Uniform Nanopatterns Research Articles

Objective-Free Ultrasensitive Biosensing on Large-Area Metamaterial Surfaces in the Near-IR.

Plasmonic metamaterials have opened new avenues in medical diagnostics. However, the transfer of the technology to the markets has been delayed due to multiple challenges. The need of bulky optics for signal reading from nanostructures patterned on submillimeter area limits the miniaturization of the devices. The use of objective-free optics can solve this problem, which necessitates large area patterning of the nanostructures. In this work, we utilize laser interference lithography (LIL) to pattern nanodisc-shaped metamaterial absorber nanoantennas over a large area (4 cm2) within minutes. The introduction of a sacrificial layer during the fabrication process enables an inverted hole profile and a well-controlled liftoff, which ensures perfectly defined uniform nanopatterning almost with no defects. Furthermore, we use a macroscopic reflection probe for optical characterization in the near-IR, including the detection of the binding kinematics of immunologically relevant proteins. We show that the photonic quality of the plasmonic nanoantennas commensurates with electron-beam-lithography-fabricated ones over the whole area. The refractive index sensitivity of the LIL-fabricated metasurface is determined as 685 nm per refractive index unit, which demonstrates ultrasensitive detection. Moreover, the fabricated surfaces can be used multiple times for biosensing without losing their optical quality. The combination of rapid and large area nanofabrication with a simple optical reading not only simplifies the detection process but also makes the biosensors more environmentally friendly and cost-effective. Therefore, the improvements provided in this work will empower researchers and industries for accurate and real-time analysis of biological systems.

Effect of Treated Time of Hydrothermal Etching Process on Oxide Layer Formation and Its Antibacterial Properties.

Inspired by natural materials, we developed an antibacterial surface on titanium (Ti) using hydrothermal etching techniques and examined the effect of treated time on oxide layer formation, its antibacterial properties, and surface defects. Hydrothermal etching was conducted on Grade 2 commercially pure Ti immersed in 5M NaOH at 250 °C during a range of time of 0–12 h. Nanopillars generated on the surface had ~100 nm thickness, which resulted in decreased attachment and rupturing of the attached bacteria. The results also showed that 6 h and 8 h of etching time provided a desirable uniform nanopillar structure with the most effective prevention of bacterial adherence on the surface. Multiscale SEM observations revealed that the longer the etching was conducted, the more cracks propagated, which led to an increase in dissociated fragments of the oxide layer. In the 12 h of etching, a higher density of bacterial adherence was observed than that of the untreated and the shorter time treated samples, indicating that etching took longer than 10 h worsened the antibacterial properties of the nano-patterned surface of Ti. This study demonstrated that the optimal time duration is 6–8 h for the oxide layer formation to maximize antibacterial activity and minimize cracking formation on the surface. For future studies, we suggest exploring many possible conditions to generate a more uniform nanopattern without structural defects to secure the integration between a newly deposited oxide layer and the substrate.

Mechanical reinforcement of UV-curable polymer nanocomposite for nanopatterned mold

This study proposed a method for manufacturing nanopatterned molds with high strength and durability using UV-curable polymer nanocomposites. Zirconia (ZrO2) nanoparticles (NPs) were blended with Ormostamp, a commercial UV-curable resin, using the solution blending method. The elastic modulus and hardness of the cured nanocomposite layer were investigated through a nanoindentation test for different volume ratios of NPs in the Ormostamp composite from 0 to 53.8%. The modulus and hardness of pure resin were 0.075 ± 0.002 GPa and 9.7 ± 0.164 MPa, respectively, and they increased to 11.9 GPa and 146.9 MPa at an NP concentration of 58.3%. Nanocomposite molds were fabricated by nanoimprinting with a PDMS stamp, which is replicated from the nanodimple array master. The fabricated nanocomposite mold can efficiently replicate other UV-curable resins. Hot embossing was then performed for a PMMA film using the fabricated molds. Unlike a pure UV-curable resin, which showed damage and fracture of the dimple structure after the first replication, the nanocomposites maintained the nanodimple shape even up to 30 replications. Uniform nanopatterns can be formed on even cylindrical surfaces by using a soft replica stamp. Polymer nanocomposites with a high NP concentration exhibited significantly improved mechanical reinforcement when compared to conventional pure polymers for mold making. Therefore, they are expected to be extremely useful for manufacturing nanopatterned molds using UV resin.

Diffraction-grating beam splitter, interferometric-lithography nanopatterning with a multilongitudinal-mode diode laser

Large-area, oblique-incidence interferometric nanopatterning using a low-cost multilongitudinal-mode diode laser as the source and a spin-on-glass based diffraction-phase-mask grating beam splitter is demonstrated. The phase mask is engineered to have only two equal intensity orders (0th and −1st), dramatically simplifying the optical arrangement and decreasing the propagation distance between the beam splitter and the sample. The low-cost, high-power (150 mW) TEM00 405-nm diode laser operates with a large number of longitudinal modes, resulting in an impractical mask-to-sample-gap proximity requirement. A dual-grating-mask, achromatic interferometric scheme is introduced to extend this gap dimension to easily accessible scales. Uniform nanopatterns with a periodicity of 600 nm were fabricated over a 1 cm diameter area using this multimode diode laser. This technique is scalable and has the potential for large-area nanopatterning applications.

Dual approach transformation of human finger and toe nail pruning into MgO/CaO nanoalloy

Interventions of biological entities mediated nanobiotechnological syntheses, in the strive to adapt inexpensive green approaches for constructing materials in the nanodimension for achieving targeted applications with improved performances, are being increasingly preferred. In context, this research article reports to bring into existence applaud able technique, concerning waste utilization for conversion into value added nanomaterial, to manage environmental issues as well as suffice biomedical demands and meet tough challenges from several domains. Pruning nail plates of the fingers and toes, has been a routine affair for the maintenance of personal care, in human civilization. Here we focus the bioengineering of MgO/CaO nanoalloy, by transforming remnant vestigial human finger and toe nail pruning, through dual approach protocols. Obtained yields through direct heat and following chemical treatment protocols were around 61.9% and 62.0%, respectively. Noticeable, quadrangular nanostructural arrangement in sequential array was observed for the MgO/CaO nanoalloy engineered through sol-gel chemical processing prior to thermal decomposition. Chemical treatment of the precursor enabled, formation of large stretches of uniform nanopattern and homogenous distribution to a great extent, from hydroxides of Mg and Ca instead of their salts. The scalable self-assembly with imparted ordered alignment shall inevitably manifest improved nanoalloy activity rather than the randomly distributed nanostuctures attained from direct thermal decomposition of their salts. The multifunctional green MgO/CaO nanoalloy, having tested thermal stability, consisting substantive Ca and Mg, incorporates the dual advantageous of nano MgO and nano CaO, logistically rendering superior benefits. Required characterizations were performed for the investigation of the significant nanostructures, comprising magnificent quadrangular nanobricks, nanorods and nanospheres, derived from the renewable bioresource.

"Fabrication Process Development of Uniform Nanopatterns on Lens Surface Via the Control of Focus Distance in Laser Interference Lithography"

Governments in all countries of the world today want organized and controlled societies that operate under a single set of rules and commands. Many governments around the world want and seek information that will allow them to control social groups and populations. Governments around the world set up ghost companies that were created to mislead the public and then collect information, data and then data from various sources or in collaboration with other third parties around the world. Somewhere here the game is changing, companies that are set up for information analysis often work for the benefit of third parties and governments. In a globalized world it is difficult to control the flow of data from both the extraction source and the final recipients.

External-energy-assisted nanomachining with low-stiffness atomic force microscopy probes

Thermal atomic force microscope (AFM) nanolithography enables many nanofabrication applications, but it requires special thermal probes. In this paper, we developed a vibration-assisted sample heating approach to implement the nanomachining of poly(methyl methacrylate) (PMMA) with a regular AFM probe with low stiffness (~0.16 N/m). The joule heating softens the PMMA, which lowers the normal force. The in-plane vibration with high frequency was applied to reduce the adhesion force between the AFM tip and the PMMA with elevated temperature, which enhances nanomachining performances. By using this approach, uniform nanopatterns with controllable dimensions were fabricated on PMMA films with small setpoint force.

Formation and Characterization of Hole Nanopattern on Photoresist Layer by Scanning Near-Field Optical Microscope.

Patterning of lines of holes on a layer of positive photoresist SX AR-P 3500/6 (Allresist GmbH, Strausberg, Germany) spin-coated on a quartz substrate is carried out by using scanning near-field optical lithography. A green 532 nm-wavelength laser, focused on a backside of a nanoprobe of 90 nm diameter, is used as a light source. As a result, after optimization of parameters like laser power, exposure time, or sleep time, it is confirmed that it is possible to obtain a uniform nanopattern structure in the photoresist layer. In addition, the lines of holes are characterized by a uniform depth (71–87 nm) and relatively high aspect ratio ranging from 0.22 to 0.26. Numerical modelling performed with a rigorous method shows that such a structure can be potentially used as a phase zone plate.

Use of beam-shaping optics for wafer-scaled nanopatterning in laser interference lithography

Laser interference lithography is a widely used technology for large-area patterning of surfaces on the micro- and nanoscale. It is mostly used for research purposes due to the limited area that can be uniformly patterned due to the Gaussian intensity profile of the laser. In the scope of this work, the lithography system was extended by a freeform refractive glass which provided a spatially uniform energy distribution for a homogenous structuring process. The energy variation of the introduced light was reduced to 2.6% for the exposed area (4 × 9 cm), which is one magnitude lower than the energy variation of a Gaussian beam. With the refractive beam shaper, it was possible to produce a uniform nanopattern with an absolute linewidth variation of 7 nm over an area of 4 × 9 cm2. The structurable area is limited by the mirror size of the Lloyd’s mirror device. The demonstrated LIL system was also able to generate variable light fields from Gaussian to flat-top as well as inverse Gaussian profiles. This paper demonstrates nanopatterning of negative resist with a square homogenous output profile of the beam shaper. The square shape of the beam profile gives the opportunity to efficiently structure substrates with a square shape. Apart from standard silicon-based photolithographic processes, this technique is also attractive for nanopatterning of organic light-emitting diodes on glass or graduated grid structures like polarizers. Consequently, the advantages of the LIL fabrication (high-throughput and low-cost fabrication) are extended by the opportunity to scale the single-exposure process to large areas with only small variations in the detail.

The effects of the bottom anti-reflective coating with different baked temperatures and thicknesses on nanoscale patterns

The bottom anti-reflective coating (BARC) material can enhance the resolution of the nanopatterns structures in laser interference lithography process. In this study, WIDE-B ARC material was investigated to confirm the reduction of the vertical standing wave which leads to defect of nanopatterns. And the critical dimension (CD) of 100nm L/S patterns with and without the application of BARC material was fabricated by laser interference lithography technology. The compared results showed that BARC can effectively reduce CD swing and obtain more uniform nanopatterns. Meanwhile, we also verified the influence of cured temperature and film thickness of BARC on the uniformity of nanopatterns.

Nanolithography. Large-scale nanoshaping of ultrasmooth 3D crystalline metallic structures.

We report a low-cost, high-throughput benchtop method that enables thin layers of metal to be shaped with nanoscale precision by generating ultrahigh-strain-rate deformations. Laser shock imprinting can create three-dimensional crystalline metallic structures as small as 10 nanometers with ultrasmooth surfaces at ambient conditions. This technique enables the successful fabrications of large-area, uniform nanopatterns with aspect ratios as high as 5 for plasmonic and sensing applications, as well as mechanically strengthened nanostructures and metal-graphene hybrid nanodevices.

Modifications in Morphology Resulting from Nanoimprinting Bulk Heterojunction Blends for Light Trapping Organic Solar Cell Designs

Nanoimprinting the photoactive layer of bulk heterojunction (BHJ) organic solar cells is a promising technique for enhancing device performance via improved light absorption. Here, we demonstrate that imprinting poly(3-hexylthiophene) (P3HT) and fullerene BHJ blends leads to adverse morphological changes within the photoactive nanopattern which have been previously overlooked. In particular, nanoimprinting induces a factor of 2 difference in polymer:fullerene composition between the nanopattern posts and interconnecting flash layer that inadvertently moves the composition outside the range for optimal performance. This occurs because of the strong tendency of regioregular P3HT to crystallize since imprinting blends based on amorphous regiorandom P3HT have uniform nanopattern composition. Based on these results, we outline promising design strategies, such as nanoimprinting amorphous polymers, to serve as guidelines for fabricating high-performance nanopatterned BHJ solar cells capable of maximized light absorption.

Highly sensitive localized surface plasmon resonance immunosensor for label-free detection of HIV-1

A highly sensitive label-free immunosensor for the detection of HIV-1 is newly developed based on localized surface plasmon resonance (LSPR) method. Uniform nanopattern of circular Au-dots (10-20nm) was fabricated on indium tin oxide (ITO) coated glass substrate by simple electrochemical deposition method. The surface of Au nanopattern was modified with HIV-1 neutralizing gp120 monoclonal antibody fragments. The modified substrate was employed to measure various concentrations of HIV-1 particles quantitatively based on the shift of longitudinal wavelength in the UV–Vis spectrum which results from the changes of local refractive index induced by specific antigen-antibody recognition events. The detection limit of the HIV-1 particles was estimated to be 200fg/mL, which is 10 fold higher than that of previously reported virus detection method based on LSPR. Since fabricated LSPR immunosensor has high sensitivity and selectivity, it is a promising approach for biological/medical sample analysis and various kinds of virus detection. From the Clinical EditorA localized surface plasmon resonance-based virus detection method is shown to have an order of magnitude improvement in detectable concentration of HIV-1 particles. Similar approaches may be used for screening other viral particles as well.

Fabrication and characterization of nanopatterned poly(ethylene oxide) thin films prepared from precursors formed in solution

Poly(ethylene oxide) (PEO) films with uniform nanopatterns were prepared by spin-coating dilute solutions containing crystallized PEO precursors onto silicon wafers. To form the precursors in solution, the PEO solutions were heated and incubated at 18°C with stirring for 6h. The blocky PEO stripes are uniformly distributed over the films and are arranged inside grain boundaries that form simple closed curves with distorted hexagonal shapes. In addition, an ordered silicon oxide stripe pattern was fabricated by using a nanopatterned PEO thin film as a template.

Tunable two-mirror interference lithography system for wafer-scale nanopatterning

We have designed and analyzed a novel (to the best of our knowledge) two-beam interference lithography system for large-area (wafer-level) nanopatterning with enhanced tunability of pattern periodicities. The tunable feature has been achieved by placing two rotational mirrors in the expanded beam paths at regulated angles for a desired period. Theoretical analyses show that the effective pattern coverage area greater than a 4 in. (10 cm) wafer scale is attainable with a 325 nm (30 cm coherence length) HeCd laser and 4 in. (10 cm) mirrors, while the pattern coverage area is restrained by the overruling effects between the optical coherence and mirror size. The experimental results also demonstrate uniform nanopatterns at varying periods (250-750 nm) on 4 in. (10 cm) substrates, validating the theoretical analyses. The tunable two-mirror interferometer will offer a convenient and robust way to prepare large-area nanostructures on a wafer scale with superior tunability in their pattern periodicities.

Improvement of the Non-Uniform Resist Patterns in the Thermal Nanoimprint Process Using Si Stamp with Nanoscale Rod Patterns

To acquire the uniform resist patterns in thermal nanoimprint lithography (TH-NIL), the major considerations include control of the resist, stamp and substrate resist under the imprint condition. Examples of these factors are management of the imprinting pressure, imprinting temperature and releasing temperature. Non-uniform patterns of thermal imprinted resist appear after TH-NIL according to the pattern size, substrate size and resist thickness. Particularly, the hole-shaped patterns with a diameter of 100 nm and a height of 100 nm on a 4 inch Si wafer after TH-NIL were deformed under tension to the maximum strain 70%. The experimental results showed that uniform nano-patterns can be acquired by minimizing the thermal mismatch while nanoimprinting through using a pair of Si stamp and Si substrate, thinning the resist thickness and separating the stamp at a relatively high temperature.

Fabrication of a Nanosize Pattern Embedded Plastic Chip via an Injection Molding Method for Application to an Optical Biosensor

Abstract We demonstrate a commercialized injection molding method for nano patterning of polymethyl methacrylate (PMMA) for the purpose of mass production of a label-free optical biosensor chip. Scanning electron microscope (SEM) images clearly show uniform nanopattern transfer on the plastic chip fabricated by an injection molding method. A uniformly deposited silicon nitride layer having a high refractive index by a plasma enhanced chemical vapor deposition (PECVD) technique is also observed. A unique characterization method is described wherein optical resonance reflection is used accurately and quickly to characterize the geometrical sensor structure. The authors anticipate that this robust method will provide an excellent means of producing an optical resonance reflection biosensor (ORRB).

Fabrication of Large Area Periodic Nanostructures Using Nanosphere Photolithography

Large area periodic nanostructures exhibit unique optical and electronic properties and have found many applications, such as photonic band-gap materials, high dense data storage, and photonic devices. We have developed a maskless photolithography method—Nanosphere Photolithography (NSP)—to produce a large area of uniform nanopatterns in the photoresist utilizing the silica micro-spheres to focus UV light. Here, we will extend the idea to fabricate metallic nanostructures using the NSP method. We produced large areas of periodic uniform nanohole array perforated in different metallic films, such as gold and aluminum. The diameters of these nanoholes are much smaller than the wavelength of UV light used and they are very uniformly distributed. The method introduced here inherently has both the advantages of photolithography and self-assembled methods. Besides, it also generates very uniform repetitive nanopatterns because the focused beam waist is almost unchanged with different sphere sizes.

Reprint of “Fabrication of nano-structures using inverse-μCP technique with a flat PDMS stamp”

Here, a new technology for uniform nano-patterning in a wide area is introduced. A μCP technique is applied in the opposite way of a traditional method. Using a flat PDMS stamp, sub-mm scale dot features of alkanethiol SAM are patterned onto rigid tips of micro Si structures, which deforms much less than those of PDMS structures. In order to minimize the diffusion of SAM ink in μCp process, the position of a stamp and a substrate is reversely changed, i.e., the Si substrate with micro structures is stamped onto the flat PDMS stamp which is placed on the bottom. Consequently, millions of nano dot features are uniformly patterned on the top of Si structures in a wide area (12 mm × 12 mm). As one application, millions of uniform nano-needles array is fabricated in a large area using a nano-scale metal mask fabricated by inverse-μCP. Besides, this inverse-μCP technique will show another possibility to the nano-fabrication for bio-MEMS technology.

Ge/Si Quantum Dot Formation From Non-Uniform Cluster Fluxes

The controlled growth of ultra-small Ge/Si quantum dot (QD) nuclei (≈1 nm) suitable for the synthesis of uniform nanopatterns with high surface coverage, is simulated using atom-only and size non-uniform cluster fluxes. It is found that seed nuclei of more uniform sizes are formed when clusters of non-uniform size are deposited. This counter-intuitive result is explained via adatom-nanocluster interactions on Si(100) surfaces. Our results are supported by experimental data on the geometric characteristics of QD patterns synthesized by nanocluster deposition. This is followed by a description of the role of plasmas as non-uniform cluster sources and the impact on surface dynamics. The technique challenges conventional growth modes and is promising for deterministic synthesis of nanodot arrays.