Single-step Fabrication Research Articles

Single-Step Fabrication and Characterization of Nanoscale Cu Thinfilms for Optoelectronic Applications

Nanostructured materials with optical transmittance with sufficient electrical conductivity are feasible for the transparent electrical devices and optoelectronic applications. Copper (Cu) possesses inherent superior electrical conductivity. Cu thin films on glass substrates provide the basic design understanding of the transparent electrodes for humidity sensors and solar cells applications. To understand the fundamental fabrication and electrical properties, a single-step facile fabrication approach was applied for Cu nanofilms through the DC sputtering method. Correlation of thickness of Cu nanofilms with optical and electrical properties was established. Parameters such as current, voltage, vacuum pressure, and time of coating were varied to develop different thickness of metal coating. Under optimized conditions of 10−1 torr vacuum, 1.45 KV voltage, and 4–6 min coating time, a conductive path is successfully established. A 1 min coated sample demonstrated resistance of 4000 ohm and conductance of a 6 min coated sample was raised to 56 m-mho. A higher surge of voltage assisted the production of relatively thick and uniform coatings with the crystallite size of 12 nm. The average coating thickness of 19.8 nm and roughness of 4.5 nm was obtained for a 5 min coated sample through AFM analysis. Further, it was observed that uniform nanostructured coating is essential to establish a mean free path of coated particles.

Anodization of large area Ti: a versatile material for caffeine photodegradation and hydrogen production

Facile, single-step, and scalable fabrication of large-area (∼20 cm2) TiO2 nanostructures (TNS) with promising photocatalytic activity and hydrogen production rate under UVA light was carried out via electrochemical anodization.

Single Step Fabrication of Fe-Single Walled Carbon Nanotube Film from Ferrocene as a Conductive-Electrocatalyst Interlayer in Lithium-Sulfur Batteries

Single Step Fabrication of Fe-Single Walled Carbon Nanotube Film from Ferrocene as a Conductive-Electrocatalyst Interlayer in Lithium-Sulfur Batteries

Stress induced self-rollable smart-stent-based U-health platform for in-stent restenosis monitoring.

To date, several smart stents have been proposed to continuously detect biological cues, which is essential for tracking patients' critical vital signs and therapy. However, the proposed smart stent fabrication techniques rely on conventional laser micro-cutting or 3D printing technologies. The sensors are then integrated into the stent structure using an adhesive, conductive epoxy, or laser micro-welding process. The sensor packaging method using additional fabrication processes can cause electrical noise, and there is a possibility of sensor detachment from the sent structure after implantation, which may pose a significant risk to patients. Herein, we are demonstrating for the first time a single-step fabrication method to develop a smart stent with an integrated sensor for detecting in-stent restenosis and assessing the functional dynamics of the heart. The smart stent is fabricated using a microelectromechanical system (MEMS)-based micromachining technology. The proposed smart stent can detect biological cues without additional power and wirelessly transmit the signal to the network analyzer. The cytocompatibility of the smart stent is confirmed through a cytotoxicity test by monitoring the cell growth, proliferation, and viability of the cultured cardiomyocytes. The capacitance of the smart stent exhibits an excellent linear relationship with the applied pressure. The exceptional sensitivity of the pressure sensor enabled the proposed smart stent to detect biological cues during in vivo analysis. The preliminary findings confirmed the proposed smart stent's higher level of structural integrity, durability and repeatability. Finally, the practical feasibility of the smart stent is demonstrated by monitoring diastole and systole at various beat rates using a phantom. The results of the phantom study showed a similar pattern to the human model, indicating the potential use of the proposed multifunctional smart stent for real-time applications.

Volumetric additive manufacturing of shape memory polymers

Shape memory polymers (SMPs) capable of recovering from a deformed state through heating were 3D printed using volumetric additive manufacturing, which enabled the layerless, single-step fabrication of self-standing tripod and actuating gripper structures.

Rapid Prototyping of Organ-on-a-Chip Devices Using Maskless Photolithography.

Organ-on-a-chip (OoC) and microfluidic devices are conventionally produced using microfabrication procedures that require cleanrooms, silicon wafers, and photomasks. The prototyping stage often requires multiple iterations of design steps. A simplified prototyping process could therefore offer major advantages. Here, we describe a rapid and cleanroom-free microfabrication method using maskless photolithography. The approach utilizes a commercial digital micromirror device (DMD)-based setup using 375 nm UV light for backside exposure of an epoxy-based negative photoresist (SU-8) on glass coverslips. We show that microstructures of various geometries and dimensions, microgrooves, and microchannels of different heights can be fabricated. New SU-8 molds and soft lithography-based polydimethylsiloxane (PDMS) chips can thus be produced within hours. We further show that backside UV exposure and grayscale photolithography allow structures of different heights or structures with height gradients to be developed using a single-step fabrication process. Using this approach: (1) digital photomasks can be designed, projected, and quickly adjusted if needed; and (2) SU-8 molds can be fabricated without cleanroom availability, which in turn (3) reduces microfabrication time and costs and (4) expedites prototyping of new OoC devices.

Single-step fabrication of highly stable amorphous TiO2 nanotubes arrays (am-TNTA) for stimulating gas-phase photoreduction of CO2 to methane

This study investigates the facile fabrication of interfacial defects assisted amorphous TiO2 nanotubes arrays (am-TNTA) for promoting gas-phase CO2 photoreduction to methane. The am-TNTA catalyst was fabricated via a one-step synthesis, without heat treatment, by anodization of Titanium in Ethylene glycol-based electrolyte in a shorter anodizing time. The samples presented a TiO2 nanostructured array with a nanotubular diameter of 100 ± 10 nm, a wall thickness of 26 ± 5 nm, and length of 3.7 ± 0.3 μm, resulting in a specific surface of 0.75 m2 g. The am-TNTA presented prolonged chemical stability, a high exposed surface area, and a large number of surface traps that can reduce the recombination of the charge carriers. The am-TNTA showed promising photoactivity when tested in the CO2 reduction reaction with water under UV irradiation with a methane production rate of 14.0 μmol gcat−1 h−1 for a pure TiO2 material without any modification procedure. This enhanced photocatalytic activity can be explained in terms of surface defects of the amorphous structure, mainly OH groups that can act as electron traps for increasing the electron lifetime. The CO2 interacts directly with those traps, forming carbonate species, which favors the catalytic conversion to methane. The am-TNTA also exhibited a high stability during six reaction cycles. The photocatalytic activity, the significantly reduced time for synthesis, and high stability for continuous CH4 production make this nanomaterial a potential candidate for a sustainable CO2 reduction process and can be employed for other energy applications.

First report on graphene oxide free, ultrafast fabrication of reduced graphene oxide on paper via visible light laser irradiation

Conventionally, highly conductive reduced graphene oxide (rGO) is synthesized by chemical reduction of graphene oxide (GO) solution using strong toxic reducing agents. However, GO itself is synthesized using strong acids and oxidants, with repetitive cleaning and laborious steps. To overcome such challenges, this work demonstrates a novel solution to the age-old rGO synthesis route by proposing a GO free, single-step, and ultrafast rGO fabrication on paper via blue light laser irradiation, named LIrGO, for direct use in papertronic applications. Such LIrGO was thoroughly characterized, and the results were completely consistent with the conventional approach. Without any post-processing, like thermal heating or cleaning, a high carbon to oxygen ratio (7.1), narrow microfibres with mesoporous granular linked morphological structure, good electrical conductivity, and minimal sheet resistance of about 23 Ω sq−1 were obtained within few minutes based on design dimensions. With such LIrGO, various circuits and complex designs can be printed directly on paper, leading to realize environmentally friendly papertronic devices. Herein, a paper-based capacitive touch sensor was validated for excellent touch response. Further, the resulting LIrGO on paper can be hand-scraped to create composite materials for other applications. The scrapped LIrGO was leveraged to investigate the absorption capacities of PVA/rGO/Sponge and rGO/Sponge coatings over a few cycles for selective separation of oil from an oil-water emulsion. The proposed method is a beginning for a new era of rGO fabrication at a single-step avoiding all the toxic chemical routes.

Evaluation of Mo(1-x)W x s Alloy Fabricated By Combinatorial Film Deposition

Recently, research on two-dimensional layered materials is progressing rapidly. Transition metal dichalcogenides (TMDs) show bandgap, which is bringing high expectations for a variety of applications such as electronics and optoelectronics. Mo(1-x)W x S2 is an alloy semiconductor of MoS2 and WS2, two of the most representative TMD materials, and it is possible to modulate physical properties such as optical characteristics by changing the W concentration x [1-3]. In this study, we performed a combinatorial film deposition in which the W concentration changes from 0 to 100% within one sample using RF magnetron sputtering method [4]. Since the combinatorial film deposition can form a continuous compositional gradient in the sample, continuous modulation of physical properties is expected. There have been different reports on the fabrication of the alloy with chemical vapor transport followed by exfoliation, or chemical vapor deposition [5]. However, in this study single-step fabrication of the alloy with sputtering was achieved. The physical properties such as the band structure of the fabricated sample were investigated.MoS2 and WS2 targets were used for the fabrication of the alloy. The substrate temperature was 300 °C, Ar pressure was 0.3 Pa, and the RF power applied to the MoS2 and WS2 targets were 80 W and 50 W, respectively. The film thickness was adjusted to approximately 100 nm by controlling the deposition time. Surface oxidized Si was used as the substrate. A schematic diagram of the sample is shown in Fig. 1. Using X-ray photoelectron spectroscopy (XPS) for quantitative analysis of the sample, the W concentration x and the sulfur to metal ratio S / (Mo + W) were calculated by determining the peak area ratios of Mo 3d, W 4f, and S 2p. In addition, spectroscopic ellipsometry analysis was carried out to calculate the bandgap for each concentration region.Figure 2 shows the in-plane composition distribution determined by line measurement with XPS. From Fig. 2, it can be seen that the W concentration changes almost linearly, and the stoichiometric ratio was achieved. The linearly changing composition gradient allowed us to accurately select the composition of the alloy for the other evaluation. The bandgap with respect to W concentration using spectroscopic ellipsometry is shown in Fig. 3. It was confirmed that the band gap can be controlled by changing the W concentration. In addition, the change was accompanied by bowing which is a unique behavior often observed in the alloy materials. Figure 4 shows the band alignment of different W concentration x determined by using XPS and spectroscopic ellipsometry. From this result, it was found that the band structure can be controlled according to the requirements of the devices. We believe that this opens new opportunity for the TMD in electronic device applications.This work was partly supported by JST CREST Number JPMJCR16F4, Japan. This work was also partly supported by JSPS KAKENHI Grant Number 18J22879.REFERENCES Y. Chen, J. Xi, D. O. Dumcenco, Z. Liu, K. Suenaga, D. Wang, Z. Shuai, Y. S. Huang, and L. Xie, ACS Nano 7, 4610 (2013).H. -P. Komsa, and A. V. Krasheninnikov, J. Phys. Chem. Lett. 3, 3652 ( 2012).P. M. Jahani, S. T., H. Beitollahi, S. Mohammadi, and M. R. Aflatoonian, Research on Chemical Intermediates 46, 837(2020).S. Noda, H. Sugime, T. Osawa, Y. Tsuji, S. Chiashi, Y. Murakami, and S. Maruyama. Carbon 44, 8 (2006).Z. Wang, P. Liu, Y. Ito, S. Ning, Y. Tan, T. Fujita, A. Hirata, and M. Chen. Sci. Reports 6, 21536 (2016). Figure 1

Controlled synthesis of luminescent ZnS nanosheets with high piezoelectric performance for designing mechanical energy harvesting device

For the first time, single-step fabrication of two-dimensional nanosheets of zinc sulfide (ZnS) was achieved employing flexible aluminum (Al) foil substrate using hydrothermal technique at 140 °C for ∼4 h. Indium doped Tin Oxide (ITO) coated on PET (Polyethylene Terephthalate) substrate and ZnS deposited Al foil as a top and bottom electrodes were used to fabricate a piezoelectric device. To generate an electric potential, the top ITO electrode was tapped on the ZnS nanosheets. The open-circuit voltage, VOC of ∼400 mV was obtained and analyzed for ZnS nanosheets based nanogenerator with gentle finger taping. However, the highest output for the single nanogenerator was found to be ∼600 mV by applying toe pressure. Additionally, switching polarity and superposition experiments were utilized to confirm the nanogenerator's performance, with the findings confirming piezo-electric voltage output. This study investigates the new potential for a ZnS-based high-efficient energy harvester that can scavenge biomechanical energy for next-generation flexible self-powered electronics devices as well as a good replacement for ZnO nanosheets in 2D nanostructured based nanogenerator devices due to its simple single-step production process, low cost, and high output gain.

Single-step fabrication of a teicoplanin functionalized organic-silica hybrid monolith for enantioseparation by nano-liquid chromatography

A novel teicoplanin functionalized organic-silica hybrid chiral monolithic column was prepared by a facile single-step approach. The conditions for the preparation of the organic-silica hybrid chiral monolithic column were systematically optimized, including the amount of poly (ethylene glycol) (PEG) and urea, the tetramethyl orthosilicate (TMOS)/3-(trimethoxysilyl)-propylmethacrylate (γ-MAPS) ratio (v/v), the content of teicoplanin-2-isocyanatoethyl methacrylate (Tei-ICNEML) monomer, and the reaction temperature and time. The optimum column exhibited satisfactory efficiency, permeability and stability. In order to obtain satisfactory enantioseparation performance, reversed phase (RPM) and polar organic phase (POM) modes were employed, and different experimental conditions were optimized, such as buffer concentration and pH, amount of the organic solvent, concentration and ratio of TEA/HAc, and MeOH/ACN ratio. The stability of the Tei-ICNEML organic-silica hybrid monolithic column was also investigated in both POM and RPM separation modes. Then, this novel monolithic column was successfully applied to achieve the enantioseparation of amino alcohols, N-derivatized amino acids and mandelic acids. 15 out of 20 amino alcohols were baseline separated with good column efficiency in the POM mode, and 3 out of 5 mandelic acids and 5 out of 6 N-derivatized amino acids were baseline separated in the RPM mode.

Micro-indented-mechanically-engineered Ni-Fe-Mo-Cu alloying electrocatalyst for oxygen evolution reaction: A cost-effective approach for green hydrogen production

Hydrogen is the next-generation clean and ecofriendly alternative energy source. Its generation through water splitting is promising for sustainable production. The advancement of highly effective, stable, and profitable materials are the key challenges in catalyst design. In this direction, a novel single-step fabrication strategy employing micro-indented-mechanically-engineered (MIME) multinary (Ni-Fe-Mo-Cu) bare metallic material is an intriguing attempt to develop a highly efficient electrocatalytic oxygen evolution reaction (OER) at lower overpotential. This novel idea is based on applying compressive load through a rolling mill to generate micro-indents that act as active sites for the hydroxyl ions for accelerating OER. The Linear sweep voltammetry (LSV) curves showed 10 mA cm−2 could be generated employing the MIME electrode of 1000 N load at a lower overpotential. Electrochemical Impedance Spectroscopy (EIS) revealed that the lowest polarization resistance (Rp) was obtained at the same load. The electrocatalytic activity of the electrode was sustained by the formation of the porous oxide film which eventually improved the overall electrochemical surface-area of the electroactive film composed of respective alloying elements confirmed by comprehensive X-ray photoelectron spectroscopy (XPS) analysis.

Direct (3+1)D laser writing of graded-index optical elements

We propose single-step additive fabrication of graded-index optical elements by introducing the light exposure as the additional dimension to three-dimensional (3D) laser writing, hence (3 + 1)D writing. We use a commercial printer and photoresist to realize the proposed single-step fabrication method that can be swiftly adopted for research and engineering. After presenting the characterization of the graded-index profiles via basic structures, we demonstrate two different optical devices: volume holograms that are superimposed using angular and peristrophic multiplexing, and optical waveguides with well-defined refractive index profiles. In the latter, we precisely control the propagating modes via tuning the (3 + 1)D-printed waveguide parameters and report step-index and graded-index core–cladding transitions.

A spontaneous one-step fabrication of slippery gel coatings

Lubricant infused surfaces (LIS) have omniphobic repulsion towards most liquids and have applications in various fields. The initial subtractive fabrication methods were multiphase, complex, and substrate limited, requiring specific surface topologies functionalised with fluorosilanes before being infused with low surface tension lubricants. Numerous additive approaches have been developed to overcome these limitations, including chemical, nanoparticle, and polymeric layers. While effective, these coatings still require complex or multi-step syntheses with expensive compounds and substrate limiting fabrication conditions. This paper will present a single-step fabrication methodology for an omniphobic slippery gel coating, predicated on spontaneous urea cross-linking between branched polyethyleneimine and isocyanate bi-terminated perfluoropolyether, with a hydroxy bi-terminated PFPE as both solvent and lubricant. The resulting coatings showed the presence of fluorine and carbon chemistries, and the formation and size of raised island topologies (from the nano – micro range) correlating to the molar ratio of the coating solutions. Extensive examination of the contact and sliding angles of water, canola oil, and n-hexane showed that coatings retained omniphobic properties after numerous lubricant layer removals via pure ethanol. The rapid and facile methodology used to produce the fluorogel coatings allows for an easy transition into larger-scale industrial applications.

Single-step-fabricated disordered metasurfaces for enhanced light extraction from LEDs

While total internal reflection (TIR) lays the foundation for many important applications, foremost fibre optics that revolutionised information technologies, it is undesirable in some other applications such as light-emitting diodes (LEDs), which are a backbone for energy-efficient light sources. In the case of LEDs, TIR prevents photons from escaping the constituent high-index materials. Advances in material science have led to good efficiencies in generating photons from electron–hole pairs, making light extraction the bottleneck of the overall efficiency of LEDs. In recent years, the extraction efficiency has been improved, using nanostructures at the semiconductor/air interface that outcouple trapped photons to the outside continuum. However, the design of geometrical features for light extraction with sizes comparable to or smaller than the optical wavelength always requires sophisticated and time-consuming fabrication, which causes a gap between lab demonstration and industrial-level applications. Inspired by lightning bugs, we propose and realise a disordered metasurface for light extraction throughout the visible spectrum, achieved with single-step fabrication. By applying such a cost-effective light extraction layer, we improve the external quantum efficiency by a factor of 1.65 for commercialised GaN LEDs, demonstrating a substantial potential for global energy-saving and sustainability.

Rapid Inkjet-Printed Miniaturized Interdigitated Electrodes for Electrochemical Sensing of Nitrite and Taste Stimuli.

This paper reports on single step and rapid fabrication of interdigitated electrodes (IDEs) using an inkjet printing-based approach. A commercial inkjet-printed circuit board (PCB) printer was used to fabricate the IDEs on a glass substrate. The inkjet printer was optimized for printing IDEs on a glass substrate using a carbon ink with a specified viscosity. Electrochemical impedance spectroscopy in the frequency range of 1 Hz to 1 MHz was employed for chemical sensing applications using an electrochemical workstation. The IDE sensors demonstrated good nitrite quantification abilities, detecting a low concentration of 1 ppm. Taste simulating chemicals were used to experimentally analyze the ability of the developed sensor to detect and quantify tastes as perceived by humans. The performance of the inkjet-printed IDE sensor was compared with that of the IDEs fabricated using maskless direct laser writing (DLW)-based photolithography. The DLW–photolithography-based fabrication approach produces IDE sensors with excellent geometric tolerances and better sensing performance. However, inkjet printing provides IDE sensors at a fraction of the cost and time. The inkjet printing-based IDE sensor, fabricated in under 2 min and costing less than USD 0.3, can be adapted as a suitable IDE sensor with rapid and scalable fabrication process capabilities.

Wavelength and decay time tuning of intraband transitions in low spatial frequency laser-induced periodic surface structures

We present the study of the alteration of wavelength and decay time of intraband transitions in the laser-induced periodic surface structures (LIPSS) of silver formed by varying the incident laser peak fluence. The studies are performed using a femtosecond laser (λ0 = 800 nm) based ultrafast transient absorption spectroscopy (UFTS)setup. Using the same laser, an array (~2 mm size) of laser-induced periodic surface structures were obtained in a single-step fabrication process in the open air without translating the sample. Each unit cell of the array comprises low spatial frequency LIPSS (LSFL) near the center with nanoparticles/clusters around the edges. As obtained from 2D Fast Fourier Transform, the overall periodicity(Λ) of LSFL is within 0.714λ0–0.723λ0 range. The nanoparticles/clusters show a random size distribution that varies from 50 nm to 300 nm. In UFTS measurement, the LIPSS was excited by a 3.3 eV laser. The SPP/SPR dip in the data is an indication of intraband transition or hot electron generation. The effect of change in structuring due to varying laser fluence on these intraband transitions is also analyzed. It is observed that there is a non-linear redshift (~16 nm) in the SPR peak wavelength with a significant enhancement in the relaxation times of the hot electrons due to localized annealing of shallow defects. Therefore, a large tunability in wavelength of SPP/SPR and lifetime of hot electrons was achieved by varying the laser fluence. The study highlights the suitability of LIPSS in applications requiring efficient energy transfer, enhanced photocatalytic action, and tunable sensors.

Photonic implementation of artificial synapses in ultrafast laser inscribed waveguides in chalcogenide glass

Simple and direct prototyping methods are ideal for large-scale delivery of cognitive photonic hardware. Here, we choose ultrafast laser writing as a direct fabrication technique to later demonstrate all-optical synaptic-like performance along the laser-written waveguides in a chalcogenide glass. Neuronal communication protocols, such as excitatory and inhibitory responses, temporal summations, and spike-timing-dependent plasticity, are shown in the glass chip. This work manifests the potential for large-scale delivery of fully integrated photonic chips based on cognitive principles by single-step fabrication procedures.

Pulsed laser deposition of plasmonic structures in air by irradiation through the substrate

This work presents results from a method for single step fabrication of noble metal nanostructures in air that express plasmonic properties. A special configuration of the laser irradiation through the substrate is applied. Due to the interaction of the deposited material with the incident laser radiation, the resulting structure could be a dense nanoparticle monolayer instead of three-dimensional structure, which is usually obtained at pulsed laser deposition in air. The proposed geometry of irradiation is characterized by several key parameters that are defined and their influence on the properties of the fabricated structures is studied. The change of the processing conditions may result in significant change of the optical properties of the deposited structures. This effect is more expressed in the case of silver. The deposition of gold at the presented method leads to a saturation of the amount of the deposited material, and respectively to constant optical properties with the increase of the deposition time at fixed other parameters. Conditions where formation of a monolayer of well-defined separated nanoparticles are also presented. It is demonstrated that using this method composite gold/silver structures with tunable optical properties can be obtained. On a basis of numerical calculations, the optical properties of the obtained structure and the temperature evolution of the formed material are obtained. These data are used to explain the observed dependences and the formation mechanism. The method is simple and can be applied for efficient deposition of plasmonic systems with potential application in the design of different optical and sensor elements.

Electrospray technology as a probe for single step fabrication of glipizide loaded nanocochleates with enhanced bioavailability

Nanocochleates (NCs) are amongst the nanoformulations gaining wide popularity owing to their ability to improve biopharmaceutical performance of drug molecules remarkably. However, biggest drawback of this nanocarrier is that it requires minimum two steps for synthesis which limits its industrial scalability. Considering the same, the present work was designed with an objective to assess suitability of electrospray technique in the preparation of biomaterial based NCs. Glipizide (GPZ) was chosen as a model drug for preparation of NCs. Briefly, GPZ, phosphatidylcholine and cholesterol were dissolved in methanol and co-axially sprayed into a pool of CaCl2 solution. Factorial design (22) approach was used for batch optimization. The optimized batch was evaluated for surface morphology, FTIR, DSC, zeta potential, in-vitro drug release study and in-vivo evaluation in male wistar rats. FESEM images confirmed formation of NCs using electrospray technique. Negative zeta potential (-14.36 ± 0.55 mV) of optimized batch reflected high stability of the sample. GPZ was released in a controlled manner from the optimized GPZNC. In-vivo pharmacokinetic study demonstrated significant increase in Cmax (2-fold) and AUC (3-fold) upon entrapment of GPZ into NCs. Thus, the present work unfolded suitability of electrospray technology toward single step preparation of Phosphatidylcholine and Cholesterol biomaterial based nanocochleates over currently used two step preparation techniques.