Nanofabrication Research Articles

Direct submicron patterning of titanium for bone implants

Recent research evidences the strong modulatory role of controlled submicron and nanoscale topographies on stem cells fate. To harness these physical surface cues for clinical applications, fabrication of nano- and submicron patterns on clinically relevant biomaterials is greatly needed. In this study, an electron beam lithography method for direct patterning (i.e., no use of masters/imprinting steps) of titanium in the submicron range was developed. The process required the use of an etch mask consisting of a double layer of SiO2 and Al, and the positive AR P-6200.04 electron beam resist. An optimum electron beam dose of 288 μC/cm2 was established for writing the desired patterns. The transfer of the patterns into the titanium substrates was achieved by three different steps: inductively coupled plasma etching of the mask in BCl3/Cl2 followed by reactive ion etching of titanium in SF6/CHF3/O2 and a final wet etch of mask residue. Highly ordered arrays of titanium pits with submicron diameters were produced with high reproducibility. This method provides great versatility in pattern design, direct transfer into titanium and increased control of titanium pattern features at submicron to nanoscale enabling clinically relevant and systematic studies on pattern-induced cellular responses.

Microfluidics in nanoparticle drug delivery; From synthesis to pre-clinical screening

Microfluidic technologies employ nano and microscale fabrication techniques to develop highly controllable and reproducible fluidic microenvironments. Utilizing microfluidics, lead compounds can be produced with the controlled physicochemical properties, characterized in a high-throughput fashion, and evaluated in in vitro biomimetic models of human organs; organ-on-a-chip. As a step forward from conventional in vitro culture methods, microfluidics shows promise in effective preclinical testing of nanoparticle-based drug delivery. This review presents a curated selection of state-of-the-art microfluidic platforms focusing on the fabrication, characterization, and assessment of nanoparticles for drug delivery applications. We also discuss the current challenges and future prospects of nanoparticle drug delivery development using microfluidics.

Improvement in current density of nano- and micro-structured Si solar cells by cost-effective elastomeric stamp process

Effective incident light should be controlled for improving the current density of solar cells by employing nano- and micro-structures on silicon surface. The elastomeric stamp process, which is more cost effective and simpler than conventional photolithography, was proposed for the fabrication of nano- and micro-structures. Polydimethylsiloxane (PDMS) was poured on a mother pattern with a diameter of 6 μm and a spacing of 2 μm; then, curing was performed to create a PDMS mold. The regular micropattern was stamped on a low-viscosity resin-coated silicon surface, followed by the simple reactive ion etching process. Nano-structures were formed using the Ag-based electroless etching process. As etching time was increased to 6 min, reflectance decreased to 4.53% and current density improved from 22.35 to 34.72 mA/cm2.

Voltammetric sensing based on the use of advanced carbonaceous nanomaterials: a review.

This review (with 210 references) summarizes recent developments in the design of voltammetric chemical sensors and biosensors based on the use of carbon nanomaterials (CNMs). It is divided into subsections starting with an introduction into the field and a description of its current state. This is followed by a large section on various types of voltammetric sensors and biosensors using CNMs with subsections on sensors based on the use of carbon nanotubes, graphene, graphene oxides, graphene nanoribbons, fullerenes, ionic liquid composites with CNMs, carbon nanohorns, diamond nanoparticles, carbon dots, carbon nanofibers and mesoporous carbon. The third section gives conclusion and an outlook. Tables are presented on the application of such sensors to voltammetric detection of neurotransmitters, metabolites, dietary minerals, proteins, heavy metals, gaseous molecules, pharmaceuticals, environmental pollutants, food, beverages, cosmetics, commercial goods and drugs of abuse. The authors also describe advanced approaches for the fabrication of robust functional carbon nano(bio)sensors for voltammetric quantification of multiple targets. Graphical Abstract Featuring execellent electrical, catalytic and surface properies, CNMs have gained enormous attention for designing voltammetric sensors and biosensors. Functionalized CNM-modified electrode interfaces have demonstrated their prominent role in biological, environmental, pharmaceutical, chemical, food and industrial analysis.

The mechanism of catalase loading into porous vaterite CaCO3 crystals by co-synthesis.

Porous vaterite CaCO3 crystals are nowadays extensively used as high-capacity bio-friendly sacrificial templates for the fabrication of such protein-containing nano- and micro-particles as capsules and beads. The first step in the protein encapsulation is performed through loading of the protein molecules into the crystals. Co-synthesis is one of the most useful and simple methods proven to effectively load crystals with proteins; however, the loading mechanism is still unknown. To understand the mechanism, in this study, we focus on the loading of a model protein catalase into the crystals by means of adsorption into pre-formed crystals (ADS) and co-synthesis (COS). Analysis of the physico-chemical characteristics of the protein in solution and during the loading and simulation of the protein packing into the crystals are performed. COS provides more effective loading than ADS giving protein contents in the crystals of 20.3 and 3.5 w/w%, respectively. Extremely high loading for COS providing a local protein concentration of about 550 mg mL-1 is explained by intermolecular protein interactions, i.e. formation of protein aggregates induced by CaCl2 during the co-synthesis. This is supported by a lower equilibrium constant obtained for COS (5 × 105 M-1) than for ADS (23 × 105 M-1), indicating a higher affinity of single protein molecules rather than aggregates to the crystal surface. Fitting the adsorption isotherms by classical adsorption models has shown that the Langmuir and BET models describe the adsorption phenomenon better than the Freundlich model, proving the aggregation in solution followed by adsorption of the aggregates into the crystals. We believe that this study will be useful for protein encapsulation through CaCO3 crystals using the COS method.

CHARACTERIZATION OF THE ELECTROPHYSICAL PROPERTIES OF SILICON-SILICON DIOXIDE INTERFACE USING PROBE ELECTROMETRY METHODS

Introduction of submicron design standards into microelectronic industry and a decrease of the gate dielectric thickness raise the importance of the analysis of microinhomogeneities in the silicon-silicon dioxide system. However, there is very little to no information on practical implementation of probe electrometry methods, and particularly scanning Kelvin probe method, in the interoperational control of real semiconductor manufacturing process. The purpose of the study was the development of methods for nondestructive testing of semiconductor wafers based on the determination of electrophysical properties of the silicon-silicon dioxide interface and their spatial distribution over wafer’s surface using non-contact probe electrometry methods.Traditional C-V curve analysis and scanning Kelvin probe method were used to characterize silicon- silicon dioxide interface. The samples under testing were silicon wafers of KEF 4.5 and KDB 12 type (orientation <100>, diameter 100 mm).Probe electrometry results revealed uniform spatial distribution of wafer’s surface potential after its preliminary rapid thermal treatment. Silicon-silicon dioxide electric potential values were also higher after treatment than before it. This potential growth correlates with the drop in interface charge density. At the same time local changes in surface potential indicate changes in surface layer structure.Probe electrometry results qualitatively reflect changes of interface charge density in silicon-silicon dioxide structure during its technological treatment. Inhomogeneities of surface potential distribution reflect inhomogeneity of damaged layer thickness and can be used as a means for localization of interface treatment defects.

Print‐Light‐Synthesis of Platinum Nanostructured Indium‐Tin‐Oxide Electrodes for Energy Research

AbstractPrint‐light‐synthesis is a new concept for the large‐scale in situ fabrication of nanoparticles and structures on large substrates. Here, Pt nanoparticles are synthesized on indium tin oxide (ITO) coated glass slides by using combined inkjet printing and photonic curing operated under ambient conditions and with low material usage. A formulated chloroplatinic acid based ink provides stable and reproducible jetting, optimized ink–substrate interaction and fast ink drying to create well‐defined thin precursor films acting as nanoreactors. The precursor loading is precisely controlled by the printing parameters. Then, a short light pulse from a Xe flash lamp fully converts the printed Pt precursor containing film into pure Pt nanoparticles. The optimum precursor coverage is ≈1 µg mm−2 Pt consuming as less as ≈50 nL mm−2 of ink. Neither reducing nor capping agents are used resulting in pure Pt nanoparticles (30 nm average size) and micrometer‐size aggregates. The nanostructures are well‐adhered to the ITO substrate and show a stable electrochemical performance for the oxygen reduction reaction. The fast and cost‐effective process optimization in terms of ink formulation, substrate pre‐treatment, inkjet printing resolution, and post‐processing for the rapid fabrication of Pt nano‐ and microparticle‐coated ITO electrodes is presented and discussed.

An Insight on Silk Protein Sericin: From Processing to Biomedical Application.

Silks are naturally occurring polymers that have been used clinically as sutures for hundreds of years. It's so for obtained from insects or worms, silk consists of a filament core protein, termed fibroin, and a glue-like coating made up of sericin proteins. An important component of silk has an extended history of being discarded as a waste in the course of silk processing. The cost of sericin for tissue engineering is underestimated and its capability in using as regenerative remedy has simply began to be explored. Its variable amino acid composition and various functional groups confer upon it attractive bioactive proteins, which are particularly interesting for biomedical programs. Because of its antioxidant properties, moisturizing ability, and mitogenic effect on mammalian cells, sericin is beneficial in cell regeneration and tissue engineering. Research shows that keratinocytes and fibroblasts have brought about the improvement of sericin-primarily based biomaterials for skin tissue repair, in particular as wound dressings. Moreover, sericin may be used for bone tissue engineering due to its ability to set off nucleation of bone-like hydroxyapatite. Stable silk sericin biomaterials, as films, sponges, and hydrogels, are obtained by means of cross-linking, ethanol precipitation, or mixing with different polymers. Now a day, sericin may also be used for delivery of drugs due to its chemical reactivity and pH-responsiveness which facilitate the fabrication of nano and microparticles, hydrogels, and conjugated molecules, enhancing the bioactivity of drugs. In this review, we outlined the current headways from extraction of sericin till its physical properties and biomedical applications.

Micro- and nanofluidic systems in devices for biological, medical and environmental research

The use of micro- and nanofluidic systems in modern analytical instruments allow you to implement a number of unique opportunities and achieve ultra-high measurement sensitivity. The possibility of manipulation of the individual biological objects (cells, bacteria, viruses, proteins, nucleic acids) in a liquid medium caused the development of devices on microchip platform for methods: chromatographic and electrophoretic analyzes; polymerase chain reaction; sequencing of nucleic acids; immunoassay; cytometric studies. Development of micro and nano fabrication technologies, materials science, surface chemistry, analytical chemistry, cell engineering have led to the creation of a unique systems such as “lab-on-a-chip”, “human-on-a-chip” and other. This article discusses common in microfluidics materials and methods of making functional structures. Examples of integration of nanoscale structures in microfluidic devices for the implementation of new features and improve the technical characteristics of devices and systems are shown.

Large area multi-channel plasmonic absorber based on the touching triangular dimers fabricated by angle controlled colloidal nanolithography

Here we introduce large area plasmonic touching triangular dimers by angle controlled colloidal nanolithography to use them asan efficient multi channel absorber and also high figure of merit sensors. For this purpose, we coated gold thin films onto nanometric and also micrometric polystyrene hexagonal closed packed masks in different deposition angles and also diverse substrate polar angles. Our prepared samples, after remove masks, show large area touching triangular pattern with different inter particle distances in greater polar angles. To get more sense about optical response of the samples such as transmittance and also electric field distribution, we use finite difference time domain method in simulation part. The transmittance plot shows one narrow or multi-channel adjustable deep depend on inter-particle distances which can be controlled by azimuthally angle in nano lithography process. Also, due to the isoelliptical points in the transmittance spectra; we can see the bright and dark plasmon modes coupling and thus the Fano like resonance takes place in the optical spectral region which is very useful for refractive index measurement.

Design of Low-Power High-Performance FinFET Standard Cells

With the leakage power becoming a most important concern in deep sub-micron designs, the advent of FinFET offers promising options due to its superior electrical properties and design flexibility. To support the VLSI digital system design flow based on the standard cells in FinFET, the building method of optimized FinFET standard cells is proposed. This method is derived on the basis of jointly optimizing the back-gate voltages and the width to length ratio of the transistors in the stacked structure in each standard cell under the premise of maintaining the performance. By employing this design method, optimized standard cells are generated and form a low-power high-performance standard cell library. Simulation results of the standard cells designed with our proposed method demonstrate that the leakage power can be reduced by a factor of 47.99 at most while the worst-case delay can achieve a maximum reduction of 10.17%. Monte Carlo simulation results illustrate that the optimized cells can gain more dependability to process variations and environmental changes. The 16-bit ripple carry adder implemented with this optimized FinFET library can obtain a maximum leakage power reduction of 59.6% and a worst-case delay reduction of 21.8%.

Novel fabrication of nano functionalized amorphous tungsten oxide coatings with colorful superamphiphobic surface study

Fabrication of surfaces with capability of repelling both water and oil is badly needed. Meanwhile, the widespread use of nanomaterials has also attracted great interest in this field. In this paper, we provided novel methods to synthesize nano amorphous tungsten oxide coatings on Al-Mg metals. After modification with FAS-17, the surface could obtain excellent superamphiphobic abilities with lower sliding angles and higher contact angles to water and oil. In addition, outstanding anti-oil pollutant and low adhesion were obtained. Furthermore, the as-prepared superamphiphobic surfaces could survive 200cm abrasion distance under 19.6kPa pressure on 1000grid SiC sandpaper. It should be noted that this coatings could obtain different colors in different temperature. Meanwhile, we found that the droplets with lower surface energy and low viscosity are easier to bounce than the droplets with high surface energy and high viscosity. So the simple procedure and excellent superamphiphobicity about fabricating colorful tungsten oxide coatings have great potential in protecting Al-Mg metal and have potential applied in signals which need to prevent wetting or pollution by water and oils. On one level, this method about synthesizing nano amorphous tungsten oxide also has more promising using in other fields.

Plasma generation in liquid as a new efficient synthesis approach of titania–zinc ferrite nano(photo)catalyst

In the past years, an important problem that requires solutions at the global scale is the environmental pollution. This work describes a possible approach toward finding such solutions based on nanophotocatalysts with improved activity. Thus, the present study reports a new and efficient synthesis procedure for titania–zinc ferrite nanocomposite with enhanced photodegradation activity. The method is based on the liquid phase plasma technique and follows a bottom-up scheme. The resulted materials have been compared with those synthesized by the ultrasound-assisted method. Using the plasma-assisted procedures in the fabrication of an efficient nano(photo)catalyst decreases considerably the reaction time. The liquid phase plasma generates nanoparticles with enhanced structural, textural, and morphological properties as demonstrated by X-ray diffraction, nitrogen sorption, transmission electron microscopy, and small-angle X-ray scattering.

Calcium Silicate/Chitosan-Coated Electrospun Poly (Lactic Acid) Fibers for Bone Tissue Engineering.

Electrospinning technology allows fabrication of nano- or microfibrous fibers with inorganic and organic matrix and it is widely applied in bone tissue engineering as it allows precise control over the shapes and structures of the fibers. Natural bone has an ordered composition of organic fibers with dispersion of inorganic apatite among them. In this study, poly (lactic acid) (PLA) mats were fabricated with electrospinning and coated with chitosan (CH)/calcium silicate (CS) mixer. The microstructure, chemical component, and contact angle of CS/CH-PLA composites were analyzed by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. In vitro, various CS/CH-coated PLA mats increased the formation of hydroxyapatite on the specimens’ surface when soaked in cell cultured medium. During culture, several biological characteristics of the human mesenchymal stem cells (hMSCs) cultured on CS/CH-PLA groups were promoted as compared to those on pure PLA mat. Increased secretion levels of Collagen I and fibronectin were observed in calcium silicate-powder content. Furthermore, with comparison to PLA mats without CS/CH, CS10 and CS15 mats markedly enhanced the proliferation of hMSCs and their osteogenesis properties, which was characterized by osteogenic-related gene expression. These results clearly demonstrated that the biodegradable and electroactive CS/CH-PLA composite mats are an ideal and suitable candidate for bone tissue engineering.

Electrochemical effect of Copper Gleam additives during copper electrodeposition

Electrochemical nano and micro fabrication by flow and chemistry is a maskless micro-patterning technology that uses an acid-free and low ion concentration electrolyte. However, the effects of additives on the electrochemical behaviour of this type of electrolyte are still unknown; hence, their role during micro- and nano-fabrication is unpredictable. This study reports the effect of a suppressor (Copper Gleam B), an accelerator (Copper Gleam A) and a promoter (Cl−) on the electrochemical behaviour of copper reduction. The three additives, when employed separately, were found to increase cathode polarisation. The combination of Copper Gleam B and Cl− showed strong inhibition, particularly in the diffusion-limited region. The addition of Copper Gleam A to the Copper Gleam B–Cl− mix increased the limiting current and suggested plating acceleration. These effects are interpreted in terms of the adsorption–desorption behaviour of the additives on the cathode surface.

Development of Optimized Nanogap Plasmonic Substrate for ImprovedSERS Enhancement

SERS enhancement factor (EF) of planar substrates depends on the size and shape of the fine nanostructure forming a defect free, well-arranged matrix. Nano-lithographic process is considered to be the most advanced methods employed for the fabrication SERS substrates. Nanostructured plasmonic substrates with nanogap (NGs) pattern are often results in stable, efficient and reproducible SERS enhancement. For such substrates, NG and their diagonal length (DL) need to be optimized. Theoretically smaller NGs (~30-40 nm or smaller) results in higher SERS enhancement. However, fabrication of NG substrates below such limit is a challenge even for the most advanced lithography process, In this context, herein, we report the optimization of fabrication process, where higher SERS enhancement can be realized from larger NGs substrates by optimizing their DL of nanostructures between the NGs. Based on simulation we could demonstrate that, by optimizing the DL, SERS enhancement from larger NG substrate such as 60 and 80 nm could be comparable to that of smaller (40 nm) NG substrates. We envision that this concept will open up new regime in the nanofabrication of practically feasible NG based plasmonic substrates with higher SERS enhancement. Initial results of our experiments are in close agreement with our simulated study.

Detection of Pathogenic Bacteria: A Genosensor Approach

Nowadays detection of pathogenic bacteria is one of the major concerns in food beverage drinking water and pharmaceutical industries The traditional methods used for identification of bacteria involve detection of characteristic metabolites or cellular reproductive cycles which is time consuming less sensitive and misleading From last few decades there has been a great advance in the strategies for detection of pathogenic bacteria by using micro and nano fabrication technologies These technologies largely improved the sensitivity specificity limit of detection and simultaneously reduced the complexity of handing time and cost of detection The paper will be focused on newly developed nano and micro scaled sensors microfluidics lab on a chip and array based technologies for the detection of different pathogenic bacteria

Assessing Nanofabrication Performance Based on the Estimated Taguchi Capability Index with Subsamples

The Taguchi capability index C_(pm) has been proposed to the manufacturing industry for measuring manufacturing capability. Investigations of the estimated Taguchi capability index based on subsamples have been proposed and arrested substantial research attention. In this paper, investigation based on subsamples is considered for normally distributed processes from the traditional distribution frequency approach. A reliable inferential procedure based on subsamples of the estimated Taguchi capability index is proposed. Computational programs using Matlab software are proposed to calculate p-values and critical values required to ensure the process reaching a certain desirable level of the time. A practical example is provided to demonstrate how the proposed procedure may be applied for judging whether the process runs under the desirable quality requirement.

Analysis on Mechanical Property for Varied Geometry and Structure Parameters of Silicon Based Filtration Membrane for Artificial Kidney

Silicon and Silicon Nitride are vigorously utilized and explored in micro and nano fabrication technology as they have excellent mechanical and electrical characteristics suitable for NEMS device application. In this study, both of them are analyzed using COMSOL Multiphysics software to evaluate the strength capability of the material when used as filtration membrane in artificial kidney. The artificial filtration membrane is a crucial part in an artificial kidney system as it functions to filter out all wastes from blood stream. This paper investigates the effect of membrane thickness experiencing applied pressure of 1332.3 Pa and 7332.7 Pa on membrane deflection and von Mises stress at the center of the filtration membrane. Those mechanical characteristics at different pore geometry and structure are evaluated against applied pressure on the filtration membrane surface. The results show that the pore geometry and shape for a membrane with thickness of higher than 200 nm will not have significant influences on the deflection and stress characteristics. Therefore, thicker membrane will result to a more stable filtration process that would be able to withstand simulated blood stream pressure in an artificial kidney.

Designing of Lay-Out Optimization of Vlsi Devices and Interconnects In Deep Submicron Designs

Designing of Lay-Out Optimization of Vlsi Devices and Interconnects In Deep Submicron Designs