Single-step Fabrication Research Articles

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.

Single-step fabrication of microsphere arrays on the surface of flexible materials by direct solidification

The formation of microarrays on the surface of flexible materials has great potential value in fabrication of functional devices such as various kinds of flexible electronic sensors. To fabricate microarrays on the surface of flexible materials, many methods have been proposed, such as nanoimprint lithography technique, single-pulse laser interference and colloidal self-assembly. In our study, we present a simple method to fabricate silica microsphere arrays embedded on the surface of polyurethane film in a single-step. We directly solidified self-assembled microspheres at the air-liquid interface, and obtained polyurethane film embedded with silica microarrays on its surface. Compared with other methods, precise operation and complicated equipment are not required. In addition, we also utilized the fabricated microarrays as a template to fabricate concave microarrays on the surface of other flexible materials.

Formation of partially reversible nanostructures in Ni40Ti60 thin films by focused electron beam irradiation

Background: Micrometer and submicron-scale shape memory devices are typically fabricated by standard lithographic techniques or focused ion beam milling. It was previously shown that submicron-scale structures can be directly formed on metal surfaces by focused electron beam irradiation in a single fabrication step, without resist layers or etching. Aim: Our aim was to apply the method of a focused electron beam irradiation to a surface of a shape memory material to check if the fabricated structures would display any shape memory effects. Approach: Ni40Ti60 thin film, which was obtained by dual magnetron sputtering on a heated Si substrate, was irradiated by a focused electron beam in point mode. After the irradiation, thin film was heated to 100°C and irradiated points were measured by atomic force microscopy both before and after the heating. Results: After heating, the volume of the formed structures decreased by up to 88% due to their partial reversion back to a flat surface. Conclusions: These results present a new method of fabrication for shape memory devices. As only a one-way shape memory effect is achieved in our work, its immediate applications appear to be limited, but we hope that this work will open possibilities for new types of shape memory devices at the nanometer scale.

Recycling papermill waste lignin into recyclable and flowerlike composites for effective oil/water separation

A micrometer-sized porous material with superhydrophobicity surface is produced via one-step synthesis using Kraft lignin, a waste from pulp and paper industry, as the starting material. Non-fluorinated silane precursor is used for lignin modification to avoid the environmental, cost, and toxicity issues arising from fluorinated precursor. The silane-modified lignin has rather rough flower-like surface microstructures formed by closely-packed crater pores of different sizes ranging from nanometers to micrometers. The modified lignin exhibits superhydrophobic property with a water contact angle of 156°. The material can effectively separate immiscible oil/water mixtures with higher than 99% efficiency, and surfactant-stabilized oil/water emulsions with higher than 98% efficiency. The material shows good recyclability and reusability for oil/water mixture and emulsion separation. The silane modification is an attractive route to develop waste lignin into useful materials with potential applications in oil/water separation, which uses a naturally derived and renewable raw material with a single-step fabrication strategy.

Femtosecond Laser Fabrication of Hybrid Metal-Dielectric Structures with Nonlinear Photoluminescence

Fabrication of hybrid micro- and nanostructures with a strong nonlinear response is challenging and represents a great interest due to a wide range of photonic applications. Usually, such structures are produced by quite complicated and time-consuming techniques. This work demonstrates laser-induced hybrid metal-dielectric structures with strong nonlinear properties obtained by a single-step fabrication process. We determine the influence of several incident femtosecond pulses on the Au/Si bi-layer film on produced structure morphology. The created hybrid systems represent isolated nanoparticles with a height of 250–500 nm exceeding the total thickness of the Au-Si bi-layer. It is shown that fabricated hybrid nanostructures demonstrate enhancement of the SHG signal (up to two orders of magnitude) compared to the initial planar sample and a broadband photoluminescence signal (more than 200 nm in width) in the visible spectral region. We establish the correlation between nonlinear signal and phase composition provided by Raman scattering measurements. Such laser-induced structures have significant potential in optical sensing applications and can be used as components for different nanophotonic devices.

Single-Step Fabrication of a Multiscale Porous Catalyst Layer by the Emulsion Template Method for Low Pt-Loaded Proton Exchange Membrane Fuel Cells

Multiscale porosity assures better mass transport for a low Pt-loaded fuel cell; however, achieving a complex pore structure in a simple manner presents a major challenge. In this work, by using the emulsion template method, a multiscale porous catalyst layer with macro- and mesopores was fabricated in a single step. A stable high internal phase emulsion is achieved with catalyst layer components by exploiting a Nafion ionomer as a surfactant. The oil phase of the emulsion catalyst slurry induces the macropores, and the Pt/C and ionomer mixture in the hydrophilic solvent forms a mesoporous framework in the catalyst layer. Scanning electron microscopy and micro X-ray computed tomography confirmed the formation of uniform and well-interconnected macropores. The performance of the low Pt-loaded catalyst layer derived from the emulsion template method considerably improved the mass transport property due to the mitigation of water flooding. The fabrication of an emulsion-based catalyst layer provides an efficient platform to design high-performance low Pt-loaded fuel cells.

Antioxidant, anticancer and enhanced photocatalytic potentials of gold nanoparticles biosynthesized by common reed leaf extract

This research discloses a single step, facile, cost-effective, and eco-friendly fabrication of gold nanoparticles (AuNPs) using the aqueous extract of common reed (Phragmites australis) leaf. Various techniques were employed to characterize the resultant AuNPs such as UV–Vis spectroscopy, high resolution transmission electron microscopy (HRTEM) mapping, fourier transform infrared (FT-IR), Zeta potential, X-ray diffraction (XRD), Energy Dispersive X-ray spectroscopy (EDX), and X-ray Photoelectron Spectroscopy (XPS) to confirm the bioformation of AuNPs. The results showed the formation of violet-colored, mainly spherical shaped AuNPs with about 18 nm diameter. The XRD results proved the crystalline structure of AuNPs. Furthermore, P. australis-AuNPs exhibited notable anticancer efficacy with an IC50 equals 129 μg/mL, good quenching for DPPH free radical with a scavenging percentage equals 10.26% and a superior photocatalytic activity as they completely removed methylene blue in just 1 min. The current study also provides an open option for the environmental management of the unwanted biomass of common reed.

Photonic circuits written by femtosecond laser in glass: improved fabrication and recent progress in photonic devices

Integrated photonics is attracting considerable attention and has found many applications in both classical and quantum optics, fulfilling the requirements for the ever-growing complexity in modern optical experiments and big data communication. Femtosecond (fs) laser direct writing (FLDW) is an acknowledged technique for producing waveguides (WGs) in transparent glass that have been used to construct complex integrated photonic devices. FLDW possesses unique features, such as three-dimensional fabrication geometry, rapid prototyping, and single step fabrication, which are important for integrated communication devices and quantum photonic and astrophotonic technologies. To fully take advantage of FLDW, considerable efforts have been made to produce WGs over a large depth with low propagation loss, coupling loss, bend loss, and highly symmetrical mode field. We summarize the improved techniques as well as the mechanisms for writing high-performance WGs with controllable morphology of cross-section, highly symmetrical mode field, low loss, and high processing uniformity and efficiency, and discuss the recent progress of WGs in photonic integrated devices for communication, topological physics, quantum information processing, and astrophotonics. Prospective challenges and future research directions in this field are also pointed out.

Towards high performance flexible planar supercapacitors: In-situ laser scribing doping and reduction of graphene oxide films

A novel, scalable, single-step and low-synthesis temperature fabrication approach is proposed for real-time doping, reduction, and patterning of graphene oxide-based films supported on flexible polyethylene terephthalate (PET) substrate using a CO2 Laser system. Laser reduced graphene oxide (LrGO), nitrogen-doped laser reduced graphene oxide (N-LrGO), and sulfur-nitrogen co-doped laser reduced graphene oxide (SN-LrGO) planar supercapacitors (PSCs) are readily fabricated with the proposed approach. Structural and elemental characterizations prove the successful integration of nitrogen and sulfur atoms into the graphene framework with high contents up to 3.71 at% N and 1.82 at% S, and at a low density of structural defects. An areal capacitance as high as 13.8 mF cm−2 at 10 mV s−1 and a maximum power density of 151.7 mW cm−3 at an energy density of 0.152 mWh cm−3 is achieved by SN-LrGO PSC composed of 10 interdigitated fingers with an excellent retention rate after 2000 charging/discharging cycles at 0.125 mA cm−2. Furthermore, higher operating voltage window and current ratings are easily achieved via series and parallel combinations of SN-LrGO PSCs directly on the same substrate. This manifests the versatility of the proposed approach for producing flexible and high-performance graphene-based electrochemical storage devices.

Laser-etched grooves for rapid fluid delivery for a paper-based chemiresistive biosensor

Paper-based microfluidic devices are an attractive option for developing low-cost, point-of-care diagnostic tools. To incorporate more complex assays into paper, these devices must become more sophisticated, through the sequential delivery of different liquids or reagents without user intervention. Many flow control strategies focus on slowing the fluid down. However, this can lead to increased assay times and sample loss due to evaporation. We report the use of a CO2 laser to create etched grooves on paper to accelerate wicking speeds in paper-based microfluidic devices. We explored different laser settings to determine the optimal configuration. Our findings showed that simply cutting a slit into the paper created the fastest wicking channels. The slit acted as a macro capillary, allowing fluid to bypass the paper and speed it up. Further studies determined an ideal groove pitch of 0.75 mm (spacing in between grooves) for a paper channel. Additional experiments documented how sealing grooved channels with different adhesives can influence wicking. Overall, sealing the channels with tape made them wick faster. However, sealing methods such as lamination had a negative effect on wicking. Laser-etched grooves were successfully used to design a fluid-handling architecture for a chemiresistive paper-based biosensor. The grooves facilitated rapid, sequential delivery of sample and wash buffer. Human serum albumin spiked in phosphate buffer, artificial urine, and artificial saliva was successfully detected at as low as 15 pM. Etching grooves in paper is a simple process that requires no additional materials or chemicals, allowing single-step fabrication of paper-based microfluidic channels.

Absolute and arbitrary orientation of single-molecule shapes

DNA origami is a modular platform for the combination of molecular and colloidal components to create optical, electronic, and biological devices. Integration of such nanoscale devices with microfabricated connectors and circuits is challenging: Large numbers of freely diffusing devices must be fixed at desired locations with desired alignment. We present a DNA origami molecule whose energy landscape on lithographic binding sites has a unique maximum. This property enabled device alignment within 3.2° on silica surfaces. Orientation was absolute (all degrees of freedom were specified) and arbitrary (the orientation of every molecule was independently specified). The use of orientation to optimize device performance was shown by aligning fluorescent emission dipoles within microfabricated optical cavities. Large-scale integration was demonstrated with an array of 3456 DNA origami with 12 distinct orientations that indicated the polarization of excitation light.

Orienting origami binding

DNA Origami Directing self-assembly for devices will require placing nanocomponents not only in the correct position on a surface but also in particular orientations. Gopinath et al. designed an asymmetric DNA origami, a “small moon” shape that binds to lithographically patterned sites on silica to within 3° of a target orientation angle. The authors were able to position and orient a molecular dipole within the resonant mode of an optical cavity. More than 3000 DNA origami were arranged in a single fabrication step in 12 different orientations to create a simple polarimeter. Science , this issue p. [eabd6179][1] [1]: /lookup/doi/10.1126/science.abd6179

Single-step fabrication and environmental applications of activated carbon-containing porous cellulose beads

Activated carbon (AC)-containing porous cellulose beads (ACPBs) with a three-dimensionally interconnected porous structure and high impact strength were prepared in a single step from cellulose acetate and AC via a non-solvent-induced phase separation process at room temperature. The adsorption behavior of the ACPBs was evaluated using toluidine blue (TB) dye as a model adsorbate. The effects of initial dye concentration and contact time on the adsorption kinetics and isotherms of ACPBs were studied. The adsorption of TB by the ACPBs followed pseudo-second-order kinetics and could be expressed by the Langmuir adsorption isotherm model. ACPB adsorbed 119.1 mg/g of TB at an initial TB concentration of 101.0 mg/L and the Langmuir equation predicted that the maximum adsorption capacity of ACPBs for TB was 123.5 mg/g. ACPBs could retain original shape and around 85% of their adsorption capacity after three times recycle. Furthermore, ACPBs efficiently removed malodorous gases from gas mixtures, indicating potential for environmental applications including toxic dye and gas elimination.

Simultaneous crosslinking induces macroscopically phase-separated microgel from a homogeneous mixture of multiple polymers

This paper reports a unique phase separation behavior, a simultaneous-crosslinking-driven phase separation in co-gelation (SPSiC) core–shell microgel that spontaneously forms from a homogeneous pre-gel solution of multiple polymers. The SPSiC microgel, composed of an alginate shell and an N-isopropylacrylamide (NIPAM) core, were synthesized by a single fabrication step wherein a mixed pre-gel solution of sodium alginate and NIPAM monomer was ejected by centrifugation with photo-polymerization and ion crosslinking instantaneously. Phase separation was modeled by varying the degree of polymerization and the size of the polymer chain. Moreover, an implantable, multi-functional drug delivery system combined with a transdermal glucose sensor was demonstrated with core–shell Janus SPSiC microgels. This work shows a macroscopic phase separation behavior, which occurs during the gelation process, and also provides a simple and unique methodology to create multifunctional bio-microprobes.

Glass surface micromachining with simultaneous nanomaterial deposition by picosecond laser for wettability control

Glass surface micromachining with simultaneous redeposition of nanomaterials in the vicinity of machined microscale trenches is achieved using a picosecond laser of visible wavelength in ambient air. After investigating the spatial distribution of redeposited nanomaterials by a unit discrete laser micromachining line, multi-line patterns machined with variable interline separations are characterized using optical and scanning electron microscopes. For large interline separations, laser machined debris was redeposited in the form of web-like nanofibrous aggregates with significant spatial variation in density. Reduced separations improved spatial uniformity but the increased material density induced noticeable conversion from web-like nanofibrous to fractal-like nano-cauliflower structures. In this way, picosecond laser machining processes enabled a single-step fabrication of multi-hierarchical micro/nanostructures on arbitrary glass surface areas with tunable nanomaterial structures. Based on the wetting behavior on patterned surfaces in ambient air by using the patterned surfaces as Wilhelmy plates in force-displacement measurements and in-situ optical microscope inspection, we find that contact angle hysteresis is suppressed for surfaces patterned with sufficiently small line separations due to the water infusion in the deposited nanomaterials. The studied laser processing method can be potentially employed for fast and effective fabrication of liquid infused surfaces with complex microscale patterns combined with controllable nanofeatures.

Nanoblocks embedded in L-shaped nanocavity of a plasmonic sensor for best sensor performance

In this work, we proposed a highly sensitive design of a plasmonic sensor which is formed by embedding a periodic array of nanoblocks in L-shaped cavity formed by the metal–insulator–metal waveguide. The nanoblocks are placed in the strong electric field confinement region to further enhance its strength by confining it to a small area. To validate the study, the spectral characteristics of the proposed sensor design is compared to the spectral characteristics of a standard design having the same geometric parameters excluding nanoblocks in the cavity. The study shows that the incorporation of 5 nanoblocks of length 25 nm in the cavity can provide best performance indicators in the form of sensitivity, figure of merit and Q-factor. The sensitivity, figure of merit and Q-factor of the proposed sensor design is 1065 nm/RIU, 251.17 and 343.4 which is significantly higher than the standard L-shape resonator design. The sensor design can be developed with a single fabrication step. Due to the ease of fabrication and the highly responsive nature of the design, it can be used in biomedical applications.

Highly Doped Si Single Crystal Nanowires via Metallic Flux Nanonucleation

Ever since the advent of scalable production of nanodevices, the search for optimal fabrication techniques of low dimensional materials has gained the attention of scientists and engineers all over the world. In particular, the fabrication of silicon nanowires is being increasingly investigated, due to their potential integration into novel technologies such as biological and optical sensors, solar cells, power generators, and transistors, among others. In this context, this work reports the single-step fabrication of Ga-doped Si bulk and nanowire single crystals. They were obtained through the Metallic Flux Nanonucleation (MFNN) technique, where a nanoporous alumina template was employed to define the nanowire morphology, while Ga was used as flux to both lower the Si melting point and dope the crystals. Our results show that Ga-doped silicon bulk crystals were successfully fabricated via MFNN. The carrier concentration was determined by probing the Hall effect and was found to be (2.5 ± 0.2) x 1019 cm−3. Silicon nanowires were simultaneously obtained, presenting an average wire diameter of 125 ± 26 nm and length up to several tens of microns. These results open the possibility to easily fabricate heavily doped intermetallic cylindrical nanowires, with versatility both on the nanowire composition and the doping element.

A facile one-pot synthesis of microgels and nanogels of laminarin for biomedical applications

HypothesisLaminarin (LAM) as a nontoxic, biodegradable, and biocompatible marine polysaccharide, has been reported for its ingenious bioactivities such as antioxidant, antitumor antiapoptotic anti-inflammatory, immunomodulatory and dietary fiber activities, and distinct physicochemical structure possess a remarkably promising potential in biomaterial science. Synthesis of LAM-based microgels and bulk hydrogels have been reported in two stages: modification of LAM polysaccharide with polymerizable functional groups and subsequent crosslinking reaction. Therefore, here an easier and more effortless methods to prepare poly(laminarin) (p(LAM)) particles were tackled. ExperimentalA direct and facile single step fabrication of micro/nanogels of p(LAM) for the first time by means of reverse micelle microemulsion system were illustrated. Preparation of p(LAM) particles were achieved by the well-known Oxa-Michael addition reaction mechanism using divinyl sulfone as the crosslinker. FindingsP(LAM) particles in 0.3–10 µm size range in spherical morphologies were prepared with 93 ± 7% yield and functionalized with chlorosulfonic acid (CSA) demonstrating their chemical modifiability for variety of agents e.g., targeting ligands. The bare and modified p(LAM) particles showed excellent blood compatibility with hemolytic indices of <1% and blood clotting indices higher than 90%. The reported p(LAM) particles hold great promise as natural alternative surrogates in biomedical applications including drug delivery.