2D Mats Research Articles

Gas foamed scaffolds as smart 3D structures in skin tissue engineering

Globally, wound care is a major problem that poses big issues for national healthcare systems. Consequently, the development of wound dressings, systems applied over a wound to prevent complications and speed up recovery, is receiving increasing attention. Electrospun nanofibrous scaffolds gained great interest in the medical field due to their many advantages and beneficial characteristics. However, they are formed by of densely packed fiber layers, which render the available space between adjacent fibers minimal. In this study, nanometric fibers from pullulan polymeric blends were developed using cricket powder as novel component, due to its high chitin and chitosan content. Hydroxyapatite was also added due to its biocompatibility and capability to interact with the host tissues. The 2D mats based on electropsun fibers in membrane were converted to a 3D structure by gas foaming, involving NaBH4. The obtained 3D systems were characterized for their morphology and composition, and mechanical properties. The scaffolds biocompatibility was tested on normal human dermal fibroblasts and mesenchymal stem cells, and cell adhesion was assessed. TNF-α secretion was thereafter characterized to evaluate the anti-inflammatory effects of the scaffolds on macrophages, and their antioxidant activity was also investigated. Finally, an evaluation of the scaffolds’ safety and efficacy in vivo on a murine incisional and burn model was performed. The results obtained not only revealed greater structural and mechanical integrity of the gas-foamed scaffolds containing cricket powder, but also higher cytocompatibility towards different cell lines together with anti-inflammatory and antioxidant properties, thereby making them innovative tools to improve the process of wound healing.

Transforming layered 2D mats into multiphasic 3D nanofiber scaffolds with tailored gradient features for tissue regeneration.

Multiphasic scaffolds with tailored gradient features hold significant promise for tissue regeneration applications. Herein, this work reports the transformation of two-dimensional (2D) layered fiber mats into three dimensional (3D) multiphasic scaffolds using a 'solids-of-revolution' inspired gas-foaming expansion technology. These scaffolds feature precise control over fiber alignment, pore size, and regional structure. Manipulating nanofiber mat layers and Pluronic F127 concentrations allows further customization of pore size and fiber alignment within different scaffold regions. The cellular response to multiphasic scaffolds demonstrates the number of cells migrated and proliferated onto the scaffolds are mainly dependent on the pore size rather than fiber alignment. In vivo subcutaneous implantation of multiphasic scaffolds to rats reveals substantial cell infiltration, neo tissue formation, collagen deposition, and new vessel formation within scaffolds, greatly surpassing the capabilities of traditional nanofiber mats. Histological examination indicates the importance of optimizing pore size and fiber alignment for promotion of cell infiltration and tissue regeneration. Overall, these scaffolds have potential applications in tissue modeling, studying tissue-tissue interactions, interface tissue engineering, and high-throughput screening for optimized tissue regeneration.

Unveiling the Mechanism of the in Situ Formation of 3D Fiber Macroassemblies with Controlled Properties.

Electrospinning technique is well-known for the generation of different fibers. While it is a "simple" technique, it lies in the fact that the fibers are typically produced in the form of densely packed two-dimensional (2D) mats with limited thickness, shape, and porosity. The highly demanded three-dimensional (3D) fiber assemblies have been explored by time-consuming postprocessing and/or complex setup modifications. Here, we use a classic electrospinning setup to directly produce 3D fiber macrostructures only by modulating the spinning solution. Increasing solution conductivity modifies electrodynamic jet behavior and fiber assembling process; both are observed in situ using a high-speed camera. More viscous solutions render thicker fibers that own enhanced mechanical stiffness as examined by finite element analysis. We reveal the correlation between the universal solution parameters and the dimensionality of fiber assemblies, thereof, enlightening the design of more "3D spinnable" solutions that are compatible with any commercial electrospinning equipment. After a calcination step, ultralightweight ceramic fiber assemblies are generated. These inexpensive materials can clean up exceptionally large fractions of oil spillages and provide high-performance thermal insulation. This work would drive the development and scale-up production of next-generation 3D fiber materials for engineering, biomedical, and environmental applications.

Amplified piezoelectric response with β-phase formation in PVDF blended 3D cotton type nanofibers for osteogenic differentiation

PVDF (Polyvinylidene Fluoride) is a representative piezoelectric polymer, and many studies are being conducted to increase the β-phase, a polar chain structure that exhibits piezoelectricity. Electrospinning is known as an effective method to increase the β-phase of PVDF, and electrospun PVDF fibers are attractive materials that can be widely used in various fields due to their flexibility and high biocompatibility. However, since electrospun fibers are generally manufactured as 2D mats, it is difficult to use them as actual tissue scaffolds. In this study, PVDF was fabricated in 3D form by controlling the relative humidity (RH) during the electrospinning process. When the RH was set high during the electrospinning process, the fibers were manufactured in a cotton-like form. In addition, various post-treatment processes were performed to increase the β-phase, and the analysis showed that the post-treatment was effective in improving the β-phase of PVDF. The 3D cotton-type fibers performed in vitro cell culture experiments using MC3T3-E1 cells, confirming the possibility that they could be applied to tissue regeneration fields such as bone regeneration as scaffolds in the future. The manufactured 3D cotton-type PVDF fiber is expected to be applied not only to bio-scaffold but also to various fields requiring piezoelectricity.

Fabrication of nanocomposite/nanofibrous functionally graded biomimetic scaffolds for osteochondral tissue regeneration

One of the main challenges in treating osteochondral lesions via tissue engineering approach is providing scaffolds with unique characteristics to mimic the complexity. It has led to application of heterogeneous scaffolds as a potential candidate for engineering of osteochondral tissues, in which graded multilayered-structure should promote bone and cartilage growth. By designing three-dimensional (3D)-nanofibrous scaffolds mimicking the native extracellular matrix's nanoscale structure, cells can grow in controlled conditions and regenerate the damaged tissue. In this study, novel 3D-functionality graded nanofibrous scaffolds composed of five layers based on different compositions containing polycaprolactone(PCL)/gelatin(Gel)/nanohydroxyapatite (nHA) for osteoregeneration and chitosan(Cs)/polyvinylalcohol(PVA) for chondral regeneration are introduced. This scaffold is fabricated by electrospinning technique using spring as collector to create 3D-nanofibrous scaffolds. Fourier-transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, mechanical compression test, porosimetry, and water uptake studies were applied to study each layer's physicochemical properties and whole functionally graded scaffold. Besides, biodegradation and biological studies were done to investigate biological performance of scaffold. Results showed that each layer has a fibrous structure with continuous nanofibers with improved pore size and porosity of novel 3D scaffold (6-13 μm and 90%) compared with two-dimensional (2D) mat (2.2 μm and 19.3%) with higher water uptake capacity (about 100 times of 2D mat). Compression modulus of electrospun scaffold was increased to 78 MPa by adding nHA. The biological studies revealed that the layer designed for osteoregeneration could improve cell proliferation rate in comparison to the layer designed for chondral regeneration. These results showed such structure possesses a promising potential for the treatment of osteochondral defects.

Three-dimensional porous carbonaceous network with in-situ entrapped metallic cobalt for supercapacitor application

Herein, we outline the fabrication of highly porous three-dimensional carbon-fiber network anchored with uniform metallic cobalt (Co) via electrospinning and subsequent post-modification approaches. First, cobalt acetate solution saturated electrospun polyacrylonitrile (PAN) nanofibrous mat was subjected to sodium borohydride (NaBH4) solution which results in the fabrication of three dimensional (3D) hierarchical multilayer network. Restructuring of the 2D mat into multilayered sponges with metal particles entrapment is attributed to the in-situ generated hydrogen gas into the interconnected pores of the fibrous network simultaneous with reduction of cobalt salt into metallic cobalt by NaBH4. The resulting mesh was stabilized and carbonization at inert atmosphere to obtain metallic cobalt (Co) embedded 3D carbon nanofibrous networks (Co@3D-CNFs). Physicochemical characterization and electrochemical analysis were performed. Results show carbon network was found to be expanded with bubbling like structures often embedded metallic Co nanoparticles. X-ray diffraction (XRD) pattern confirms the existence of the metallic cobalt particles on the carbon fiber networks. Furthermore, we establish a resulting composite (Co@3D-CNFs) identify the enhanced electrochemical performance having specific capacitance 762 F g−1 compared to 173 and 180 F g−1 for corresponding @3D-CNFs and 2D carbon nanofiber network with cobalt doped (Co@2D-CNFs) counterparts, respectively. The assembled Co2@3D-CNFs//NGH ASC device exhibits a high energy density 24.6 W h Kg−1 at 797 W kg−1 power density with an operating voltage of 1.6 V (vs Ag/AgCl). The device further shows good capacitance retention (90.1%) after 5000 cycles. This research shows the simple and cost-effective strategy to make metallic particles embedded 3D porous carbonaceous electrode materials which can have great potential for energy storage application.

Novel porous three-dimensional nanofibrous scaffolds for accelerating wound healing

Too small pore size of electrospinning wound dressings limits cells of adjacent tissue to grow into the wound. Herein, a new aqueous phase fiber reassembly technology was addressed to fabricate polycaprolactone-polyethylene glycol-polycaprolactone (PCL-PEG-PCL) 3D nanofibrous scaffolds (TNSs) as a promising candidate for accelerating wound healing. The TNSs showed larger pore size with higher porosity compared with PCL-PEG-PCL 2D mats. The micron-sized hierarchical porous structure of TNSs enhanced water storage capacity, resulting in excellent water absorption. In addition, likely due to the rough surface and loose pore structure, the TNSs could effectively enhance L929 cell adhesion, proliferation and migration behaviors compared to that of 2D mats. Finally, in vivo tests supported the results of cellular experiments, TNSs could significantly promote the wound healing compared with 2D mats.

Three-dimensional nanofiber scaffolds are superior to two-dimensional mats in micro-oriented extraction of chlorobenzenes.

Three-dimensional (3D) polyamide scaffolds were fabricated by applying a solvent bath as the collecting element. Electrospun nanofibers were immersed into the solvent bath to give a material with a laminated 3D texture. In parallel, 2D nanofibers were synthesized and utilized as microextractive phases in a needle trap device to compare the capabilities of 2D and 3D materials in terms of headspace extraction of various chlorobenzenes (chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene and 1,2,3,4-tetrachlorobenzene). The results demonstrate the superiority of 3D nanofibrous scaffolds over 2D mats. The porosity, morphology, and thermal stability of the 3D scaffolds were characterized using FT-IR, scanning electron microscopy, confocal laser scanning microscopy and thermogravimetric analysis. The CLSM images were reconstructed and analyzed by Image J software, and eventually the enhancement of porosity using 3D scaffolds was confirmed. The type of solvent bath, polyamide solution concentration and other parameters were optimized. Following thermal desorption of the chlorobenzenes, they were quantified by GC-MS. Under optimum conditions, the calibration plots cover the 0.004-1.0pgμL-1 concentration range and the limits of detection are in the range from 0.8-3pgmL-1. The relative standard deviations (RSDs) are between 3 and 8% and 3-10% (n= 3) at spiking levels of 200 and 1000ngL-1, respectively. The RSDs for the needle-to-needle repeatability are <15% (for n= 3). This needle trap microextraction method was applied to the analysis of river water, sea water, and of inlet water of a water treatment plant. Graphical abstract Schematic diagram symbolizing the extractive effectiveness of sponge-like 3D nanofibrous scaffolds with respect to smooth 2D electrospun nanofibers. Under the same experimental conditions, higher porosity of 3D scaffolds is amazingly contributed to the more accessible adsorptive sites which in turn makes them drastic and innovative candidate for micro-oriented extraction purposes.

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.

Ion beam modification of two-dimensional materials: Characterization, properties, and applications

The layered two-dimensional (2D) materials, e.g., the well-known graphene, transition metal dichalcogenides, and topological insulators, have attracted great interest of researchers from fundamental research as well as industries owing to their intriguing properties in a number of aspects. In practical applications, the efficient modification of the features of 2D materials is compelling and essential to achieve desired functionalities. Ion implantation has been successfully applied to synthesize graphene. The most exotic advantage of ion beam technology is that it offers distinct options of energetic beams, which has recently shown the unique capability to modify and tailor the properties of versatile 2D materials. To name a few, the energetic ion beams could implement the surface morphology or layer-to-layer structural engineering of 2D materials. At the microcosmic level, the introduction of ion beam induced defects and intentional doping of specific ions are the basis of tailoring properties of 2D mat...

Novel 3D scaffold with enhanced physical and cell response properties for bone tissue regeneration, fabricated by patterned electrospinning/electrospraying.

Developing three dimensional scaffolds mimicking the nanoscale structure of native extracellular matrix is a key parameter in tissue regeneration. In this study, we aimed to introduce a novel 3D structures composed of nanofibers (NF) and micro particles (MP) and compare their efficiency with 2D nanofibrous scaffold. The conventional nanofibrous PCL scaffolds are 2D mats fabricated by the electrospinning technique, whereas the NF/MP and patterned NF/MP PCL scaffolds are three dimensional structures fabricated by a modified electrospinning/electrospraying technique. The mentioned method was carried out by varying the electrospinning solution parameters and use of a metal mesh as the collector. Detailed fabrication process and morphological properties of the fabricated structures is discussed and porosity, pore size and PBS solution absorption value of the prepared structures are reported. Compared with the 2D structure, 3D scaffolds possessed enhanced porosity and pore size which led to the significant increase in their water uptake capacity. In vitro cell experiments were carried out on the prepared structures by the use of MG-63 osteosarcoma cell line. The fabricated 3D structures offered significantly increased cell attachment, spread and diffusion which were confirmed by SEM analysis. In vitro cytocompatibility assessed by MTT colorimetric assay indicated a continuous cell proliferation over 21days on the innovative 3D structure, while on 2D mat cell proliferation stopped at early time points. Enhanced osteogenic differentiation of the seeded MG-63 cells on 3D scaffold was confirmed by the remarkable ALP activity together with increased and accelerated calcium deposition on this structure compared to 2D mat. Massive and well distributed bone minerals formed on patterned 3D structure were shown by EDX analysis. In comparison between NF/MP quasi-3D and Patterned NF/MP 3D scaffolds, patterned structures proceeded in all of the above properties. As such, the innovative Patterned NF/MP 3D scaffold could be considered as a proper bone graft substitute for bone tissue regeneration.

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.

Advanced micro- and nanofabrication technologies for tissue engineering

The ability of the living body to heal and regenerate itself following trauma is astonishing. Numerous events of repair and regeneration occur during our lifetime, most of which we are never aware of. Unfortunately, in some cases, the injury or defect cannot be adequately repaired solely by nature and medical intervention is required.

Fabrication of a three-dimensional nanofibrous scaffold with lattice pores using direct-write electrospinning

Nanofibrous structures afford valuable functionality and performance to scaffolds in tissue engineering. As a result, electrospun nanofibers have been used as scaffold materials in various tissue regeneration techniques. However, their application to scaffolds has been limited to two-dimensional (2D) mats because of the difficulty in generating regular pores with interconnectivity, which is a critical parameter in three-dimensional (3D) scaffolds. In this study, we demonstrated a 3D nanofibrous scaffold with regular pores fabricated using a direct-write electrospinning nanofibrous pattern mat followed by stacking of the mats into a 3D structure. The fabricated 3D scaffold could be successfully used for 3D soft-tissue regeneration with significantly improved cell migration into the scaffold.

Effects of microstructure on flow properties of fibrous porous media at moderate Reynolds number

In this study, effects of microstructure on the viscous permeability and Forchheimer coefficient of monodispersed fibers are investigated. The porous material is represented by a unit cell which is assumed to be repeated throughout the medium. Based on the orientation of the fibers in the space, fibrous media are divided into three categories: one-, two-, and three-directional (1D, 2D, and 3D) structures. Parallel and transverse flow through square arrangements of 1D fibers, simple 2D mats, and 3D simple cubic structures are solved numerically over a wide range of porosity (0.35 < ε < 0.95) and Reynolds number (0.01 < Re < 200). The results are used to calculate the permeability and the inertial coefficient of the considered geometries. An experimental study is performed; the flow coefficients of three different ordered tube banks in the moderate range of Reynolds number (0.001 < Re < 15) are determined. The numerical results are successfully compared with the present and the existing experimental data in the literature. The results suggest that the permeability and Forchheimer coefficient are functions of porosity and fiber orientation. A comparison of the experimental and numerical results with the Ergun equation reveals that this equation is not suitable for highly porous materials. As such, accurate correlations are proposed for determining the Forchheimer coefficient in fibrous porous media.

Multi-Walled Carbon Nanotube Based Sensors for Selective Detection of Chemical Pollutants&lt;sup&gt;&lt;/sup&gt;

This work reports the design of a resistive gas sensor based on 2D mats of multi-walled carbon nanotubes (MWCNT). The sensor sensitivity was optimised using chlorine by tuning both MWCNT network morphology and MWCNT electronic properties. Raw CNT were compared with annealed CNT. Besides, with the aim to enhance the sensor sensitivity and selectivity for detection of several gases, MWCNT were functionalized with poly (phenylene)-like or vinyl polymers using a process based on the diazonium chemistry. In this paper, we will mention the preparation of such sensors and we will demonstrate that the optimized devices are operating at room temperature, for the detection of pollutants such as chlorine, hydrogen chloride and ammonia. Such sensors are able to detect down to 30 ppb of pollutant, in particular for chlorine.

Engineering the Unique 2D Mat of Graphene to Achieve Graphene-TiO2 Nanocomposite for Photocatalytic Selective Transformation: What Advantage does Graphene Have over Its Forebear Carbon Nanotube?

Increasing interest has been devoted to synthesizing graphene (GR)-semiconductor nanocomposites as photocatalysts for potential applications, which is very similar to its forebear carbon nanotube (CNT)-semiconductor photocatalysts. Unfortunately, a thoughtful and inevitable comparison between GR- and CNT-semiconductors as photocatalysts is often neglected in literature. This situation may give incomplete or exaggerated information on the contribution role of GR to enhance the semiconductor photocatalytic activity, as compared to CNT. Thus, our knowledge regarding the specific advantage of GR over CNT on how to design more efficient GR-semiconductor nanocomposites and understanding the origin of their enhanced photocatalytic performance is far from satisfactory. By taking the TiO(2) semiconductor as an example, we conceptually demonstrate how to synthesize a more efficient GR-TiO(2) nanocomposite as a visible light photocatalyst toward selective oxidation of alcohols under mild conditions. Comparison between GR-TiO(2) and CNT-TiO(2) discloses the prominent advantage of GR over CNT on both controlling the morphology of GR-TiO(2) nanocomposite and enhancing the photocatalytic activity of TiO(2). This work clearly highlights the importance and necessity for a comparison investigation between GR- and CNT-semiconductors as photocatalysts, which will promote our in-depth fundamental understanding on the analogy and difference between GR and CNT on controlling the morphology of GR (or CNT)-semiconductor nanocomposites and enhancing the photocatalytic performance. Therefore, we appeal the photocatalysis community to pay attention to this respect rather than separately imposing hype on the miracle of GR in much the same way as its carbon forebears, which could significantly advance our rational fabrication of smart GR-semiconductor nanocomposites for artificial photosynthesis.

Optimized network of multi-walled carbon nanotubes for chemical sensing

This work reports the design of a resistive gas sensor based on 2D mats of multi-walled carbonnanotubes (MWCNTs) grown by aerosol-assisted chemical vapour deposition. The sensorsensitivity was optimized using chlorine as analyte by tuning both CNT network morphologyand CNT electronic properties. Optimized devices, operating at room temperature, havebeen calibrated over a large range of concentration and are shown to be sensitive down to27 ppb of chlorine. The as-grown MWCNT response is compared with responses of2000 °C annealed CNTs, as well as of nitrogen-doped CNTs and CNTs functionalized withpolyethyleneimine (PEI). Under chlorine exposure, the resistance decrease ofas-grown and annealed CNTs is attributed to charge transfer from chlorine toCNTs and demonstrates their p-type semiconductor behaviour. XPS analysis ofCNTs exposed to chlorine shows the presence of chloride species that confirmselectron charge transfer from chlorine to CNTs. By contrast, the resistance ofnitrogen-doped and PEI functionalized CNTs exposed to chlorine increases, inagreement with their n-type semiconductor nature. The best response is obtainedusing annealed CNTs and is attributed to their higher degree of crystallinity.

Physicochemical characterisation of degrading polycaprolactone scaffolds

A degradation study investigating the hydrolysis of different scaffolds of polycaprolactone suspended in phosphate buffer solution at 37 °C was performed over a three month period. Structures included electrospun fibres, held as 2D mats and 3D bundles, and solvent cast films. These structures and their surrounding solutions were physiochemically characterised using a range of techniques. Changes in scaffold physicochemical properties were observed over the course of the study, including significant loss in molecular mass, increases in thermal properties and crystallinity, and increases in tensile properties. The presence of degradation products, such as capronic acid containing compounds was also identified in the surrounding solution. 3D electrospun bundles - as a consequence of being the least crystalline scaffold and hence most susceptible to hydrolysis – demonstrated greatest reduction in molecular mass over the three months, followed by 2D electrospun mats, and the lowest mass loss was observed for solvent cast films.

Generating the Mid-Surface of a Solid using 2D MAT of its Faces

Computer-Aided Design and Applications is an international journal on the applications of CAD and CAM. It publishes papers in the general domain of CAD plus in emerging fields like bio-CAD, nano-CAD, soft-CAD, garment-CAD, PLM, PDM, CAD data mining, CAD and the internet, CAD education, genetic algorithms and CAD engines. The journal is aimed at all developers and users of CAD technology to ptovide CAD solutions for various stages of design and manufacturing. The journal publishes all about Computer-Aided Design and Computer-Aided technologies.