Fabrication Route Research Articles

Design and fabrication of a vanadium dioxide-based actively switchable wire grid polarizer for near-infrared applications

This study introduces an actively switchable wire grid polarizer exploiting the semiconductor-metal transition of vanadium dioxide. Operating at a near-infrared wavelength, the device features a SiO2 substrate with VO2 deposited by atomic layer deposition. We demonstrate the design using rigorous coupled wave analysis and show a viable fabrication route. Polarisation-resolved spectral transmission measurements show switching of the extinction ratio from 37.5 (on-state) to 1.6 (off-state). Despite observed deviations between measured and theoretical transmission values, the device shows potential in miniaturized imaging processes, polarization measurements, and ellipsometry.

A Comprehensive Review on Barium Titanate Nanoparticles as a Persuasive Piezoelectric Material for Biomedical Applications: Prospects and Challenges.

Stimulation of cells with electrical cues is an imperative approach to interact with biological systems and has been exploited in clinical practices over a wide range of pathological ailments. This bioelectric interface has been extensively explored with the help of piezoelectric materials, leading to remarkable advancement in the past twodecades. Among other members of this fraternity, colloidal perovskite barium titanate (BaTiO3 ) has gained substantial interest due to its noteworthy properties which includes high dielectric constant and excellent ferroelectric properties along with acceptable biocompatibility. Significant progression is witnessed for BaTiO3 nanoparticles (BaTiO3 NPs) as potent candidates for biomedical applications and in wearable bioelectronics, making them a promising personal healthcare platform. The current review highlights the nanostructured piezoelectric bio interface of BaTiO3 NPs in applications comprising drug delivery, tissue engineering, bioimaging, bioelectronics, and wearable devices. Particular attention has been dedicated toward the fabrication routes of BaTiO3 NPs along with different approaches for its surface modifications. This review offers a comprehensive discussion on the utility of BaTiO3 NPs as active devices rather than passive structural unit behaving as carriers for biomolecules. The employment of BaTiO3 NPs presents new scenarios and opportunity in the vast field of nanomedicines for biomedical applications.

Finite Element Analysis of Different Infill Patterns for 3D Printed Tidal Turbine Blade

The fabrication route for tidal turbine blades has been compounded with the appearance of additive manufacturing; with the use of infill patterns, improvement of mechanical strength and material reduction for 3D printed parts can be obtained. Through finite element analysis and three-point bend tests, the optimal infill lattice pattern, and the viability of the shell–infill turbine blade model as an alternative to the conventional shell-spar model was determined. Out of a selection of infills, the best infill pattern was determined as the hexagonal infill pattern oriented in-plane. A representative volume element was modeled in ANSYS Material Designer, resulting in the homogenized properties of the in-plane hexagonal lattice. After validation, the homogenized properties were applied to the tidal turbine blade. The shell–infill model was based on the volume of the final shell-spar model which had a blade deflection of 9.720% of the blade length. The difference in the deflection between the homogenized infill and the spar cross-section was 0.00125% with a maximum stress of 170.3 MPa which was within the tensile strength and flexure strength of the carbon fiber with onyx base material. Conclusively, the homogenized infill was determined as a suitable alternative to the spar cross-section. The best orientation of the infill relative to the horizontal orientation of the blade was 0 degrees; however, the lack of trend made it inconclusive whether 0 degrees was the absolute optimal infill orientation.

Large-area opposing double nanocrescents-nanoparticle arrays for polarization dependent SERS effects

An efficient fabrication route is developed to produce a large-area and highly-ordered Ag opposing double nanocrescents-nanoparticle (AODCP) array by combining the ultra-thin alumina membrane (UTAM) mask, annealing and angle deposition techniques. This strategy exhibits a controllable fabrication process of crescent-shaped plasmonic nanostructures wherein the number and orientation of the nanocrescents can be independently tuned. The localized electrical fields are extremely enhanced in the nanogaps and at the tips of the nanocrescents due to the coupling between the nanocrescents and nanoparticles, and their distributions depend on the polarization of the incident light, which are confirmed by numerical simulations. Polarization-dependent surface enhanced Raman scattering (SERS) is experimentally demonstrated on this AODCP substrate with remarkable sensitivity and reproducibility. The results suggest the proposed AODCP arrays are promising for the applications in the fields of nonlinear optics, optical sensors and surface enhanced spectroscopy.

Enhancing the Mechanical Performance of Fiber‐Reinforced Polymer Composites Using Carbon Nanotubes as an Effective Nano‐Phase Reinforcement

AbstractCarbon nanotubes (CNTs) are an economical and multi‐functional nanofiller that can further elevate the versatile performance of fiber‐reinforced polymer (FRP). The past two decades have seen significant progress in the design, fabrication, and characterization of CNTs modified FRPs (CNT‐FRPs). The introduction of CNTs has been proven to enhance the key mechanical properties of CNT‐FRPs and endow the composite with additional functional properties. In this review, the fabrication routes of CNT incorporation into FRPs are first discussed, and then the critical effects of CNTs on various mechanical properties of CNT‐FRPs are described. Next, as a complement to the experimental results, modeling studies on CNT‐FRPs are included to reveal the underlying structural effects, followed by a discussion on the reinforcement and toughening mechanisms of CNT‐FRPs. The intent of this review is to provide a comprehensive summary on CNT modified FRP composites, and to shed light on the future research and development of CNT modified composites.

Nano sponge like metal-based coating with self-regenerative superhydrophobicity using simple flame spraying

In present investigation, a low-cost and facile fabrication route for developing nano-sponge like aluminum coating on carbon steel through flame spraying is demonstrated. The silanization of coating resulted in highly de-wetting state with contact angle >152°, low contact angle hysteresis and sliding angle (<5°). The coating also showed low adhesion force of 6 µN with water. The superhydrophobic coating showed 56 times lower corrosion rate than carbon steel due to high polarization resistance. The coating showed self-regenerative nature during abrasion resulting in persistent superhydrophobicity. High durability was also observed during exposure to rain, weathering, and long-time immersion.

The Mechanical, Thermal, and Chemical Properties of PLA-Mg Filaments Produced via a Colloidal Route for Fused-Filament Fabrication.

The effect of Mg particles on the thermal, chemical, physical, and primarily mechanical properties of 3D-printed PLA/Mg composites is studied in this paper. Recently, new colloidal processing has been proposed to introduce Mg particles into the PLA matrix, which ensures good dispersion of the particles and better thermal properties, allowing for thermal processing routes such as extrusion or 3D printing via fused-filament fabrication. The thermal and physical properties are here studied in 1D single-filament-printed PLA/Mg composites with 0 to 10 wt.% of Mg particles by Differential Scanning Calorimetry (DSC); we analyse the PLA chain modifications produced, the crystallinity fraction, and the different crystalline forms of the PLA after thermal processing. Fourier Transform Infrared Spectroscopy (FTIR) is used to confirm the influence of the PLA/Mg colloidal processing after printing. The mechanical properties are measured with a universal tensile test machine on the 1D single-printed filaments via fused-filament fabrication (FFF); the filaments were naturally aged to stable conditions. Filaments with and without a notch are studied to obtain the materials' tensile strength, elastic modulus, and fracture toughness. Different analytical models to explain the results of the PLA-Mg were studied, in which the minimum values for the interface strength of the PLA-Mg composites were calculated.

In situ transformation of TiO2 hierarchical nanostructures toward efficient photoelectrochemical water splitting

TiO2 hierarchical nanomaterials have been intensively investigated as a very promising photoanode in photoelectrochemical water splitting due to its combined effects of large surface area and fast electron transfer. However, the TiO2 hierarchical nanostructures prepared by most prevailing synthesis methods currently are at distinct disadvantages such as complicated process, poor controllability, poor interfacial contact, excessive impurities and so on. Here we report a facile route to construct a well-defined TiO2 hierarchical nanostructure via in-situ transformation of TiO2 nanoparticles with highly exposed {001} facets in the tube wall of the pristine TiO2 nanotube arrays. The resulted TiO2 hierarchical nanostructures exhibit enhanced light harvesting, lowe recombination rate of photo-generated charger carrier. Upon these synergistic effects, the target hierarchical nanostructure shows significantly improved PEC performance and excellent photo-switching response with good reproducibility and stability. Corresponding photocurrent density and photon-to-current efficiency achieve 0.76 mA cm−2 and 0.50%, respectively, which show an enhancement of 1.70 and 1.32 times to those of the control one. This work provides a possible route for fabrication of TiO2 starting materials with decent efficiencies.

Rapid and facile fabrication of hierarchically porous graphene aerogel for oil-water separation and piezoresistive sensing applications

Graphene aerogel (GA) holds great potentials for versatile applications, for example, oil-water separation and piezoresistive sensing. However, GA is generally prepared via time-consuming and complicated methods. Herein, a rapid and facile approach has been proposed to fabricate GA by a two-step reduction method, i.e., hydrothermal reduction by thiourea at a mild temperature of 95 °C for 30 min followed by microwave treatment for several seconds, c.a., 4–12 s. GA was partially reduced in the first step and self-assembled into a 3D scaffold which is much more receptive to microwaves and promotes the second complete reduction by microwave treatment. By tuning the microwaving time, the GA microwaved for 10 s, that is, MGA-10 exhibits hierarchically porous microstructure, ultra-low density, and super compressibility. MGA-10 can be used as a recyclable absorbent with high absorption capacities (223 ∼ 430 g/g) towards various oils and organic solvents. Meanwhile, the high sensitivity of the electric resistance to the compressive strain enables MGA-10 promising for pressure sensor applications. The MGA-10 sensor demonstrates high sensitivity (1.112 kPa−1 at a pressure range of 0 ∼ 0.3 kPa) and excellent stability (>3000 cycles). This fabrication route paves the way to efficiently prepare highly compressible graphene aerogels for versatile applications.

Recent progress in additive manufacturing of bulk MAX phase components: A review

The MAX phases are a group of layered ternary, quaternary, or quinary compounds with characteristics of both metals and ceramics. Over recent decades, the synthesis of bulk MAX phase parts for wider engineering applications has gained increasing attention in aerospace, nuclear, and defence industries. The recent adoption of additive manufacturing (AM) technologies in MAX phase fabrication is a step forward in this field. This work overviews the recent progress in additive manufacturing (AM) of bulk MAX phases along with the achieved geometric features, microstructures, and properties after briefing the conventional powder sintering methods of fabricating MAX phase components. Critical challenges associated with these innovative AM-based methods, including, poor AM processability, low MAX phase purity, and insufficient geometric accuracy of the final parts, are also discussed. Accordingly, outlooks for the immediate future in this area are discussed based on the optimization of present fabrication routes and the potential of other AM technologies.

Ionic/Electronic Dual‐Conductor Coating Layer Fabrication Enabling High‐Performance Silicon Anode

Silicon (Si) has received special attention from both scientific research and corporate development for overcoming the current energy density bottleneck. However, the severe volume change and violent interfacial reaction diminish the full benefits of Si material and hamper its direct commercial utilization. Particle pulverization and the companied ionic/electronic isolation are regarded as the intrinsic reason for performance attenuation. Hence, a strategy that can maintain both electronic and ionic conductance on Si anode during the electrochemical process is of great significant for performance improvement and future commercial promotion. Accordingly, an ionic/electronic dual‐conductor coating layer fabrication route is done by in situ building Li4SiO4 fast ion conductor coating layer and implanting electron conduction network, labeled as Si@Li4SiO4/amorphous carbon (C)/carbon nanotubes (CNTs). Notably, the Si@Li4SiO4/C/CNT electrode delivers excellent long‐term cycling stability and prominent rate capability. These results demonstrate that the in situ‐formed fast ionic conductor coating layer facilitates the rapid Li+ diffusion, and the 3D network structure constructed by CNTs and amorphous carbon (polyvinylpyrrolidone‐derived carbon) effectively reinforce the structural stability and keep the electrical connection for the electrode. This study provides an ionic/electronic dual‐conductor coating design concept for Si‐based anode materials.

Fabrication of Ionic Cellulose Nanofiber Composites by Electrospinning Cellulose Microfibril-Gel-Dispersions in Poly(vinyl Alcohol) Solution

ABSTRACT In this study, we propose a fabrication method to obtain composites of poly(vinyl alcohol) (PVA)/ionic cellulose nanofibers, in which a fiber structure is manipulated through a reconstruction of 2,2,6,6-tetramethyl-piperidinyl-1-oxyl radical (TEMPO)-oxidized cellulose nanofiber (TCNF) or the carboxymethyl cellulose nanofiber (CMCNF) heterogeneous microfibril gels using electrospinning method. The key concept is to assemble nanofibers from thin few-nanometer-scale width cellulose nanofibers (microfibrils) to thicker several-hundred-nanometer-scale width cellulose nanofibers by electrospinning insoluble microfibril-gel-dispersion in PVA solution. In the case of CMCNF, nanofibers with less-fused structures were successfully reconstructed via electrospinning. Energy-dispersive X-ray spectroscopy revealed that sodium ions exist in the fibers, where they function as counter ions of carboxylate groups of polyelectrolyte moiety of CMCNF. Thus, the obtained composites do contain both ionic cellulose nanofibers and PVA. The proposed fabrication route can be used to fabricate composites as nonwoven fabrics of polyelectrolyte nanofibers. These natural polymer based ionic fabrics will be widely useful to propose low-environmental-impact polymer actuators and active sensing elements involving the ion transport phenomena.

Study of the Mechanical Properties of the Copper Matrix Composites (CMCs): A Review

Copper matrix composites (CMCs) are known to be lightweight and possess competent mechanical properties, hence is highly suitable for a broad range of advanced applications. Its significance in aerospace, marine, and structural domains make it worthwhile to be investigatedfor low-cost manufacturing and selection of appropriate reinforcements. A comprehensive understanding of CMCs in terms of its fabrication methodologies and the diverse properties achievable through the incorporation of discrete reinforcement materials are essential to beexplored. Given, this manuscript evaluates the distinct methodologies for the preparation of CMCs through various fabrication routes. Besides, the substantial improvement/variation in properties such as mechanical (strength, toughness, hardness and creep), metallurgical (microstructure, grain size and grain boundaries), thermal properties (thermal conductivity, coefficient of thermal expansion) and tribological properties (friction, wear) through the incorporation of reinforcements (additives/filler materials/adhesives) of CMCs also is brought under detailed discussion.

Aerosol Jet Printed Organic Memristive Microdevices Based on a Chitosan:PANI Composite Conductive Channel

In this study we show a chitosan:polyaniline (CPA)-based ink, responding to eco-biofriendly criteria, specifically developed for the manufacturing of the first organic memristive device (OMD) with an aerosol jet printed conductive channel. Our contribution is in the context of bioelectronics, where there is an increasing interest in emulating neuromorphic functions. In this framework, memristive devices and systems have been shown to be well suited. In particular organic-based devices are envisaged as very promising in some applications, such as brain–machine interfacing, owing to specific properties of organics (e.g., biocompatibility, mixed ionic–electronic conduction). On the other hand, the research activities on flexible organic (bio)electronic devices and direct writing (DW) noncontact techniques increasingly overlap in the effort of achieving reliable applications benefiting from the rapid prototyping to accomplish a fast device optimization. In this context, ink-based techniques, such as aerosol jet printing (AJP), although particularly well suited to implement 3D-printed electronics due to advantages it offers in terms of a wide set of allowed printable materials, still require research efforts aimed at conferring printability to the desired precursors. The developed CPA composite was characterized by FTIR, DLS, and MALDI-TOF techniques, while the related aerosol jet printed films were studied by SEM and profilometry. Taking advantage of the intrinsic and stable electrical conductivity of CPA films, which do not necessarily require any acidic treatment to promote a sustained charge carrier conduction, 10 μm short-channel OMDs were hence manufactured by interfacing the printed CPA layers with a solid polyelectrolyte (SPE). We accordingly demonstrated prototypes of stable and best performing OMD devices with downscaled features, showing well-defined counterclockwise hysteresis/rectification and an enhanced durability. These properties pave the way to further improving performance, as well as to realizing a direct integration of the devices into hardware neural networks by in-line fabrication routes.

Optimized Route for the Fabrication of MnAlC Permanent Magnets by Arc Melting

The rare-earth-free MnAlC alloy is currently considered a very promising candidate for permanent magnet applications due to its high anisotropy field and relatively high saturation magnetization and Curie temperature, besides being a low-cost material. In this work, we presented a simple fabrication route that allows for obtaining a magnetically enhanced bulk τ-MnAlC magnet. In the fabrication process, an electric arc-melting method was carried out to melt ingots of MnAlC alloys. A two-step solution treatment at 1200 °C and 1100 °C allowed us to synthesize a pure room-temperature ε-MnAlC ingot that completely transformed into τ-MnAlC alloy, free of secondary phases, after an annealing treatment at 550 °C for 30 min. The Rietveld refinements and magnetization measurements demonstrated that the quenched process produces a phase-segregated ε-MnAlC alloy that is formed by two types of ε-phases due to local fluctuation of the Mn. Room-temperature hysteresis loops showed that our improved τ-MnAlC alloy exhibited a remanent magnetization of 42 Am2/kg, a coercive field of 0.2 T and a maximum energy product, (BH)max, of 6.07 kJ/m3, which is higher than those reported in previous works using a similar preparation route. Experimental evidence demonstrated that the synthesis of a pure room-temperature ε-MnAlC played an important role in the suppression of undesirable phases that deteriorate the permanent magnet properties of the τ-MnAlC. Finally, magnetic images recorded by Lorentz microscopy allowed us to observe the microstructure and magnetic domain walls of the optimized τ-MnAlC. The presence of magnetic contrasts in all the observed grains allowed us to confirm the high-quality ferromagnetic behavior of the system.

Broadband nanoplasmonic photodetector fabricated in ambient condition

Surface plasmon are widely used to promote the exciton generation and light absorption in solar cells and photodetectors. In this work, a feasible approach for UV–vis-NIR photodetection using plasmon-enhanced silicon nanowires (SiNWs) and amorphous TiO2 heterostructure is presented. The photodetector shows excellent photo response up to 3.3 orders of magnitude enhancement with rise/decay times of 77/51 μs. Under small external bias (1V), the photodetector exhibits very high responsivity up to 49 A W−1 over a broadband wavelength range from 300–1100 nm. All the experimental procedures are performed at room temperature in ambient conditions. Its simple fabrication route and excellent performance make this photodetector distinct from similar architectures. Our finding offers new opportunities to engineer plasmon-based nanostructures in chemical sensors, optoelectronics and nanophotonic devices and applications.

Injection Molding of Thermoplastics for Low-Cost Nanofluidic Devices

Thermoplastic micro- and nanofluidics are increasing in popularity due to their favorable chemical and physical properties as an alternative to poly(dimethyl siloxane) (PDMS)-based devices, which are more widely used in academia. Additionally, their fabrication is compatible with industrial processes, such as hot embossing and injection molding. Nevertheless, producing devices with sub-micrometer channel heights and low roughness while retaining high-throughput molding remains challenging. This article details the combination of grayscale e-beam lithography (g-EBL) and injection molding as a fabrication route for capillary 3D thermoplastic nanofluidic devices with unprecedented accuracy in the sub-micrometer range. We employed g-EBL to pattern the device profile in a poly(methyl methacrylate) (PMMA)-based resist, which served as a substrate for the subsequent fabrication of a negative nickel mold by using electroforming. These molds are used to fabricate devices in PMMA and cyclic olefin polymers (COP) using injection molding. We show that the 3D height profile of the nanofluidic devices is maintained throughout the entire replication cycle within very tight tolerances, retaining its nanoscale topography on a millimeter-length scale. Moreover, somewhat surprisingly, the roughness in the inflow section of the devices was significantly reduced, which we attribute to the nickel mold fabrication. Last, we show that the capillary-driven devices can be used to size-dependently trap nanoparticles of various sizes in a reliable and facile manner while only requiring a 4 μL sample volume. The presented device and fabrication procedure paves the way for applications in various scientific fields, ranging from immunology to neurology and material science, in a cost-effective manner.

A Novel Magnetic Hardening Mechanism for Nd‐Fe‐B Permanent Magnets Based on Solid‐State Phase Transformation

AbstractPermanent magnets based on neodymium‐iron‐boron (Nd‐Fe‐B) alloys provide the highest performance and energy density, finding usage in many high‐tech applications. Their magnetic performance relies on the intrinsic properties of the hard‐magnetic Nd2Fe14B phase combined with control over the microstructure during production. In this study, a novel magnetic hardening mechanism is described in such materials based on a solid‐state phase transformation. Using modified Nd‐Fe‐B alloys of the type Nd16Febal‐x‐y‐zCoxMoyCuzB7 for the first time it is revealed how the microstructural transformation from the metastable Nd2Fe17Bx phase to the hard‐magnetic Nd2Fe14B phase can be thermally controlled, leading to an astonishing increase in coercivity from ≈200 kAm−1 to almost 700 kAm−1. Furthermore, after thermally treating a quenched sample of Nd16Fe56Co20Mo2Cu2B7, the presence of Mo leads to the formation of fine FeMo2B2 precipitates, in the range from micrometers down to a few nanometers. These precipitates are responsible for the refinement of the Nd2Fe14B grains and so for the high coercivity. This mechanism can be incorporated into existing manufacturing processes and can prove to be applicable to novel fabrication routes for Nd‐Fe‐B magnets, such as additive manufacturing.

Shape memory polymer composites (SMPCs) using interconnected nanowire network foams as reinforcements

Shape memory polymers (SMPs), although offer a suite of advantages such as ease of processability and lower density, lag behind their shape memory alloy counterparts, in terms of mechanical properties such as recovery stress and cyclability. Reinforcing SMPs with inorganic nanowires and carbon nanotubes (CNTs) is a sought-after pathway for tailoring their mechanical properties. Here, inorganic nanowires also offer the added advantage of covalently binding the fillers to the surrounding polymer matrices via organic molecules. The SMP composites (SMPCs) thus obtained have well-engineered nanowire-polymer interfaces, which could be used to tune their mechanical properties. A well-known method of fabricating SMPCs involving casting dispersions of nanowires (or CNTs) in mixtures of monomers and crosslinkers typically results in marginal improvements in the mechanical properties of the fabricated SMPCs. This is owed to the constraints imposed by the rule-of-mixture principles. To circumvent this limitation, a new method for SMPC fabrication is designed and presented. This involves infiltrating polymers into pre-fabricated nanowire foams. The pre-fabricated foams were fabricated by consolidating measured quantities of nanowires and a sacrificial material, such as (NH4)2CO3, followed by heating the consolidated mixtures for subliming the sacrificial material. Similar to the case of traditional composites, use of silanes to functionalize the nanowire surfaces allowed for the formation of bonds between both the nanowire-nanowire and the nanowire-polymer interfaces. SMPCs fabricated using TiO2 nanowires and SMP composed of neopentyl glycol diglycidyl ether and poly(propylene glycol) bis(2-aminopropyl ether) (Jeffamine D230) in a 2:1 molar ratio exhibited a 300% improvement in the elastic modulus relative to that of the SMP. This increase was significantly higher than SMPC made using the traditional fabrication route. Well-known powder metallurgy techniques employed for the fabrication of these SMPCs make this strategy applicable for obtaining other SMPCs of any desired shape and chemical composition.

Immobilised TiO2 Mesocrystals with Exposed {001} Facets for Efficient Dye‐Sensitized Solar Cells

The immobilization of titanium dioxide is necessary for several energy and environmental applications such as dye‐sensitized solar cells (DSSCs). A two‐step fabrication route has been developed in this work including a near room temperature hydrolysis reaction to produce immobilized (NH4)2TiOF4 arrays, followed by successive topotactic transformations to immobilised TiO2 mesocrystals (imcTiO2). Hierarchical mesocrystal structure has thereby been successfully introduced to immobilised TiO2 without the use of expensive equipment or complex strategies. Thanks to the features of the nano‐building blocks such as high surface area and high active {001} facets; collective properties including the common orientation of nanoparticles; and strong adhesion to the substrate inherited from the immobilized (NH4)2TiOF4 precursor, the imcTiO2 possesses a high dye pickup capability and optimal electron transport ability. The average power conversion efficiency from imcTiO2 based DSSCs is comparable to devices with two layers of printed commercial TiO2 under the same sintering condition, with the balanced short circuit current densities, similar open‐circuit voltages, and outstanding fill factors.