-67-derived Co/N-doped hollow carbon framework for high-performance hybrid capacitive deionization

Prussian blue analogues (PBAs) are considered to be a promising electrode material for hybrid capacitive deionization (HCDI) due to their open lattice structure, adjustable composition and high theoretical capacity. Nevertheless, the performance of PBAs in practical applications is limited by their low intrinsic conductivity and structural degradation. Herein, we demonstrate an advanced heterostructure CoNi-PBA@Co/N-HC by anchoring cobalt-doped nickel hexacyanoferrate (CoNi-PBA) on cobalt/nitrogen-doped hollow porous carbon (Co/N-HC) derived from cobalt-based metal–organic frameworks (ZIF-67). Co/N-HC as the conductive growth framework of CoNi-PBA can not only promote the rapid charge transfer and efficient ion diffusion, but also mitigate the structural degradation of CoNi-PBA crystals during ion intercalation/deintercalation. Moreover, the doped Co in CoNi-PBA is derived from Co/N-HC, allowing the heterostructures to form more stable and tighter interconnections. Therefore, the optimal PBA@Co/N-HC300 electrode exhibits reduced equivalent series resistance (Rs 1.10 Ω < Rs (PBA) 1.41 Ω), enhanced ion diffusion rate (DNa+ 2.86 × 10−16 > DNa+(PBA) 4.65 × 10−18) and exceptional electrochemical stability (99% capacitance retention, 500 times CV tests). Correspondingly, the HCDI cell PBA@Co/N-HC300//Co/N-HC demonstrates good Na+ removal capacity (33.37 mg·g−1), excellent charge efficiency (83.65%), diminished energy consumption (0.657 kWh kg−1-NaCl) and improved cycle stability (90.8% capacity retention, 40 cycles).

Light-Driven, Dynamic Assembly of Micron-To-Centimeter Parts, Micromachines and Microbot Swarms.

This work describes light-driven assembly of dynamic formations and functional particle swarms controlled by appropriately programmed light patterns. The system capitalizes on the use of a fluidic bed whose low thermal conductivity assures that light-generated heat remains "localized" and sets strong convective flows in the immediate vicinity of the particles being irradiated. In this way, even low-power laser light or light from a desktop slide projector can be used to organize dynamic formations of objects spanning four orders of magnitude in size (from microns to centimeters) and over nine orders of magnitude in terms of mass. These dynamic assemblies include open-lattice structures with individual particles performing intricate translational and/or rotational motions, density-gradient particle arrays, nested architectures of mechanical components (e.g., planetary gears), or swarms of light-actuated microbots controlling assembly of other objects.

Effect of microwave heating on the interdiffusion in BaTiO3–SrTiO3 binary ceramic system

An investigation on the effect of microwave heating (2.45 GHz) on the interdiffusion process was carried out and compared with conventional heating for BaTiO3–SrTiO3 binary system in the temperature range of 1200–1400 °C. Interdiffusion coefficients were extracted using Boltzmann–Matano analysis for both heating methods. Consequently, microwave heating was determined to result in higher interdiffusion coefficients compared to conventional heating. Correspondingly, ∼27% decrease in the apparent activation energy of interdiffusion was found which was associated with faster diffusion under electromagnetic irradiation due to increased vacancy concentration and more open lattice structure in Ba-rich regions which could be exploited for unique experimentations and non-equilibrium/non-stoichiometric phase transformations to study their kinetics and formation mechanisms and grasp a better understanding on the dielectric properties of such perovskites.

PoroFluidics: deterministic fluid control in porous microfluidics.

Microfluidic devices with open lattice structures, equivalent to a type of porous media, allow for the manipulation of fluid transport processes while having distinct structural, mechanical, and thermal properties. However, a fundamental understanding of the design principles for the solid structure in order to achieve consistent and desired flow patterns remains a challenge, preventing its further development and wider applications. Here, through quantitative and mechanistic analyses of the behavior of multi-phase phenomena that involve gas-liquid-solid interfaces, we present a design framework for microfluidic devices containing porous architectures (referred to as poroFluidics) for deterministic control of multi-phase fluid transport processes. We show that the essential properties of the fluids and solid, including viscosity, interfacial tension, wettability, as well as solid manufacture resolution, can be incorporated into the design to achieve consistent flow in porous media, where the desired spatial and temporal fluid invasion sequence can be realized. Experiments and numerical simulations reveal that different preferential flow pathways can be controlled by solid geometry, flow conditions, or fluid/solid properties. Our design framework enables precise, multifunctional, and dynamic control of multi-phase transport within engineered porous media.

The ultra-thin, minimally invasive surface electrode array NeuroWeb for probing neural activity

Electrophysiological recording technologies can provide valuable insights into the functioning of the central and peripheral nervous systems. Surface electrode arrays made of soft materials or implantable multi-electrode arrays with high electrode density have been widely utilized as neural probes. However, neither of these probe types can simultaneously achieve minimal invasiveness and robust neural signal detection. Here, we present an ultra-thin, minimally invasive neural probe (the “NeuroWeb”) consisting of hexagonal boron nitride and graphene, which leverages the strengths of both surface electrode array and implantable multi-electrode array. The NeuroWeb open lattice structure with a total thickness of 100 nm demonstrates high flexibility and strong adhesion, establishing a conformal and tight interface with the uneven mouse brain surface. In vivo electrophysiological recordings show that NeuroWeb detects stable single-unit activity of neurons with high signal-to-noise ratios. Furthermore, we investigate neural interactions between the somatosensory cortex and the cerebellum using transparent dual NeuroWebs and optical stimulation, and measure the times of neural signal transmission between the brain regions depending on the pathway. Therefore, NeuroWeb can be expected to pave the way for understanding complex brain networks with optical and electrophysiological mapping of the brain.

3D Printed Lattice Template by Material Extrusion Technique for Fabrication of Pixelated Photodetector.

Rigid and flexible, pixelated ultraviolet photodetectors (PD) based on ZnO have been fabricated by material extrusion 3D printing technique. The photoresponse is studied in an out-of-plane configuration. An open lattice structure is printed using PLA over ITO/Glass substrate for rigid, and TPU over ITO/PET substrate for flexible PDs. ZnO slurry is filled selectively into the columnar matrix by the microdispensing technique. The optical detector printed on ITO/Glass substrate shows a sensitivity of 25 and responsivity of 1.55 nA/mW with a rise and decay time of 1.6 and 0.6 s, respectively. Similarly, the flexible PD printed using TPU lattice shows a sensitivity of 9.5 and responsivity of 0.38 nA/mW with a rise and decay time of 1.8 and 0.6 s, respectively. The charge transport mechanism is studied using band diagram analysis. 3D printed open lattice structure is found to be a potential template for sensor fabrication. This work demonstrates the capability of material extrusion 3D printing with an open lattice structure for the fabrication of high-resolution pixelated PDs.

On Liquid Flow Maldistribution through Investigation of Random Open-Structure Packings

The optimal design of packed columns for separation processes is strongly dependent on an accurate prediction of the fluid flows in the packing. Insufficient knowledge about the complex factors and mechanisms governing hydrodynamic effects is compensated for by empirical information. The present study fills the gap in experimental data about the liquid phase distribution in plastic Raschig Super-Ring (RSRP) packing and plastic Ralu–Flow (RF) packing. These belong to the family of widely used random packings with an open lattice structure characterized by high mass transfer efficiency and a low pressure drop. The study was performed using the liquid collection method with a device with concentric annular collection sections at the packing outlet. Large-scale liquid maldistribution in the central and peripheral zones of the packed bed were evaluated in comparison data on competing random and structured packings. The effects of the packing size and the liquid load on the radial distribution of the superficial liquid velocity, wall flow formation and the maldistribution factor were investigated and analyzed. The results contribute to deepening the knowledge about the phenomenon of large-scale liquid flow maldistribution in packed columns, as well as to design enhancement.

Numerical Simulation and Experimental Study on Gas Flow in an Open Lattice Structure for an Advanced Space Nuclear Power System

Helium flow in the rod bundle channel with an open lattice structure is an important phenomenon for the advanced gas-cooled nuclear core design. In this study, thermal analysis with helium flow in various channel designs is conducted based on CFD methods to determine a dimension-optimized rod bundle channel. An experimental study then follows in order to pick up an appropriate gas flow model in further numerical simulation. Finally, helium flow in the bundle channels consisting of 217 rods is simulated using this chosen flow model, which shows to satisfy the requirements of basic thermal analysis of a newly designed gas-cooled reactor with an open lattice structure. Generally, this work will contribute to the design and analysis of the future advanced space nuclear power system.

A novel nature inspired 3D open lattice structure for specific energy absorption

Energy absorption is a key performance criterion for several engineering structures. Lightweight lattice structures are better suited for this purpose. The convolute design patterns that exist in nature are proven effective for several engineering applications. In this paper, a George lily flower leaf is considered to build a novel 3D open lattice pattern for specific energy absorption (SEA) purposes. A multi-cellular specimen is designed and fabricated using Vat photopolymerization 3D printing process. Quasi-static compression tests have been conducted and the performance of proposed structure is compared with 2.5D closed thin-walled structures and found the proposed 3D open lattice structure has shown significant improvement in SEA over other thin-walled structures.

Numerical and experimental investigations of novel nature inspired open lattice cellular structures for enhanced stiffness and specific energy absorption

Lattice structures are meant for light weight structure with a high strength to weight ratio used to carry high loads and high energy absorption capabilities. In the lattice structures, the non-stochastic arrangement of members has the ability to control and customize their mechanical properties. The recent developments in additive manufacturing provides freedom in design and gives flexibility to manufacture tailored complex novel lattice structures. In the present investigation, the traditional 2.5D honeycomb and the tessellated open lattice structures with basic crystalline arrangements of the members are considered to study the load carrying capacity, stiffness and energy absorption capabilities by keeping constant volume for each lattice. The results through the experiments and finite element analysis are compared with a novel open lattices structure to show significant improvement in stiffness and high energy absorption with the volume of the material. However, the novel open lattice structure has displayed prominent post yield plateau stresses and energy absorption with sacrificing stiffness and strength significantly.

Scalable, process-oriented beam lattices: generation, characterization, and compensation for open cellular structures.

Additively manufactured lattices are emerging as promising candidates for structural, thermal, chemical, and biological applications. However, achieving a satisfactory prototype or final part with this level of complexity requires synthesis of disparate knowledge from the distinctly digital and physical processing stages. This work proposes an integrated framework for processing self-supporting, open lattice structures that do not require supports and facilitate material removal in post-processing steps. We describe a minimal yet comprehensive design strategy for generating uniform lattice structures with conformal open lattice skins for an arbitrary unit cell configuration. Using continuous liquid interface production (CLIP™) on a Carbon M1, printability is evaluated for five unique bending-dominated lattice structures at unit cell length scales from 0.5 - 3.5 mm and strut diameters ranging from 0.11 - 1.05 mm. Using a cubic lattice as a basis, we further examine dimensional fidelity with respect to 2D lattice void dimensions and part position, finding differences between length scales and within parts, due to physical processing artifacts. Finally, we demonstrate a functional grading strategy based on process control methods to compensate for dimensional deviations. Using an iterative approach based on a naïve process model, deviation of the planar strut radius in a cubic lattice was decreased by approximately 85% after two iterations. These insights and strategies can be readily applied to other structures, characterization techniques, and additive manufacturing processes, thereby improving the exchange of information between digital and physical processing and lowering the energy barriers to producing high-quality lattice parts.

Core-shell hybrid pre-preg tow for lightweight composite truss

A robust pre-impregnated hybrid tow for manufacturing lightweight composite truss has been developed and characterized. The hybrid tow is in a core-shell structure where the core is epoxy pre-impregnated carbon fibers and shell is a protective braided jacket. The hybrid tow has good conformability which allows it to be used in braiding process for fabricating complex shape lattice structures. The mechanical properties of the hybrid tow are essential for modeling and designing of open lattice structures. The paper studies the experimentations on the hybrid tow to obtain mechanical properties including tensile modulus and strength, short beam shear modulus and strength, flexural modulus and strength, torsional modulus, and strength. The corresponding experiments contain tensile test, 3-point bending test, and torsion test. The least square method is employed to differentiate short beam shear and bending. Microscopic images of the cross-section were taken to study volume fraction via digital image processing. Mechanical properties and volume fractions of the tow were measured by the proposed experimental methods in this paper to provide insights of manufacture processes as well as multiscale modeling of open lattices.

Excellent synaptic behavior of lithium-based nano-ionic transistor based on optimal WO2.7 stoichiometry with high ion diffusivity

In this study, we introduce a lithium (Li) ion-based three-terminal (3-T) synapse device using WOx as a channel. Our study reveals a key stoichiometry of WO2.7 for excellent synaptic characteristics that is related to Li-ion diffusivity. The open-lattice structure formed by oxygen deficiency promoted Li-ion injection and diffusion. The optimized stoichiometry and improved Li-ion diffusivity were confirmed by x-ray photoelectron spectroscopy analysis and cyclic voltammetry, respectively. Furthermore, the transient conductance change that inevitably occurs in ion-based synaptic transistors was resolved by applying a two-step voltage pulse scheme. As a result, we achieved a symmetric and linear weight-update characteristic with reduced program/erase operation time.

Effect of joint stiffness on torsional stiffness of open lattice composite structures

In open lattice composite structures, the lattice components are chemically bonded, which affects the overall properties of the structure. This study examines the effects of chemically bonded joints on the torsional stiffness of tubular lattice composite structures. Tubular open lattice structures, known as the open-architecture composite structures, are manufactured by braiding the impregnated carbon fiber tows. Samples were prepared with no chemically bonded and with epoxy joints using braid angles of 35°, 45°, and 67.5°. A finite element model of the open-architecture composite structures is developed to examine the mechanical behavior under torsion. It is shown that there is a significant difference between the samples with no-bonding joints and samples with epoxy joints in terms of torsional stiffness. Torsional stiffness of the structure is retained at 97%, 96%, and 93% of the theoretical limit for 35°, 45°, and 67.5° braid angles, respectively, when joint stiffness is ten times the component stiffness. Torsional stiffness is only 32%, 22%, and 13% of the theoretical limit for 35°, 45°, and 67.5° braid angles, respectively, when joint stiffness is one-10th of the component stiffness. The epoxy bonding at the intersection achieves 72% of the theoretical torsional stiffness of the “perfect joint” for 45° braid angle when joint stiffness is equal to the component stiffness. The finite element model is validated by experimental results. It can be concluded from the finite element analysis and experimental testing that the stiffness of the bonding joints has significant impact on the overall torsional stiffness of the biaxial composite lattice.

Experimental determination of the two-dimensional aerodynamic admittance of typical bridge decks

In this paper, the two-dimensional lift, drag and pitching moment aerodynamic admittances of three typical bridge deck sections, including a streamlined box section, an edge section and a truss section are identified by wind tunnel tests using a statistical identification approach and high-frequency dynamic balance measurement technique. An empirical formula for determining the two-dimensional aerodynamic admittance is proposed and compared with the commonly used Sears function and Davenport function. The results show that the two-dimensional lift and moment aerodynamic admittances for the three types of bridge decks are larger than Sears’ function in the concerned wavenumber range of the buffeting analysis. This indicates that the Sears function may underestimate the vertical and torsional buffeting response of prototype long-span bridges. The two-dimensional drag aerodynamic admittance of the truss section corresponds strongly with Davenport’s function, which verifies the reasonableness of Davenport’s function that was originally developed for the two-dimensional drag aerodynamic admittance of open lattice structures. Furthermore, it was found that the two-dimensional aerodynamic admittance is insensitive to the mean wind velocity. The effect of wind attack angle on the two-dimensional aerodynamic admittance of bridge decks cannot be neglected.

Precise Tubular Braid Structures of Ultrafine Microwires as Neural Probes: Significantly Reduced Chronic Immune Response and Greater Local Neural Survival in Rat Cortex.

Braided multi-electrode probes (BMEPs) for neural interfaces comprise ultrafine microwire bundles interwoven into tubular braids. BMEPs provide highly flexible probes and tethers, and an open lattice structure with up to 24 recording/stimulating channels in precise geometries, currently all within a [Formula: see text] diameter footprint. This paper compares the long-term tissue effects of BMEPs ( [Formula: see text] wires) versus single conventional 50- [Formula: see text] wires, by testing nearby chronic immune response and neural survival in rat cortex. Four different types of electrodes were implanted in cortex in each of eight rats: 1) BMEP with tether; 2) tethered 50- [Formula: see text] wire; 3) BMEP without a tether; and 4) untethered 50- [Formula: see text] wire. Quantitative immunohistological statistical comparisons after eight weeks using GFAP, ED1, and NeuN staining clearly showed that both BMEP implants had significantly less tissue immune response and more neuronal survival than either of the 50- [Formula: see text] wires ( ) in each of the eight rats. Data strongly indicate that BMEP tissue responses are superior, and that BMEP designs partly alleviate chronic tissue inflammatory responses and neural losses. The flexible body, tether and open braid lattice, and finer wire diameters of BMEP designs may all contribute to reducing the biological long-term response.

Compressive failure of a carbon nano-tesseract: Sci-Fi inspired materials and the strength of thanos

Inspired by the super-materials of science fiction (“sci-fi”), here we probe the stability and strength of a proposed all-carbon nano-tesseract or hypercube projected into 3D space, a so-called hypercubyne. The nanostructure is compared to other, similar carbon geometries of similar size, including a fullerene, a hypercubane, and a pentatope. The hypercube configurations provide high compressive strength and elastic toughness with an open lattice structure. For the all-carbon hypercubyne, initial failure is characterized by a buckling instability. Using the ultimate strength of hypercubyne as a basis, we proceed to predict the lower bound of the strength of the supervillain Thanos, who has been depicted destroying the Tesseract in the Marvel Cinematic Universe. Thanos has a minimum grip strength of over 40,000 tons, which is approximately 750,000 times that of a typical man. While such comic-inspired analysis is whimsical by design, the study sheds light into the behavior of future exotic carbon constructs and geometries, and illustrates the potential field of “sci-fi” inspired materials.

Photoelectric covalent organic frameworks: converting open lattices into ordered donor-acceptor heterojunctions.

Ordered one-dimensional open channels represent the typical porous structure of two-dimensional covalent organic frameworks (COFs). Here we report a general synthetic strategy for converting these open lattice structures into ordered donor-acceptor heterojunctions. A three-component topological design scheme was explored to prepare electron-donating intermediate COFs, which upon click reaction were transformed to photoelectric COFs with segregated donor-acceptor alignments, whereas electron-accepting buckyballs were spatially confined within the nanochannels via covalent anchoring on the channel walls. The donor-acceptor heterojunctions trigger photoinduced electron transfer and allow charge separation with radical species delocalized in the π-arrays, whereas the charge separation efficiency was dependent on the buckyball content. This new donor-acceptor strategy explores both skeletons and pores of COFs for charge separation and photoenergy conversion.

Use of a Large Crane for Wind and Tracer Profiles in an Urban Setting

Abstract Although measured vertical profiles of wind, turbulence, and tracer concentrations are critical for understanding the urban boundary layer, it is problematic to field a sounding system or a tall structure to support anemometers in a densely populated area. Anemometers mounted on an existing building may be measuring flow distorted by that building. During the Joint Urban 2003 field experiment in Oklahoma City, the authors solved these problems by using a large crane to support a cable and crossarm framework holding a vertical array of eight 3D sonic anemometers. The highest level was over 80 m above the surface; the lowest was just under 8 m. The open-lattice structure of the crane boom and skeletal array framework did not substantially alter the airflow to the sensors. Review of the spectra shows that there are no consistent oscillations in the wind data. Data were accepted from all azimuths, although the flow was from the south 80% of the time. Profiles of wind show pronounced curvature, indicating that the higher levels may be affected by rougher surfaces at a great distance from the crane. This crane-lofted system was safely erected and disassembled in a few hours, stood undisturbed for 34 days, and collected over 1500 separate profiles of 30-min averages.

A Theoretical Investigation of the Yield-to-Damage Enhancement with Polyatomic Projectiles in Organic SIMS

Experiments show that polyatomic projectiles have the potential to improve the sensitivity of organic secondary ion mass spectrometry by increasing the yield without a comparable increase in damage to the sample. Molecular dynamics simulations of the high energy bombardment of an organic film have been performed with the purpose of understanding how the yield-to-damage ratio is enhanced with polyatomic projectiles. The model systems consist of 0.6 keV Xe and SF5 projectiles bombarding a monolayer of biphenyl molecules on two different substrates, Cu(100) and Si(001). The yield-to-damage ratio is the ratio of the yield, defined as the number of molecules ejected stable and intact, to the damage, defined as the sum of molecules ejected either fragmented or unstable. To have a quantity that is comparable to the experimental definition of damage cross section, a yield-to-disappearance ratio, defined as the ratio of the yield to the sum of the yield and damage, is also calculated. The enhancements in both the yield-to-damage and yield-to-disappearance ratios show the same trends, with the greatest enhancement on the substrate with the open lattice structure and the lighter mass atoms, 12Si(100). Polyatomic projectiles are able to increase the yield more than the damage because different types of motion are responsible for the production of the two types of molecules. The yield is enhanced when the polyatomic projectile deposits energy into upward moving substrate atoms over a wider surface area, which leads to a greater number of intact and stable molecules ejected from the surface. Damage to molecules is caused primarily by the impact of the bombarding projectile.