Versatile Fabrication Method Research Articles

3D Printing of NiZn ferrite/ABS Magnetic Composites for Electromagnetic Devices

ABSTRACT3D printing is a versatile fabrication method that offers the potential to realize complex 3D devices with metamaterial characteristics in a single process directly from a computer aided design. However, the range of functional devices that might be realized by 3D printing is limited by the current range of materials that are compatible with a given 3D printing process: fused deposition modelling (FDM), which is a widely used 3D printing method, typically employs only common thermoplastics. Here we describe the development of a magnetic feedstock based on polymer-ferrite composite that is compatible with FDM. The feasibility of the technique is demonstrated by the permittivity and permeability measurement of direct printed blocks and the fabrication of a complex 3D diamond-like lattice structure. The development of printable magnetic composites provides increased design freedom for direct realization of devices with graded electromagnetic properties operating at microwave frequencies.

Electrospinning of Nanofibers and Their Applications for Energy Devices

With the depletion of fossil fuels and the increasing demand of energy for economic development, it is urgent to develop renewable energy technologies to sustain the economic growth. Electrospinning is a versatile and efficient fabrication method for one‐dimensional (1D) nanostructured fibers of metals, metal oxides, hydrocarbons, composites, and so forth. The resulting nanofibers (NFs) with controllable diameters ranging from nanometer to micrometer scale possess unique properties such as a high surface‐area‐to‐volume and aspect ratio, low density, and high pore volume. These properties make 1D nanomaterials more advantageous than conventional materials in energy harvesting, conversion, and storage devices. In this review, the key parameters for e‐spinning are discussed and the properties of electrospun NFs and applications in solar cells, fuel cells, nanogenerators, hydrogen energy harvesting and storage, lithium‐ion batteries, and supercapacitors are reviewed. The advantages and disadvantages of electrospinning and an outlook on the possible future directions are also discussed.

Template-Guided Self-Assembly of Discrete Optoplasmonic Molecules and Extended Optoplasmonic Arrays

Abstract The integration of metallic and dielectric building blocks into optoplasmonic structures creates new electromagnetic systems in which plasmonic and photonic modes can interact in the near-, intermediate- and farfield. The morphology-dependent electromagnetic coupling between the different building blocks in these hybrid structures provides a multitude of opportunities for controlling electromagnetic fields in both spatial and frequency domain as well as for engineering the phase landscape and the local density of optical states. Control over any of these properties requires, however, rational fabrication approaches for well-defined metal-dielectric hybrid structures. Template-guided self-assembly is a versatile fabrication method capable of integrating metallic and dielectric components into discrete optoplasmonic structures, arrays, or metasurfaces. The structural flexibility provided by the approach is illustrated by two representative implementations of optoplasmonic materials discussed in this review. In optoplasmonic atoms or molecules optical microcavities (OMs) serve as whispering gallery mode resonators that provide a discrete photonic mode spectrum to interact with plasmonic nanostructures contained in the evanescent fields of the OMs. In extended hetero-nanoparticle arrays in-plane scattered light induces geometry-dependent photonic resonances that mix with the localized surface plasmon resonances of the metal nanoparticles.We characterize the fundamental electromagnetic working principles underlying both optoplasmonic approaches and review the fabrication strategies implemented to realize them.

Dip TIPS as a facile and versatile method for fabrication of polymer foams with controlled shape, size and pore architecture for bioengineering applications.

The porous polymer foams act as a template for neotissuegenesis in tissue engineering, and, as a reservoir for cell transplants such as pancreatic islets while simultaneously providing a functional interface with the host body. The fabrication of foams with the controlled shape, size and pore structure is of prime importance in various bioengineering applications. To this end, here we demonstrate a thermally induced phase separation (TIPS) based facile process for the fabrication of polymer foams with a controlled architecture. The setup comprises of a metallic template bar (T), a metallic conducting block (C) and a non-metallic reservoir tube (R), connected in sequence T-C-R. The process hereinafter termed as Dip TIPS, involves the dipping of the T-bar into a polymer solution, followed by filling of the R-tube with a freezing mixture to induce the phase separation of a polymer solution in the immediate vicinity of T-bar; Subsequent free-drying or freeze-extraction steps produced the polymer foams. An easy exchange of the T-bar of a spherical or rectangular shape allowed the fabrication of tubular, open- capsular and flat-sheet shaped foams. A mere change in the quenching time produced the foams with a thickness ranging from hundreds of microns to several millimeters. And, the pore size was conveniently controlled by varying either the polymer concentration or the quenching temperature. Subsequent in vivo studies in brown Norway rats for 4-weeks demonstrated the guided cell infiltration and homogenous cell distribution through the polymer matrix, without any fibrous capsule and necrotic core. In conclusion, the results show the “Dip TIPS” as a facile and adaptable process for the fabrication of anisotropic channeled porous polymer foams of various shapes and sizes for potential applications in tissue engineering, cell transplantation and other related fields.

Toward larger DNA origami.

Structural DNA nanotechnology, and specifically scaffolded DNA origami, is rapidly developing as a versatile method for bottom-up fabrication of novel nanometer-scale materials and devices. However, lengths of conventional single-stranded scaffolds, for example, 7,249-nucleotide circular genomic DNA from the M13mp18 phage, limit the scales of these uniquely addressable structures. Additionally, increasing DNA origami size generates the cost burden of increased staple-strand synthesis. We addressed this 2-fold problem by developing the following methods: (1) production of the largest to-date biologically derived single-stranded scaffold using a λ/M13 hybrid virus to produce a 51 466-nucleotide DNA in a circular, single-stranded form and (2) inexpensive DNA synthesis via an inkjet-printing process on a chip embossed with functionalized micropillars made from cyclic olefin copolymer. We have experimentally demonstrated very efficient assembly of a 51-kilobasepair origami from the λ/M13 hybrid scaffold folded by chip-derived staple strands. In addition, we have demonstrated two-dimensional, asymmetric origami sheets with controlled global curvature such that they land on a substrate in predictable orientations that have been verified by atomic force microscopy.

Fabrication of chiral plasmonic oligomers using cysteine-modified gold nanorods as monomers

Generation of circular dichroism (CD) beyond the UV region is of great interest in developing chiral sensors and chiroptical devices. Herein, we demonstrate a simple and versatile method for fabrication of plasmonic oligomers with strong CD response in the visible and near IR spectral range. The oligomers were fabricated by triggering the side-by-side assembly of cysteine-modified gold nanorods. The modified nanorods themselves did not exhibit obvious plasmonic CD signals; however, the oligomers show strong CD bands around the plasmon resonance wavelength. The sign of the CD band was dictated by the chirality of the absorbed cysteine molecules. By adjusting the size of the oligomers, the concentration of chiral molecules, and/or the aspect ratio of the nanorods, the CD intensity and spectral range were readily tunable. Theoretical calculations suggested that CD of the oligomers originated from a slight twist of adjacent nanorods within the oligomer. Therefore, we propose that the adsorbed chiral molecules are able to manipulate the twist angles between the nanorods and thus modulate the CD response of the oligomers.

Electrospun fibrous scaffolds of Poly(glycerol-dodecanedioate) for engineering neural tissues from mouse embryonic stem cells.

For tissue engineering applications, the preparation of biodegradable and biocompatible scaffolds is the most desirable but challenging task. Among the various fabrication methods, electrospinning is the most attractive one due to its simplicity and versatility. Additionally, electrospun nanofibers mimic the size of natural extracellular matrix ensuring additional support for cell survival and growth. This study showed the viability of the fabrication of long fibers spanning a larger deposit area for a novel biodegradable and biocompatible polymer namedpoly(glycerol-dodecanoate) (PGD)(1) by using a newly designed collector for electrospinning. PGD exhibits unique elastic properties with similar mechanical properties to nerve tissues, thus it is suitable for neural tissue engineering applications. The synthesis and fabrication set-up for making fibrous scaffolding materials was simple, highly reproducible, and inexpensive. In biocompatibility testing, cells derived from mouse embryonic stem cells could adhere to and grow on the electrospun PGD fibers. In summary, this protocol provided a versatile fabrication method for making PGD electrospun fibers to support the growth of mouse embryonic stem cell derived neural lineage cells.

Sub-15-nm patterning of asymmetric metal electrodes and devices by adhesion lithography.

Coplanar electrodes formed from asymmetric metals separated on the nanometre length scale are essential elements of nanoscale photonic and electronic devices. Existing fabrication methods typically involve electron-beam lithography—a technique that enables high fidelity patterning but suffers from significant limitations in terms of low throughput, poor scalability to large areas and restrictive choice of substrate and electrode materials. Here, we describe a versatile method for the rapid fabrication of asymmetric nanogap electrodes that exploits the ability of selected self-assembled monolayers to attach conformally to a prepatterned metal layer and thereby weaken adhesion to a subsequently deposited metal film. The method may be carried out under ambient conditions using simple equipment and a minimum of processing steps, enabling the rapid fabrication of nanogap electrodes and optoelectronic devices with aspect ratios in excess of 100,000.

Dynamically bonded layer‐by‐layer films: Dynamic properties and applications

ABSTRACTLayer‐by‐layer (LBL) assembly, a simple but versatile method for thin film fabrication, has been widely employed to fabricate nanoengineered films with controlled composition and thickness. Dynamically bonded LBL films are films fabricated using dynamic bonds, that is, chemical bonds which can undergo reversible breaking and reformation usually under equilibrium conditions, as driving forces. Because of the reversible, dynamic nature of the dynamic bonds, these films exhibit various dynamic properties, ranging from a small scale movement of the polymer chains within the films (chain rearrangement), to a large scale movement of the chains, which results in film disintegration. Usually an external stimulus is used to trigger the response of a dynamic film. Novel applications have been proposed by exploiting the dynamic properties of these films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40918.

Hole-mask colloidal nanolithography combined with tilted-angle-rotation evaporation: A versatile method for fabrication of low-cost and large-area complex plasmonic nanostructures and metamaterials

Many nano-optical applications require a suitable nanofabrication technology. Hole-mask colloidal nanolithography has proven to be a low-cost and large-area alternative for the fabrication of complex plasmonic nanostructures as well as metamaterials. In this paper, we describe the fabrication process step by step. We manufacture a variety of different plasmonic structures ranging from simple nano-antennas over complex chiral structures to stacked composite materials for applications such as sensing. Additionally, we give details on the control of the nanostructure lateral density which allows for the multilayer-fabrication of complex nanostructures. In two accompanying movies, the fabrication strategy is explained and details are being demonstrated in the lab. The movies can be found at the website of Beilstein TV.

Sandwich Approach toward Inverse Opals with Linear and Nonlinear Optical Functionalities

Three-dimensionally ordered macroporous materials have unique structural and optical properties, making them useful for numerous applications in catalysis, membrane science, and optics. Accessible and economic fabrication of these materials is essential to fully explore the many possibilities that these materials present. A new templating method to fabricate three-dimensionally ordered macroporous materials without overlayers is presented. The resulting structures are freestanding inverse opals with large-area uniformity. The versatility and power of our fabrication method is demonstrated by synthesizing inverse opals displaying fluorescence, chirality, upconversion, second harmonic generation, and third harmonic generation. This economical and versatile fabrication method will facilitate research on inverse opals in general and on linear and nonlinear optical effects in 3D photonic crystals specifically. The relative ease of synthesis and wide variety of resulting materials will help the characterization and improvement of existing anomalous dispersion effects in these structures, while providing a platform for the discovery and demonstration of novel effects.

Dual-porosity hollow nanoparticles for the immunoprotection and delivery of nonhuman enzymes.

Although enzymes of nonhuman origin have been studied for a variety of therapeutic and diagnostic applications, their use has been limited by the immune responses generated against them. The described dual-porosity hollow nanoparticle platform obviates immune attack on nonhuman enzymes paving the way to in vivo applications including enzyme-prodrug therapies and enzymatic depletion of tumor nutrients. This platform is manufactured with a versatile, scalable, and robust fabrication method. It efficiently encapsulates macromolecular cargos filled through mesopores into a hollow interior, shielding them from antibodies and proteases once the mesopores are sealed with nanoporous material. The nanoporous shell allows small molecule diffusion allowing interaction with the large macromolecular payload in the hollow center. The approach has been validated in vivo using l-asparaginase to achieve l-asparagine depletion in the presence of neutralizing antibodies.

High Precision Fabrication and Positioning of Nanoelectrodes in a Nanopore

A simple and versatile method for the direct fabrication of tunneling electrodes with controllable gap distance by using electron-beam-induced deposition (EBID) is presented. We show that tunneling nanogaps smaller than the minimum feature size realizable by conventional EBID can be achieved with a standard scanning electron microscope. These gaps can easily be embedded in nanopores with high accuracy. The controllability of this fabrication method and the nanogap geometry was verified by SEM and TEM imaging. Furthermore, tunneling spectroscopy in a group of solvents with different barrier heights was used to determine the nanogap functionality. Ultimately, the presented fabrication method can be further applied for the fabrication of arrays of nanogap/nanopores or nanogap electrodes with tunable electrode materials. Additionally, this method can also offer direct fabrication of nanoscale electrode systems with tunable spacing for redox cycling and plasmonic applications, which represents an important step in the development of tunneling nanopore structures and in enhancing the capabilities of nanopore sensors.

Origin of nanohole formation by etching based on droplet epitaxy

Creating and manipulating materials at the nanoscale with controllable size, shape and nucleation site is an important task to meet the urgent demands for quantum structures with designed properties. In the last ten years, droplet epitaxy has been emerging as a versatile fabrication method for various complex nanostructures, such as quantum dots, quantum rings, double-rings, and so on. However, there is a lack of understanding of the deep nanohole formation based on droplet epitaxy at a high substrate temperature. Here we fabricate self-organized GaAs nanoholes by Ga droplet etching at high temperature based on droplet epitaxy, and they present good optoelectronic properties and have promising applications in fabrication of nanodevices due to their unique topology. A theoretical model is correspondingly proposed to explain the basic mechanism and simulate the time evolution of the nanohole structures. Our analysis shows that the morphology of the nanohole nanostructures can be well controlled through regulating experimental conditions.

Layer-by-layer Nanoarchitectonics: Invention, Innovation, and Evolution

Abstract Materials fabrication with nanoscale structural precision based on bottom-up-type self-assembly has become more important in various current disciplines in chemistry including materials chemistry, organic chemistry, physical chemistry, analytical chemistry, biochemistry, colloid and surface chemistry, and supramolecular chemistry. Although the design of new materials based on nanoscale self-assembly is anticipated as a key concept, preparing complete three-dimensional structures at nanoscale precision remains a difficult target using current technologies. Rather, dimension-reduced approaches such as layering of two-dimensional nanostructures into precisely controlled lamellar nanomaterials are currently achievable. In particular, layer-by-layer (LbL) assembly is known as a highly versatile method for fabrication of controlled layered structures from various kinds of component materials using very simple, inexpensive, and rapid procedures. Therefore, fabrication of multilayer films through the LbL deposition process has attracted growing interest from various research communities. The high versatility and flexibility of LbL assembly is continuously creating new concepts, new materials, new procedures, and new applications. In this highlight review, we focus on nanoarchitectonics by LbL assembly. After an initial introduction on the invention and a brief history of the LbL assembly technique, innovations and the evolution of the technique are described based mainly on recent examples, which are categorized into two sections: (i) developments in methodology (technical, material, and phenomenological aspects with expansion of concept) and (ii) progress in applications (physical, chemical/biochemical, and biomedical applications).

High aspect ratio semiconducting nanostructure random networks: highly versatile materials for multiple applications

Abstractmagnified imageIn this work we demonstrate that, based on a simple and versatile fabrication method, the collective use and integration of high aspect ratio (AR) nanostructures, here Si and ZnO nanowires (NWs), is possible and addresses multiple application fields, including light detection, active materials for bio‐sensing devices, or materials with interesting wettability properties. A suitable implementation of the filtration method enables then to design networks composed of semiconducting NWs with AR in the range of 10–400. Even for the lowest AR, the network is coherent. However, good electrical properties and flexibility are obtained only for AR greater than 50.magnified imageSi nanowire (SiNW) random networks observed by SEM: Large magnification showing the nanowires and low magnification showing the electrical test structure.(© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Self‐Assembly of Multiple Stacked Nanorings by Vertically Correlated Droplet Epitaxy

Fabrication of advanced artificial nanomaterials is a long‐term pursuit to fulfill the promises of nanomaterials. In the last ten years, Droplet Epitaxy has been emerging as a versatile fabrication method for various complex nanomaterials, but there is a lack of growth protocol to control the growth vertically. Here we report a vertically correlated Droplet Epitaxy growth method. We find that the nanodroplets form preferable on the preexisting nanorings, which enables fabrication of vertically aligned nanostructures by Droplet Epitaxy. Nucleation thermodynamics and growth kinetics have been proposed to explain the vertically correlated Droplet Epitaxy. Heterojunctions can be realized at nanoscale by the presented method. In addition, the nucleation thermodynamics of nanodroplets observed in this article will allow site‐controlled fabrication of nanostructures.

Simple and rapid fabrication of large-area 2D colloidal crystals for nanopatterning of conducting polymers

Here we demonstrate a versatile and simple method for the rapid fabrication of two-dimensional (2D) colloidal crystals as the template for nanopatterning of conducting polymer. Our method involves the electrophoretic deposition of negatively-charged colloidal particles on an indium tin oxide (ITO) electrode and the formation of 2D colloidal crystals at the air-water interface by the dipping of the colloidal assembly on the electrode. On the dipping step, the particles were spread from the electrode and self-assembled into the hexagonally close-packed 2D colloidal crystals floating at the air-water interface. The obtained colloidal crystals could be transferred to various substrates and stacked into three-dimensional (3D) colloidal crystals of the controlled number of layers by simply repeating the transfer procedure. Based on the proposed technique, the fabrication of 2D colloidal crystal patterns by a soft lithographic technique and the fabrication of nanostructured conducting polymers with a template using the prepared 2D colloidal crystals were demonstrated. The proposed method does not require complicated equipment or the precise control of experimental conditions, which is expected to be useful in the nanostructure fabrication.

Highly Efficient Wettability Control via Three-Dimensional (3D) Suspension of Titania Nanoparticles in Polystyrene Nanofibers

Electrospinning is a simple and highly versatile method for the large-scale fabrication of polymeric nanofibers. Additives or fillers can also be used to functionalize the nanofibers for use in specific applications. Herein, we demonstrate a novel and efficient way to fabricate superhydrophobic to hydrophilic tunable mats with the combined use of electrospinning and electrospraying that may be suitable for mass production on the merits of rapid deposition. The tunable nanocomposite mats were comprised of hydrophobic polystyrene nanofibers and hydrophilic titania nanoparticles. When the electrical conductivity of the electrospinning solution was increased, the surface morphology of the mats changed noticeably from a bead-on-string structure to an almost bead-free structure. Polystyrene (PS)-titania nanocomposite mats initially yielded a static water contact angle as high as 140° ± 3°. Subsequently exposing these mats with relatively weak ultraviolet irradiation (λ = 365 nm, I = 0.6 mW/cm²) for 2 h, the unique 3D suspension of the photoactive titania nanoparticles maximized the hydrophilic performance of the mats, reducing the static water contact angle to as low as 26° ± 2°. The tunable mats were characterized by scanning electron microscopy (SEM), static water contact angle (WCA) measurements, and energy-dispersive X-ray spectroscopy (EDX). Our findings confirmed that the tunable mats fabricated by the simultaneous implementation of electrospraying and electrospinning had the most efficient ultraviolet (UV)-driven wettability control in terms of cost-effectiveness. Well-controlled tunable hydrophobic and hydrophilic mats find potential applications in functional textiles, environmental membranes, biological sensors, scaffolds, and transport media.

Lithographically Patterned Electrodeposition of Gold, Silver, and Nickel Nanoring Arrays with Widely Tunable Near-Infrared Plasmonic Resonances

A novel low-cost nanoring array fabrication method that combines the process of lithographically patterned nanoscale electrodeposition (LPNE) with colloidal lithography is described. Nanoring array fabrication was accomplished in three steps: (i) a thin (70 nm) sacrificial nickel or silver film was first vapor-deposited onto a plasma-etched packed colloidal monolayer; (ii) the polymer colloids were removed from the surface, a thin film of positive photoresist was applied, and a backside exposure of the photoresist was used to create a nanohole electrode array; (iii) this array of nanoscale cylindrical electrodes was then used for the electrodeposition of gold, silver, or nickel nanorings. Removal of the photoresist and sacrificial metal film yielded a nanoring array in which all of the nanoring dimensions were set independently: the inter-ring spacing was fixed by the colloidal radius, the radius of the nanorings was controlled by the plasma etching process, and the width of the nanorings was controlled by the electrodeposition process. A combination of scanning electron microscopy (SEM) measurements and Fourier transform near-infrared (FT-NIR) absorption spectroscopy were used to characterize the nanoring arrays. Nanoring arrays with radii from 200 to 400 nm exhibited a single strong NIR plasmonic resonance with an absorption maximum wavelength that varied linearly from 1.25 to 3.33 μm as predicted by a simple standing wave model linear antenna theory. This simple yet versatile nanoring array fabrication method was also used to electrodeposit concentric double gold nanoring arrays that exhibited multiple NIR plasmonic resonances.