3D Mats Research Articles

Use of high-performance turf reinforcement Mats for erosion protection

High-Performance Turf Reinforcement Mats (HPTRM) are a specific type of geocomposite used for erosion protection. These innovative products are 3D mats made up mainly of synthetic fibers, which are combined with synthetic or metallic reinforcement to create a strong, durable material that can withstand the forces of water and soil movement. Their purpose is to enhance the topsoil resistance and support the natural vegetation of a slope. HPTRMs serve multiple purposes. They act as physical barriers, absorbing water, and wind impact on soil. They also curtail soil loss, fostering vegetation growth, and augmenting superficial soil layer shear strength. Critical to achieving a successful application, is that the TRM allows for fast and durable re-vegetation. The 3D open weave structure of the matting provides the soil with stability and grants plant root establishment. This contributes to slope stabilization and erosion prevention. Further, these mats retain moisture, fundamental for vegetation growth in dry environments. Over the years, the use of HPTRM is gaining popularity in several different applications. In this paper, we will illustrate three different applications. The first one is a soil veneer reinforcement on a long slope, where the HPTRM provided increased shear stress to prevent sliding of the topsoil in extreme weather conditions. The second is an installation in a hydraulic application as a soft armor lining. The third is a soil nailing application, where the HPTRM has been used in combination with anchors to improve the stability of a steep slope.

Aerosol mediated localized dissolution to enhance the electrical behavior and sensitivity of piezoresistive nanofiber-based flexible sensors

This work proposes the use of solvents in the form of small size droplets to improve the connections among nanofibers (NFs) in electrospun composite nanofibers with carbon nanotube multiwalled (MWCNT) by improving the electrical and piezoresistive behavior of such electrically conductive polymer composites. The here proposed Aerosol Mediated Localized Dissolution (AMLD) process has been shown to be effective in improving the 3D microporous NF mat by inducing local dissolution that is effective in improving the connections among fibers within the mat. The AMLD process is demonstrated here for polyethylene oxide (PEO) / MWCNTs composite nanofibers, showing that the electrical conductivity is particularly improved in those samples with low content of MWCNTs, even below the original percolation threshold. The improved electrical conductivity is coupled with exceptional sensitivity of the flex sensor for low MWCNTs contents, this is particularly due to the ability of the AMLD process to preserve the high surface area of the 3D mat by inducing better fiber-to-fiber contacts in few regions only. In addition, this work demonstrates the effectiveness of applying an electrical potential difference during the AMLD process to improve the alignment of MWCNTs within the 3D microporous NF mat. The combination of voltage and AMLD allow to obtain a gauge factor as high as 571.9 with a MWCNTs loading of 1 wt%.

Experimental Study on Anti-Scour Property and Erosion Resistance of 3D Mat Materials for Slope Protection in Waterway Engineering

3D mats are environmentally friendly and ecological materials for protecting river and waterway banks. The anti-scour properties of the materials and the erosion resistance of the soil under them can be studied to provide decision support for the selection of slope protection materials and their applicable areas. In this paper, an indoor prototypical scouring experiment with a flume is carried out to study the anti-scour properties of three types of 3D mat materials (vegetation grass mats, Enkamat and reinforced Mike mat) and the erosion resistance of the underlying soil under typical combined conditions of flow rate and water stage. It is concluded that the 3D mats increase the resistance coefficient of the bed surface, and that with the same incoming flow, the average flow velocity is inversely related to the resistance coefficient. There are three scouring modes for 3D mats under the action of water flow: material failure caused by mechanical damage, performance failure caused by serious erosion of the soil mass and non-failure. Of the three mat materials, the reinforced Mike mats are more resistant to scouring than the other two unreinforced materials, and the erosion volume ratios of reinforced Mike mats, vegetation grass mats and Enkamat are 59.24%, 61.81% and 62.17%, respectively, under the same small flow rate and high water stage. The results show that the reinforced Mike mats have the best anti-scour property and soil conservation performance, followed by Enkamat and the vegetation grass mats. In addition, reinforced materials outperform non-reinforced ones in their anti-scour performance and their protection for the underlying soil on the bank slope.

A Systematic Review of Non-Pharmacological Interventions to Improve Gait Asymmetries in Neurological Populations

Gait asymmetries are commonly observed in neurological populations and linked to decreased gait velocity, balance decrements, increased fall risk, and heightened metabolic cost. Interventions designed to improve gait asymmetries have varying methods and results. The purpose of this systematic review was to investigate non-pharmacological interventions to improve gait asymmetries in neurological populations. Keyword searches were conducted using PubMed, CINAHL, and Academic Search Complete. The search yielded 14 studies for inclusion. Gait was assessed using 3D motion capture systems (n = 7), pressure-sensitive mats (e.g., GAITRite; n = 5), and positional sensors (n = 2). The gait variables most commonly analyzed for asymmetry were step length (n = 11), stance time (n = 9), and swing time (n = 5). Interventions to improve gait asymmetries predominantly used gait training techniques via a split-belt treadmill (n = 6), followed by insoles/orthoses (n = 3). The literature suggests that a wide range of methods can be used to improve spatiotemporal asymmetries. However, future research should further examine kinematic and kinetic gait asymmetries. Additionally, researchers should explore the necessary frequency and duration of various intervention strategies to achieve the greatest improvement in gait asymmetries, and to determine the best symmetry equation for quantifying gait asymmetries.

Wastewater Remediation Technologies Using Macroscopic Graphene-Based Materials: A Perspective

Three-dimensional (3D) graphene-based macrostructures are being developed to combat the issues associated with two-dimensional (2D) graphene materials in practical applications. The 3D macrostructures (3DMs), for example, membranes, fibres, sponges, beads, and mats, can be formed by the self-assembly of 2D graphene-based precursors with exceptional surface area and unique chemistry. With rational design, the 3D macrostructures can then possess outstanding properties and exclusive structures. Thanks to various advantages, these macrostructures are competing in a variety of applications with promising performances unlike the traditional activated carbons, biochars and hydrochars, which have less flexibilities for modifications towards versatile applications. However, despite having such a wide range of applications, 3DMs remain applicable on laboratory scale due to the associated factors like cost and extensive research. This perspective provides an overview of available graphene-based macrostructures and their diverse synthesis protocols. In the synthesis, hydrothermal route, chemical vapor deposition (CVD), wet spinning, 3D printing, vacuum filtration, spray drying and emulsion methods are highlighted. In addition, the physio-chemical properties of these macrostructures are discussed with the relationship among the porosity, surface area and the bulk density. The perspective also highlights the versatile potentials of different 3DMs in wastewater remediation by adsorption, desalination, and catalytic oxidation, etc. Following the concluding remarks, future outlooks on commercial applications of 3DMs are also provided.

Optimization of the cutter size and tool orientation for reaching the critical state with multi-constraints in deep and narrow channel parts machining

Increasing the cutter size to enhance its stiffness is of great significance for improving the machining efficiency and precision of deep and narrow channel parts. In this paper, the concept of cutter size critical sphere (CSCS) is presented, which is a specified sphere and tangent to several geometric constraints of tool accessible regions. With this concept, the complex multi-constraints of the workpiece can be transformed into several simple but precise geometric conditions to optimize the size and tool orientation of a conical cutter. The conical cutter generated by CSCS can reach a critical state with multi-constraints simultaneously. Firstly, the mathematical principle of the conical cutter generated by a cylindrical cutter is deduced based on the motion envelope theory. Secondly, the concept of CSCS is proposed based on the deduced mathematical principle and the calculation method of the CSCS with the general situation is provided. Thirdly, the CSCS with special situations is discussed and the calculation method is proposed. Fourthly, the mathematical model and solving algorithm for the max-size CSCS is given. The solving algorithm is designed based on the 3D Medial Axis Transformation (3D MAT) theory. Finally, the proposed method is verified by three simulation experiments and a comparison experiment. The results show that the proposed method can efficiently and accurately calculate the max size and tool orientation of the conical cutter simultaneously. The optimized conical cutter can be tangent to the multi-constraints of the workpiece but do no interfer with them.

Modeling the density gradient of 3D nanofiber scaffolds fabricated by divergence electrospinning

Following recent insights on structure-cell-function interactions and the critical role of the extracellular matrix (ECM), the latest biofabrication approaches have increasingly focused on designing materials with biomimetic microarchitecture. Divergence electrospinning is a novel fabrication method for three-dimensional (3D) nanofiber scaffolds. It is introduced to produce 3D nanofiber mats that have numerous applications in regenerative medicine and tissue engineering. One of the most important characteristics of 3D nanofiber mats is the density gradient. This study provides a statistical analysis and response surface modeling framework based on experimental data to evaluate the manner by which the geometric designs of double-bevel collectors influence the fiber density gradient. Specifically, variance of analysis and sensitivity analysis were performed to identify parameters that had significant effects, and a response surface model embedded with seven location indicators was developed to predict the spatial distribution of fiber density for different collector designs. It was concluded that the collector height, bevel angle, and their interactions were significant factors influencing the density gradient. This study revealed the sensitivity of system configuration and provided an optimization tool for process controllability of microstructure gradients.

Synthesis of Sandwich-Like Nanostructure Fillers and Their Use in Different Types of Thermal Composites.

Thermally conductive yet electrically insulating two-dimensional boron nitride nanosheets (BNNSs) have been an ideal choice for the enhanced fillers for improving thermal properties of polymer-based composites. As a nanofiller with an ultrahigh aspect ratio, BNNSs result in conspicuous stacking along the planar direction in the preparation of composites, which results in strong anisotropy of heat transfer and suppresses out-plane thermal dissipation. Thus, it is necessary to facilitate the out-plane heat transfer by building a favorable microstructure. Focusing on the structural design of the nanofiller itself here, we have fabricated a novel three-dimensional nanofiller with improved out-plane connections. Carbon nanotubes (CNTs) have been grown in situ on the surface of BNNSs using chemical vapor deposition. Utilizing these sandwich-like nanostructure BNNSs/CNTs as fillers in the composites, we have assembled diverse sorts of composites, such as flexible films, scleroid 3D mats, painted ink, and viscous grease. Simultaneously, their thermal and insulating properties have been evaluated. A nearly 330% enhancement of out-plane thermal conductivity from the control sample filled with pristine BNNS is achieved, and the composite also exhibits good electrical resistivity of above 7.5 × 1010 Ω mm. The results indicate that the BNNS/CNT filler has superior thermal performance over the original BNNS while maintaining a satisfactory electrical resistivity to avoid short-circuits in high-power electronics. Furthermore, the prepared grease used as a thermal interface material shows impressive heat dissipation performance when applied on a running computer.

Wearable high-performance pressure sensors based on three-dimensional electrospun conductive nanofibers

Polymer-based pressure sensors play a key role in realizing lightweight and inexpensive wearable devices for healthcare and environmental monitoring systems. Here, conductive core/shell polymer nanofibers composed of poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP)/poly(3,4-ethylenedioxythiophene) (PEDOT) are fabricated using three-dimensional (3D) electrospinning and vapor deposition polymerization methods, and the resulting sponge-like 3D membranes are used to create piezoresistive-type pressure sensors. Interestingly, the PEDOT shell consists of well-dispersed spherical bumps, leading to the formation of a hierarchical conductive surface that enhances the sensitivity to external pressure. The sponge-like 3D mats exhibit a much higher pressure sensitivity than the conventional electrospun 2D mats due to their enhanced porosity and pressure-tunable contact area. Furthermore, large-area, wireless, 16 × 10 multiarray pressure sensors for the spatiotemporal mapping of multiple pressure points and wearable bands for monitoring blood pressure have been fabricated from these 3D mats. To the best of our knowledge, this is the first report of the fabrication of electrospun 3D membranes with nanoscopically engineered fibers that can detect changes in external pressure with high sensitivity. The developed method opens a new route to the mass production of polymer-based pressure sensors with high mechanical durability, which creates additional possibilities for the development of human–machine interfaces.

Designing superhydrophobic disordered arrays of fibers with hierarchical roughness and low-surface-energy

Hierarchical roughness and low surface energy are the main criteria for designing superhydrophobic surfaces with extreme water repellency. Herein, we present a step-wise approach to devise three-dimensional (3D) superhydrophobic disordered arrays of fibers in the form of nonwoven mats exhibiting hierarchical surface roughness and low surface energy. Key design parameters in the form of roughness factors at multiple length scales for 3D nonwoven mats have been quantified. The contact angles have been predicted for each of the wetting regimes that exists for nonwoven mats with predefined level of hierarchical surface roughness and surface energy. Experimental realization of superhydrophobic mats was attained by decorating the highly hydrophilic nonwoven viscose fibers with ZnO rods that effectively modulated the surface roughness at multiple length scales and subsequently, the surface energy was lowered using fluorocarbon treatment. Synergistic effects of hierarchical roughness and surface energy have systematically increased the static water contact angle of nonwoven mat (up to 164°) and simultaneously, lowered the roll-off angle (≈11°).

Formation of three-dimensionality in polyaniline-based nanofibers: A highly conductive permeable scaffold for stem cells residence

ABSTRACTA highly conductive and three-dimensional electrospun scaffold with proper cell intrusion was developed by virtue of the electrical conductivity of the electrospinning solution. In polyaniline (PANi)/poly (ϵ-caprolactone) (PCL) blend, the weight ratio of PANi to PCL was increased to raise solution conductivity. The electrospun fibers were characterized by microscopy, conductivity and cell culture study. Once ratio of PANi increased from 7% to 70%, the fibers changed from a flat two-dimensional into a three-dimensional structure, and their electrical conductivity increased 1,000 times. Moreover, the cell accessibility of 3D mat greatly overcame that of the 2D mat.

Testing of 3-Dimensional Stabilizing Elements for Protection of Slopes: Possibilities of <i>In Situ</i> Testing

The testing results obtained during investigation of 3D mat are presented in the article. The spatial mat is designed to provide a cheap, efficient and durable soil stabilization on slopes. The testing was focused on development of suitable methods to be used when assessing foil properties on-site. The tested samples were extracted from mats that were used for soil stabilization at the location of mine Nástup Tušimice (Company Severočeské doly, Czech Republic) and exposed to external environment and weathering for 2 years. The performance of the mats was compared with reference samples from unused mats stored for 2 years in laboratory conditions. The testing revealed that deterioration of the material is negligible over the period of 2 years.

Solution blowing of chitosan/PLA/PEG hydrogel nanofibers for wound dressing

In this study, a kind of hydrogel nanofibers were successfully fabricated via solution blowing of chitosan (CS) and polylactic acid (PLA) solutions mixed with various contents of polyethylene glycol (PEG) to offer hydration. The nanofibers with PEG content varying were average 341-376 nm in diameter with smooth surface and distributed randomly forming three-dimension (3D) mats. Glutaraldehyde (GA) vapor was then applied to impart stability, and the cross-linking reaction mainly occurred between GA and hydroxyl groups which was confirmed by XPS. The hydrogel nanofibers showed quick absorption behavior, high equilibrate water absorption and good air permeability which could help the mats absorbing excess exudates, creating a moist wound healing environment and oxygen exchanging in wound healing. The mats also exhibited good antibacterial activities against E. coil. The combination advantages of nanofibers mats and hydrogel will help it find promising application in wound healing.

Fabrication of a Low Density Carbon Fiber Foam and Its Characterization as a Strain Gauge.

Samples of carbon nano-fiber foam (CFF), essentially a 3D solid mat of intertwined nanofibers of pure carbon, were grown using the Constrained Formation of Fibrous Nanostructures (CoFFiN) process in a steel mold at 550 °C from a palladium particle catalysts exposed to fuel rich mixtures of ethylene and oxygen. The resulting material was studied using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), Surface area analysis (BET), and Thermogravimetric Analysis (TGA). Transient and dynamic mechanical tests clearly demonstrated that the material is viscoelastic. Concomitant mechanical and electrical testing of samples revealed the material to have electrical properties appropriate for application as the sensing element of a strain gauge. The sample resistance versus strain values stabilize after a few compression cycles to show a perfectly linear relationship. Study of microstructure, mechanical and electrical properties of the low density samples confirm the uniqueness of the material: It is formed entirely of independent fibers of diverse diameters that interlock forming a tridimensional body that can be grown into different shapes and sizes at moderate temperatures. It regains its shape after loads are removed, is light weight, presents viscoelastic behavior, thermal stability up to 550 °C, hydrophobicity, and is electrically conductive.

Ultra high-yield one-step synthesis of conductive and superhydrophobic three-dimensional mats of carbon nanofibers via full catalysis of unconstrained thin films

We directly synthesized large conductive and superhydrophobic 3D mats of entangled carbon nanofibers (CNFs). The mechanism is based on thin film delamination and bi-directional catalytic CNF growth.

LiCoPO4—3D carbon nanofiber composites as possible cathode materials for high voltage applications

Electrospun and carbonized 3D nanofiber mats coated with olivine structured lithium cobalt phosphate (LiCoPO4) were formed by a Pechini-assisted sol–gel process as cathode material for lithium ion batteries. 3D nonwoven nanofibers were soaked in aqueous solution containing lithium, cobalt salts and phosphates at 80°C for 2h. Then, the composites were dried and annealed at 730°C for 2 to 12h in nitrogen atmosphere. Crystalline deposits were uniformly distributed on the carbon nanofiber surface. The “loading” of the cathode material on the 3D carbon nanofiber composites reached 300wt%. The electrochemical measurements revealed the discharge specific capacity (measured at a discharge rate of 0.1C and room temperature) reaching a maximum value of 46mAhg−1 after annealing time t=5h.

Design of a 3D aligned myocardial tissue construct from biodegradable polyesters

The heart does not regenerate new functional tissue when myocardium dies following coronary artery occlusion, or if it is defective. Ventricular restoration involves excising the infarct and replacing it with a cardiac patch to restore the heart to a more healthy condition. The goal of this study was to design and develop a clinically applicable myocardial patch to replace myocardial infarcts and improve long-term heart function. A basic design composed of 3D microfibrous mats that house mesenchymal stem cells (MSCs) was developed from human umbilical cord matrix (Wharton's Jelly) cells aligned in parallel to each other mimicking the native myocardium. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(L-D,L-lactic acid) (P(L-D,L)LA) and poly(glycerol sebacate) (PGS) were blended and electrospun into aligned fiber mats with fiber diameter ranging between 1.10 and 1.25 microm. The micron-sized parallel fibers of the polymer blend were effective in cell alignment and cells have penetrated deep within the mat through the fiber interstices, occupying the whole structure; 8-9 cell layers were obtained. Biodegradable macroporous tubings were introduced to serve as nutrient delivery route. It was possible to create a thick myocardial patch with structure similar to the native tissue and with a capability to grow.