Nanomolding Process Research Articles

Molecularly imprinted fluoroprobes doped with Ag nanoparticles for highly selective detection of oxytetracycline in real samples

A molecularly imprinted polymer (MIP), which is synthesized by a nanomolding process around a template, has emerged as a promising analytical tool for environmental quality monitoring and food safety test. In this work, a fluoroprobe with Ag-doped MIP nanolayer (16 nm thickness) is successfully prepared for the highly selective detection of oxytetracycline (OTC) in real samples (i.e. Yangtze River water, swine urine). In the MIP nanolayer, two functional monomers (i.e. 4-(2-acrylamidoethylcarbamoyl)-3-fluorophenylboronic acid, methacrylic acid) synergistically constitute the specific recognition sites. Meanwhile, the doped Ag enhances the detection sensitivity (with a detection limit of 5.38 nM) and accelerates the detection rate (within 2.5 min) even in real samples. Therefore, the present study paves the way for the preparation of MIP-based fluoroprobes, showing great prospects in environmental quality and food safety tests.

General Nanomolding of Ordered Phases.

Large-scale, controlled fabrication of ordered phases is challenging at the nanoscale, yet highly demanded as their well-ordered structure and chemistry is the key for advanced functionality. Here, we demonstrate a general nanomolding process of ordered phases based on atomic diffusion. Resulting nanowires are single crystals and maintain their composition and structure throughout their length, which we explain by a self-ordering process originating from their narrow Gibbs free energy. The versatility, control, and precision of this thermomechanical nanomolding method of ordered phases provides new insights into single crystal growth and suggest itself as a technology to enable wide spread usage for nanoscale and quantum devices.

Controlled fabrication of gold nanotip arrays by nanomolding-necking technology

The fabrication of nanotips has been driven by the increasing industrial demands in developing high-performance multifunctional nanodevices. In this work, we proposed a controlled, rapid as well as low cost nanomolding-necking technology to fabricate gold nanotips arrays. The geometries of gold nanotips having cone angle range of ∼28–77° and curvature radii of <5 nm can be prepared by tailoring the diameters of raw nanorods in nanomolding process or modulating the necking temperature. Molecular dynamics simulation reveals that the formation of the nanotip geometry is determined by the interplay between dislocation-based and diffusion-based deformation mechanisms, intrinsically arising from the nonlinear dependence of atom diffusion on temperature and sample size. The good controllability, mass production and low cost of the developed nanomolding-necking technology make it highly promising in developing nanodevices for a wide range of applications, such as probing, sensing, antireflection coating and nanoindentation.

Nanorod Array Structure Through a Nanomolding Process for Semiconductor Lighting and Display Applications

Three-dimensional structure and growth can be more appropriately realized through a nanomanufacturing process that uses a mask patterning and etching process. Unlike conventional single-wavelength semiconductor lighting sources, the uniformity and reproducibility of the nanomolding process in this study enable multiple wavelengths to be used in lighting and display applications. This study shows the various wavelength characteristics through a newly developed nanomold and its nanorod array and also proves the feasibility of a white light without phosphors for emitting multiple wavelengths from a single chip. In this study, we proposed the possibility of wavelength control by fabricating a light-emitting diode with a three-dimensional nanostructure, using a nanomold with semiconductor processing.

Fabrication of Randomly Stooped Polymer Nanohairs Using Scattered Electron Flood under Ambient Condition

Despite attractive applications of randomly oriented nanostructures with high aspect ratio, their fabrication suffers from both complicated processes and lack of materials. In this letter, we present a simple but effective method for the fabrication of randomly stooped polymeric nanohairs havinghigh aspect ratio under ambient condition by using scattered electron flood. High aspect ratio vertical nanohairs prepared by nano-molding process exhibited randomly stooped geometry after the electron irradiation. Fourier transform infrared spectroscopy and Monte Carlo simulation revealed that radiolysis of polymeric nanohairs by scattered electrons in ambient air allowed directionally random distribution of shrinkage of the nanohairs, resulting in randomly stooped nanohair structures.

Shaping Resonant Light Confinement and Optoelectronic Spectra Using Strain in Hierarchical Multiscale Structures

AbstractHierarchically structured optical materials have been a topic of intriguing research interest due to the possibility of tailoring material properties beyond the limits of bulk continuum material design. Here, an optical confinement phenomenon in a hierarchically structured waveguide platform consisting of alternating clusters of nanostructured and planar microscale domains is demonstrated. An unconventional self‐assembly‐based strain‐assisted nanomolding process is developed to fabricate these hierarchically structured multiperiodic waveguides. Further, these hierarchically patterned waveguides are used as substrates for solution‐processed photodetectors. The optical confinement occurring due to the nanoscale scattering and the wavelength‐dependent interaction between the planar and structured microdomains leads to an improved uniformity in the optoelectronic spectral response of these photodetectors. Furthermore, by tuning the multiperiodicity within the nanostructured domain structure, using a mechanical strain of 20%, an improvement of around 10% in the uniformity of the optoelectronic spectral response of the photodetectors is demonstrated. Simulations further show that these processes arise only in the presence of a hierarchical structure, due to multiscale interaction, through wavelength‐selective coupling of scattered light from nanostructured domains to the planar microdomains. In summary, hierarchical structures can address optoelectronic problems that cannot be addressed by simpler structures.

Nanomolding of Crystalline Metals: The Smaller the Easier.

We report on a thermomechanical nanomolding method for crystalline metals. Quantified by the aspect ratio, this process becomes easier with decreasing mold diameter. As the responsible underlying diffusion mechanism is present in all metals and alloys, the discovered nanomolding process provides a toolbox to shape essentially any metal and alloy into a nanofeature. Technologically, this highly versatile and practical thermomechanical nanomolding technique offers a method to fabricate high-surface-area metallic nanostructures which are impactful in diverse fields of applications including catalysts, sensors, photovoltaics, microelectronics, and plasmonics.

3D nanomolding and fluid mixing in micromixers with micro-patterned microchannel walls

Microfluidic devices where the microchannel walls were decorated with micro and nanostructures were fabricated using 3D nanomolding. Using 3D molded microfluidic devices with microchannel walls decorated with microscale gratings, the fluid mixing behavior was investigated through experiments and numerical simulation. The use of microscale gratings in the micromixer was predicated by the fact that large obstacles in a microchannel enhances the mixing performance. Slanted ratchet gratings on the channel walls resulted in a helical flow along the microchannel, thus increasing the interfacial area between fluids and cutting down the diffusion length. Increasing the number of walls decorated with continuous ratchet gratings intensified the strength of the helical flow, enhancing mixing further. When ratchet gratings on the surface of the top cover plate were aligned in a direction to break the continuity of gratings from the other three walls, a stack of two helical flows was formed one above each other. This work concludes that the 3D nanomolding process can be a cost-effective tool for scaling-up the fabrication of microfluidic mixers with improved mixing efficiencies.Graphical abstractIn this paper we show that a micromixer with patterned walls can be fabricated using 3D nanomolding and solvent-assisted bonding to manipulate the flow patterns to improve mixing.

Revealing High Fidelity of Nanomolding Process by Extracting the Information from AFM Image with Systematic Artifacts

A contact mode atomic force microscopic (c-AFM) study has been carried out to realize the high fidelity of a nanomolding process where nanostructures fabricated on a silicon master are replicated onto an aluminum surface. The AFM images of the nanostructures show systematic artifacts due to the finite size of the AFM tip and thus set a limitation to the estimation in the fidelity of the nanomolding process. The quantitative analysis presented in this letter enables to extract the parameters necessary to reveal the high fidelity of the nanomolding process while the real width and the depth of the nanostructures are still unknown. This work provides a direction to the researches in the field of atomic force microscopy of nanostructures to analyze the data accurately in presence of systematic artifacts.

Replication of rose-petal surface structure using UV-nanoimprint lithography

Rose-petal surface consists of a hierarchical structure of microscale papillae and nanofolds. With this micro-nanostructure and surface energy, rose petals exhibit a special property: drops on the petal surface are spherical and do not slide when a petal is held upside down. We replicated the rose-petal surface structure by employing a UV nanomolding process using polyurethane acrylate (PUA) for the first replica and perfluoropolyether (PFPE) for the second replica. PFPE micro-nanostructures, which were identical to the rose-petal hierarchical structure, were formed on a glass substrate. The water contact angle of 144° and contact-angle hysteresis of 83° confirmed that the surface of the glass substrate exhibited a high adhesive force and superhydrophobicity.

Biomimetic soft lithography on curved nanostructured surfaces

In this paper a nano-molding process using a nature-created master is demonstrated. The eye of night moth Agotis exclamationis having 100 nm-scale structures on a curved surface is used as biomimetic master mold from which nanostructures are replicated onto a flat substrate. Suitable conditions of this simple and cost-efficient process allows for minimal texture damage. The fabrication consists of two steps: first, a negative PDMS mold of the curved eye surface is made, and second, the flexible mold is replicated into a hybrid UV sensitive polymer, on a flat substrate. An accurate copy of the master surface with dense arrays of 200 nm high and 100–120 nm wide posts are generated, thus preserving the integrity of the nanostructures. The known anti-reflecting optical properties of the moth eye were reproduced with a reflectivity reduced by a factor of 2.

Polymer structure and properties in micro- and nanomolding process

Injection molding of thin-wall parts with micro/nano-scale patterns using various polymers was performed to clarify the processability and surface replication of molded parts. Effects of process conditions on processability, higher-order structure and surface properties of molded parts were evaluated. The optical anisotropy in the vicinity of the gate became higher than at any other positions. The height replication ratio of surface patterns increased with increasing injection speed, holding pressure, injection temperature and mold temperature. In the case of nanomolding, negative birefringence toward the flow direction appeared higher than at the skin–shear region from the observation of skin–shear and core structure inside molded parts. Thus, the molecular orientation axis was oriented along the thickness direction because of deformation during the demolding process. Thermal stability of nano-surface patterns was influenced by the size of surface features and internal higher-order structure.

Nanoscale patterning of magnetic islands by imprint lithography using a flexible mold

A nanomolding process for producing 55-nm-diameter magnetic islands over 3-cm-wide areas is described. A master pattern of SiO2 pillars is used to form a polymeric mold, which is in turn used to mold a photopolymer resist film. This latter film is used as a resist for etching SiO2, yielding a pattern of pillars. Finally, an 11-nm-CoPt multilayer is deposited. Magnetic force microscopy reveals that the film on top of each pillar is a magnetically isolated single domain that switches independently.