Single-step Fabrication Research Articles

3D printing and dynamic modeling of a polymer-based bimodal piezoelectric motor

Owing to characteristics of single-step fabrication and rapid prototyping, 3D printing have potential applications in processing piezoelectric motors with complex structures. In this paper, a 3D printed resin-based bimodal piezoelectric motor is proposed. Four slots of the motor are designed to reduce the influence of large damping caused by polymer’s viscoelastic and enhance mechanical properties. Considering the viscoelasticity and internal structure of the stator, a dynamic model based on the proposed motor is developed. Furthermore, parameters of these slots are optimized using the Taguchi method. Prototypes are fabricated and experimentally investigated. The results demonstrate that the first longitudinal mode and the second bending mode are 17 765 Hz and 18 006 Hz respectively, which are consistent with the analytical model results. Under the voltage of 300 Vpp, the maximum no-load speed and maximum driving load of the slotted motor are 200 r min−1 and 20 g with a speed of 6 r min−1, respectively. Compared with the motor without slots, the speed and load capacity are increased by 25% and 33%. Therefore, the motor with slots exhibits better mechanical output performance.

Single-step fabrication of superhydrophobic urchin-like copper oxide nanopowders: Effect of structure-directing agents

The use of superhydrophobic metal oxide nanoparticles has been considered for the construction of self-cleaning, anti-corrosion, anti-icing, anti-fogging, and oil/water separation surfaces, but the low chemical and thermal stabilities of applied organic modifiers restrict their wide applications. In this study, the superhydrophobic copper oxide nanoparticles with the hierarchical urchin, flower and spherical-like architectures were fabricated via a simple and facile single-step hydrothermal method without any post chemical modification. Taguchi experimental design was used to evaluate and optimize the synthesis parameters such as structure-directing agent concentration and its type, synthesis temperature, and the molar ratio of the complexing agent to the initial copper (II) ions. The wettability characteristics of synthesized samples were assessed based on the chemical composition of powders and their morphological structures. The scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analyses were used to characterize the resultant samples. The wettability properties of samples were determined by measuring the water contact angle (WCA) and contact angle hysteresis (CAH). The results confirmed that the synthesized sample under the optimum condition had an excellent superhydrophobic property with a WCA of 158.4⁰±2⁰ and CAH of 1.5⁰. The surface wettability evaluations also revealed that the morphology and surface free energy of the powders could be controlled simultaneously by alterations of type and concentration of the structure-directing agent, in order to enhance the anti-wetteing characteristics.

Single-step fabrication of Na-TUD-1 novel heterogeneous base nano-catalyst for Knoevenagel condensation reaction

This research, for the first time, reports the design and development of a heterogeneous nano-catalyst based on sodium ions (Na+) incorporation in Technical University of Delft (TUD-1) mesoporous silica for Knoevenagel condensation reaction. Facile one-step fabrication of Na-TUD-1 nano-catalysts (varying Si/Na ratio as 100–5) was demonstrated using the sol–gel route. The catalytic performance of Na-TUD-1 was evaluated as a base heterogeneous catalyst in Knoevenagel condensation reaction, which took place under conventional and microwave irradiations conditions using ethanol as a solvent. Na-TUD-1 exhibited superior catalytic activity in comparison to available homogeneous base catalysts such as sodium ethoxide. The Na-TUD-1 nano-catalyst demonstrated identical performance till the fourth run along with high stability and negligible leaching of Na. Moreover, the use of microwave heating reduced the reaction time from 240 to 20 min only with a TOF of 0.58 min−1. Such excellent performance of Na-TUD-1 heterogeneous nano-catalysts will certainly increase its industrial acceptability to achieve affordable and efficient waste-effluent treatments.

Single-Step Fabrication of Core–Shell Microgels for the Controlled Release of rhBMP-2 and Simvastatin to Induce Osteogenesis

Dual delivery of bioactive molecules (drugs and growth factors) has been attempted to enhance multiple processes during tissue regeneration. For bone tissue engineering, many attempts have been mad...

Single step fabrication of spherical CaO pellets via novel agar-assisted moulding technique for high-temperature CO2 capture

CaO sorbents have received extensive attentions in the field of high-temperature CO2 removal due to its outstanding characters of low cost, fast sorption kinetics and high theoretical capacity. Granulating CaO powder into spherical pellets is requisite prior to its commercial application for post-combustion CO2 capture. This work proposed a facile agar-assisted moulding technique for the pelletization of CaO sorbents inspired from the strong coagulability and hydrophobicity of agar powder. In addition, finding efficient calcium precursors to produce CaO sorbents is also crucial to their CO2 sorption performance. Hence, two novel organometallic precursors, i.e., calcium laurate and calcium myristate, were employed in the current work. The obtained CaO sorbents exhibited a high degree of sphericility and uniform sizes of 3–4 mm. Besides, these sorbent pellets presented good CO2 sorption performance. In particular, the pellets using calcium laurate as precursor showed impressive performance, including high sorption rate and carbonation conversion (up to 0.92). The excellent performance was attributed to the rich porosity and porous structures of this sorbent. Such characters were believed to be brought by the burning of agar and organometallic precursors at high temperatures, which resulted in the quick release of large volumes of gases in a short time and, thus, led to the formation of porous structures. In addition, the burning out of the well dispersed agar powder in the sorbent pellet also left abundant pores in situ in the pellets. Generally, the good performance of the prepared CaO pellets demonstrates the effectiveness of the agar-assisted moulding technique for the sorbent granulation and the suitability of calcium laurate as calcium precursor.

Single-step fabrication of oriented composite nanowires by pulsed laser deposition in magnetic field

In this work, we demonstrate a novel way of fabricating oriented composite nanowires consisting of arranged nanoparticles. The structures are produced by an advanced pulsed laser deposition technology involving the simultaneous ablation of two metal targets, Fe and Ag. The depositions are carried out in air at atmospheric pressure in the presence of a magnetic field by using nanosecond laser pulses delivered by a Nd:YAG laser system operating at its fundamental wavelength. Samples are thus produced composed by iron oxide and silver at different percentage ratios. Their morphology represents nanowires with few tens of microns in length and an orientation predominantly following the direction of the magnetic force lines. The study on the optical properties of the structures thus produced revealed plasmon resonance behavior in their transmission spectra with its position depending on the ratio between the two building materials. UV–vis spectra were also obtained with polarized light. Higher transmission was measured for light polarized perpendicular to the length of the nanowires, compared to the case of polarization parallel to the nanowires. The structures can find applications in the design of novel polarization and magneto-optics devices, as well as in nanoelectronics and spintronics.

Effect of solvent absorption on the optical properties of 3D printed methacrylate waveguide

Methacrylate-based photopolymer waveguides are 3D printed using stereolithography as a single-step fabrication technique and the light propagation through these waveguides is investigated in the presence of various solvents. Solvent absorption on the photopolymer surface is found to play a significant role in the optical output power of the waveguide. Swelling of the photopolymer caused by the solvent absorption is found to increase the optical power transmission through the waveguide. Mixing isopropanol and glycerol with DI water separately at specific concentrations so that their respective refractive indices remain similar, it is observed that isopropanol samples increase the optical power by ~36% compared to glycerol samples, which showed optical power enhancement around 4.9%. A first-order optical model is presented that shows the increase in optical power has a spontaneous response due to the change in the refractive index of the waveguide surface upon solvent contact, followed by a dynamic response due to the formation of the swelling layer as the absorbed solvent diffuse inside the polymer. The methacrylate-based waveguide also showed selectivity towards different concentrations of isopropanol. Results from our study show that the optical properties of the given methacrylate-based photopolymer are largely affected by the absorption affinity of the solvent towards the photopolymer rather than the solvent’s refractive index, which can be crucial for designing integrated optical devices using methacrylate-based photopolymers that work in a different solvent condition.

A single-step fabrication of Ag nanoparticles and CVD graphene hybrid nanostructure as SERS substrate

Functionalization and modification of chemical vapor deposition (CVD) growth graphene are crucial to develop new surface-enhanced Raman scattering (SERS) substrate for practical applications. In this study, a hybrid nanostructure of AgNPs@G was designed considering taking advantage of both the electromagnetic enhancement mechanism (EM) and chemical enhancement mechanism (CM) thanks to AgNPs and CVD growth graphene via a single-step fabrication. The size distribution of AgNPs with a perfect single crystalline structure obtained as 2–10 nm and uniformly decorated on CVD graphene surface. The excellent integration of AgNPs and graphene has been confirmed by TEM and XPS studies. The SERS activity of the fabricated AgNPs@G nanocomposite has been examined using Rhodamine 6G (R6G) as a probe molecule with different concentrations. The value of enhancement factor (EF) calculated as 7.2 × 104 suggests that the AgNPs@G nanostructure substrates have perfect SERS properties. The results in this paper demonstrate that the fabricated hybrid nanostructure AgNPs@G can be promising SERS substrate in many practical applications.

Recyclable Fe3O4@C nanocomposite as potential adsorbent for a wide range of organic dyes and simulated hospital effluents

Abstract The present work reported the utilization of Fe3O4@C nanocomposite for removing a series of six organic dyes from aqueous solutions and dealing with simulated hospital effluents. Single-step fabrication of magnetic Fe3O4@C nanocomposite was facilely performed at 500 °C. This material was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Core–shell Fe3O4 NPs ( ∼ 40 nm in average size) were dispersed well and encapsulated by ultrathin carbon coatings with the thickness of 4–5 nm. Fe3O4@C nanocomposite owned surface functional groups important for dyes adsorption. The adsorption results showed that maximum adsorption capacity values of organic dyes on Fe3O4@C obeyed an order as follows: methyl orange (38.03 mg/g) rhodamine B (87.32 mg/g) methylene blue (95.61 mg/g) methyl red (153.1 mg/g) congo red (165.3 mg/g) crystal violet (181.6 mg/g). Two simulated hospital effluents could also be treated from 63.6–84.5% using this nanocomposite. In addition, Fe3O4@C could be reused up to 5 cycles without considerable decrease in uptake capacity.

Waveguide asymmetric long-period grating couplers as refractive index sensors.

A highly sensitive integrated photonic transducer is designed by utilizing asymmetric long-period gratings on a silicon waveguide. These gratings are formed by periodic perturbation of the waveguide width, leading to coupling between the fundamental mode and the 1st order asymmetric leaky mode. The coupled modes are studied via finite-element and finite-difference time-domain methods. Only a single fabrication step is required to realize this novel design. The device is utilized as a refractive index sensor in liquid, yielding a sensitivity of 5078 nm/RIU. The design is a unique combination of being highly sensitive, easily fabricated and highly compact.

Single-step fabrication of single-junction c-Si nano-structured solar cells by optimization of plasma etching parameters

The production cost of photovoltaic solar cells could be reduced by minimizing the number of fabrication steps, e.g., eliminating separate stages of assembling p-layer, n-layer and anti-reflection coating layer. The uniqueness of the present work remains in the single step growth of the n-layer and the simultaneous anti-reflection coating layer via plasma etching of the p-type crystalline silicon (p–c-Si) wafers by low pressure inductively coupled plasma (ICP) CVD system. Chemical and physical etching of the p–c-Si wafer by high density of atomic H and ionic Ar/H species in the (Ar + H2) plasma create surface-roughness that introduce reduced surface reflectance. Further, ejection of Si moieties from the wafer surface produces SiHX (x = 1–4) radicals in the plasma, which in turn instigate re-deposition at the dangling c-Si bond sites and produce variety of silicon nanostructures (Si-NSs). The etching and sequential redeposition effects occur differently on varying gas ratio of Ar/H2, changing plasma pressure and etching temperature. At optimized low pressure (∼100 mTorr) in the plasma crystalline silicon nano-pillar like structures of uniform diameter, length and alignment are produced, from which multiple internal reflections result efficient light trapping and a significantly low reflection loss. Further, the plasma deposited Si nanostructures on the etched p-type c-Si wafer surface changes to n-type in electronic configuration, grown via p-to-n type conductivity conversation (PTNCC) process, initiated by alteration in BH1 bonds to BH2 and/or BH3 configurations. The p-n junction solar cells spontaneously grown via PTNCC mechanism demonstrates a proof-of-concept conversion efficiency, η ∼4.22%, using ITO layer at the front and silver (Ag) paste as the back electrodes.

Fabrication of nickel-yttria stabilized zirconia 3D micro-pattern by atmospheric plasma spray as a dual-functional electrocatalyst for overall water splitting applications in alkaline medium

Identification of active and stable dual-functional electrocatalyst is a key obstacle for producing clean hydrogen fuel. Herein, we report a single-step fabrication of nickel-yttria stabilized zirconia (Ni-YSZ) 3D micro-pattern through atmospheric plasma spray as a dual-functional electrocatalyst for overall water splitting. This 3D micro-pattern strategy improves the mass diffusion pathway and active surface area, resulting in good electrocatalytic activity towards oxygen and hydrogen evolution reactions (OER and HER). Although YSZ alone shows little catalytic activity, Ni decorations enhances the activity towards OER and HER in alkaline solution. Using Ni-YSZ as a dual-functional electrocatalyst, it reaches a current density of 10 mA cm−2 at the potential of 1.70 V, 1.65 V, and 1.67 V after 0 h, 100 h, and 200 h of durability tests. Besides, electrochemical impedance spectroscopy (EIS) spectra analyzed by genetic programming is monitoring the resistance contributed by several relaxations and provides the information about its changes with durability tests and Ni contents. This study opens a new strategy to enhance the water-splitting performance and to analyze the EIS data of electrocatalytic systems.

Single-step fabrication of ZnO microflower thin films for highly efficient and reusable photocatalytic activity

Zinc oxide microflower thin films were deposited in a single-step process using cost-effective ultrasonic spray pyrolysis technique. Different molarity of precursor solution was used to grow the films. X-ray diffraction and Raman spectroscopy reveal the wurtzite structure of ZnO. Scanning electron microscope images showed the microflower morphology which has a better surface to volume ratio. Defects such as O interstitial and Zn vacancy were identified in these thin films with the help of photoluminescence (PL) spectroscopy. The contact angle of the films was found to decrease with increase in molarity of the precursor. Photocatalytic activity of three different molar samples (0.05, 0.1 and 0.15 M) of ZnO were studied for methylene blue (MB) degradation and 0.15 M film demonstrated better degradation efficiency under UV–Vis light. Further degradation studies were performed on this film under exposure to natural sunlight. 90% degradation of the dye was observed in both the conditions upon exposure of 3.5 h. Effect of defects, molarity, bandgap and contact angle of ZnO on the photocatalytic performance is discussed. Repeatability studies performed under both UV–Vis and natural sunlight exposures showed only a minor deviation of 1% from the initial degradation efficiency.

Low-Cost Ultrawideband High-Gain Compact Resonant Cavity Antenna

A 3-D printed planar permittivity-gradient superstrate (PGS) is used to improve the directive radiation characteristics of a waveguide-fed compact resonant cavity antenna (CRCA). Far-field directivity of classical uniform superstrate-based RCAs is limited due to nonuniform aperture phase distribution caused by even transmission through the superstrate. Transverse PGS has been used here to remarkably improve aperture phase distribution and hence directive radiation performance of RCAs. Furthermore, the PGS was rapidly prototyped in one hour and 43 min using a low-cost acrylo-butadiene styrene (ABS) filament without using traditional multistep milling and machining. Single step fabrication was performed and effective dielectric constant of the ABS was varied through controlled infill percentage in different regions of the PGS. Measurements of a prototype indicate unrivaled results, from a smaller footprint, which includes peak directivity of 16.048 dB, 3 dB directivity bandwidth of 49.65% and sidelobe levels lower than -10.4 dB throughout the operating frequency band. The 3-D printed PGS thus outperforms all previously reported superstrates, for RCAs, by demonstrating similar radiation performance with an equivalent material cost of only 0.41 USD.

Ultra-simplified Single-Step Fabrication of Microstructured Optical Fiber

Manufacturing optical fibers with a microstructured cross-section relies on the production of a fiber preform in a multiple-stage procedure, and drawing of the preform to fiber. These processes encompass the use of several dedicated and sophisticated equipment, including a fiber drawing tower. Here we demonstrate the use of a commercial table-top low-cost filament extruder to produce optical fibers with complex microstructure in a single step - from the pellets of the optical material directly to the final fiber. The process does not include the use of an optical fiber drawing tower and is time, electrical power, and floor space efficient. Different fiber geometries (hexagonal-lattice solid core, suspended core and hollow core) were successfully fabricated and their geometries evaluated. Air guidance in a wavelength range where the fiber material is opaque was shown in the hollow core fiber.

Single-step fabrication and work function engineering of Langmuir-Blodgett assembled few-layer graphene films with Li and Au salts

To implement large-area solution-processed graphene films in low-cost transparent conductor applications, it is necessary to have the control over the work function (WF) of the film. In this study we demonstrate a straightforward single-step chemical approach for modulating the work function of graphene films. In our approach, chemical doping of the film is introduced at the moment of its formation. The films are self-assembled from liquid-phase exfoliated few-layer graphene sheet dispersions by Langmuir-Blodgett technique at the water-air interfaces. To achieve a single-step chemical doping, metal standard solutions are introduced instead of water. Li standard solutions (LiCl, LiNO3, Li2CO3) were used as n-dopant, and gold standard solution, H(AuCl4), as p-dopant. Li based salts decrease the work function, while Au based salts increase the work function of the entire film. The maximal doping in both directions yields a significant range of around 0.7 eV for the work function modulation. In all cases when Li-based salts are introduced, electrical properties of the film deteriorate. Further, lithium nitrate (LiNO3) was selected as the best choice for n-type doping since it provides the largest work function modulation (by 400 meV), and the least influence on the electrical properties of the film.

Single-step manufacturing of hierarchical dielectric metalens in the visible

Metalenses have shown a number of promising functionalities that are comparable with conventional refractive lenses. However, current metalenses are still far from commercialization due to the formidable fabrication costs. Here, we demonstrate a low-cost dielectric metalens that works in the visible spectrum. The material of the metalens consists of a matrix-inclusion composite in which a hierarchy satisfies two requirements for the single-step fabrication; a high refractive index and a pattern-transfer capability. We use a UV-curable resin as a matrix to enable direct pattern replication by the composite, and titanium dioxide nanoparticles as inclusions to increase the refractive index of the composite. Therefore, such a dielectric metalens can be fabricated with a single step of UV nanoimprint lithography. An experimental demonstration of the nanoparticle composite-based metalens validates the feasibility of our approach and capability for future applications. Our method allows rapid replication of metalenses repeatedly and thereby provides an advance toward the use of metalenses on a commercial scale.

Single-step fabrication of catechol-ε-poly-L-lysine antimicrobial paint that prevents superbug infection and promotes osteoconductivity of titanium implants

Prevention of infection and promotion of osteoconduction are the key factors to achieve long-term success in orthopaedic implants. In this work, an effective antimicrobial and osteoconductive coating is facilely prepared by the cross-linking of ε-poly-L-lysine (EPL) and catechol (abbreviated as EPLC) via a one-step mussel-inspired chemistry. A series of EPLC paints were prepared by catechol (15 mM) and varying concentrations of EPL (30, 40, and 50 mM) and named as EPLC1, EPLC2, and EPLC3. The coatings were easy to paint on implants. EPLC3 with the highest EPL concentration exhibited the most potent antimicrobial activity (greater than 99.99%) against both Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive “superbug” methicillin-resistant Staphylococcus aureus (MRSA), and inhibited the biofilm formation of MRSA up to one week. Furthermore, the EPLC3 painted Ti implant was capable of reducing more than 3-log bacterial burden in a rodent subcutaneous infection model infected by MRSA. More interestingly, EPLC3 coating increased the osteoconductivity of Ti surfaces by promoting mouse pre-osteoblast MC3T3-E1 adhesion and proliferation. And the EPLC3 painted Ti surfaces could induce hydroxyapatite (HAp) formation after incubation in simulating human body fluids (SBF) within two weeks. Overall, the mussel-inspired EPLC paint can be easily applied to orthopaedic implants, and endowed Ti with antimicrobial activity and promoted its osteoconductivity, which will benefit the long-term success of Ti implants.

Fabrication of a microfluidic device by using two-photon lithography on a positive photoresist

Organ-on-chip (OoC) devices are increasingly used for biomedical research and to speed up the process of bringing a medicinal drug from the lab to the market. The technology also addresses ethical issues linked to animal testing as it offers a reduction in animal experiments through its possibility to mimic the environment in the human body. Hence, it produces more relevant results than plain cell-culture experiments, while still sharing the possibility of high-throughput testing by simultaneously operating many devices in parallel. The main components of an OoC device are microfluidic channels and porous membranes. Current chips are often assembled from several parts. In the development phase a small change in design will cause a delay in the research because a new prototype has to be built again step-by-step. This research addresses this problem by targeting the fabrication of a microfluidic device in a single lithography and development step. A device consisting of two crossed channels at different heights separated by a membrane was chosen. The manufacturing method used was two-photon lithography (TPL) on positive photoresist AZ 4562. TPL exploits the fact that two-photon absorption non-linearly depends on the light intensity. The required intensity is only achieved in a small volume around the focal point, called the voxel. By positioning and moving this voxel inside the resist, 3D manufacturing is possible. Therefore the technique can be used for the single step fabrication of a closed channel. By vertically moving the voxel through the resist, pores can be manufactured. In literature an ellipsoidal voxel shape is assumed, leading to the assumption that the maximum voxel, and therefore pore diameter is found at the focal plane, i.e. at z = 0. However, this research shows that the voxel may also have an hourglass-shape for a high enough laser intensity. In this case the maximum voxel diameter is found at a distance z from the focal plane. For the production of pores, therefore the maximum voxel diameter instead of the diameter at the focal plane has to be taken into account. The smallest pores produced measured 250 nm - 290 nm. AZ 4562 was used as a stamp and a mold for the manufacturing of 3D topographical features on a PDMS surface. Finally the microfluidic device was successfully produced in a layer of 50 µm thick resist. The channel width was 100 µm and the height was 10 µm. The channels were separated by 10 µm in height. The sizes of the input and output holes were adapted to the diameter of the smallest available blunt needle, which is 210 µm.

Single step fabrication by spray forming of large volume Al-based composites reinforced with quasicrystals

Recently it was shown that the Al–Cu–Fe–Cr system can form a microstructure consisting mainly of quasicrystalline and α-Al phases by arc-melting and subsequent annealing of an appropriate composition. In the present work we demonstrate that it is possible to fabricate a large volume of this composite directly from the liquid phase by spray forming an Al85Cu6Fe3Cr6 (%at) alloy. The overspray powder and an arc-melted sample were also analyzed. Tribological properties of the Al-based composite reinforced with quasicrystals was evaluated by pin-on-disk tests, which demonstrated to be superior than an Al–Si alloy, A380, used in this work as a comparison material.