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This paper explores methods to enhance the reproducibility of Josephson junctions, which are crucial elements in superconducting quantum technologies, when employing the Dolan technique in 30 kV e-beam processes. The study explores the influence of dose distribution along the bridge area on reproducibility, addressing challenges related to fabrication sensitivity. Experimental methods include e-beam lithography, with electron trajectory simulations shedding light on the behavior of backscattered electrons. Wedescribe the fabrication of various Josephson junction geometries and analyze the correlation between the success rates of different lithography patterns and the simulated distribution of backscattered electrons. Our findings demonstrate a success rate of up to 96.3% for the double-resist 1-step low-energy e-beam lithography process. As a means of implementation strategy, we provide a geometric example that takes advantage of simulated stability regions to administer a controlled, uniform dose across the junction area, introducing novel features to overcome the difficulties associated with fabricating bridge-like structures.
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Obtaining arrays of single nanoparticles with three-dimensional complex shapes is still an open challenge. Current nanolithography methods do not allow for the preparation of nanoparticles with complex features like nanostars. In this work, we investigate the optical printing of gold nanostars of different sizes as a function of laser wavelength and power. We found that tuning the laser to the main resonances of the nanostars in the near-infrared makes it possible to avoid nanoparticles reshaping due to plasmonic heating, enabling their deposition at the single particle level and in ordered arrays.
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The incorporation of sophisticated capabilities within microfluidic devices often requires the assembly of different layers in a correct arrangement. For example, when it is desired to include electrodes inside microfluidic channels or to create 3D microfluidic structures. However, the alignment between different substrates at the microscale requires expensive equipment not available for all research groups. In this work, we present an affordable, compact and portable aligner for assembling multilayered composite microfluidic chips. The instrument is composed of aluminum machined pieces combined with precision stages and includes a digital microscope with a LED illumination system for monitoring the alignment process. An interchangeable holder was created for substrate fixing, allowing the bonding of PDMS with other materials. Microscopic visualization is achieved through any device with internet access, avoiding the need of a computer attached to the aligner. To test the performance of the aligner, the center of an indium tin oxide microelectrode on a glass substrate was aligned with the center of a microchannel in a PDMS chip. The accuracy and precision of the instrument are suited for many microfluidic applications. The small and inexpensive design of the aligner makes it a cost-effective option for small groups working in microfluidics.
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Surface functionalization of polymers aims to introduce novel properties that favor bioactive responses. We have investigated the possibility of surface functionalization of polyethylene terephthalate (PET) sheets by the combination of laser ablation with hot embossing and the application of such techniques in the field of stem cell research. We investigated the response of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to topography in the low micrometer range. HiPSC-CMs are expected to offer new therapeutic tools for myocardial replacement or regeneration after an infarct or other causes of cardiac tissue loss. However, hiPSC-CMs are phenotypically immature compared to myocytes in the adult myocardium, hampering their clinical application. We aimed to develop and test a high-throughput technique for surface structuring that would improve hiPSC-CMs structural maturation. We used laser ablation with a ps-laser source in combination with nanoimprint lithography to fabricate large areas of homogeneous micron- to submicron line-like pattern with a spatial period of 3 µm on the PET surface. We evaluated cell morphology, alignment, sarcomeric myofibrils assembly, and calcium transients to evaluate phenotypic changes associated with culturing hiPSC-CMs on functionalized PET. Surface functionalization through hot embossing was able to generate, at low cost, low micrometer features on the PET surface that influenced the hiPSC-CMs phenotype, suggesting improved structural and functional maturation. This technique may be relevant for high-throughput technologies that require conditioning of hiPSC-CMs and may be useful for the production of these cells for drug screening and disease modeling applications with lower costs.
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Técnicas de Cultivo de Célula/métodos , Células Madre Pluripotentes Inducidas/citología , Miocitos Cardíacos/citología , Nanotecnología/métodos , Células Cultivadas , Ensayos Analíticos de Alto Rendimiento , Humanos , Tereftalatos Polietilenos/química , Propiedades de SuperficieRESUMEN
The study of patterned magnetic elements that can sustain more than one bit of the information is an important research line for developing new routes in magnetic storage and magnetic logic devices. Previous Monte Carlo studies of T-shaped magnetic nanostructures revealed the equilibrium and evolution of magnetic states that could be found as a result of the strong configurational anisotropy of these systems. In this work, for the first time, such behavior of T-shaped magnetic nanostructures is experimentally studied. In particular, T-shaped Co nanostructures have been produced by electron beam lithography using a single step lift-off process over Si substrates. The existence of four magnetic stable states has been proven by Magnetic Force Microscopy (MFM) and the analysis was complemented by Micromagnetic Simulations. The results confirmed that even for what can be considered large structures, with µm sizes, such four stable magnetic states can be achieved, and therefore two magnetic bits of information can be stored. We also addressed how to write and read those bits.
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Single-drop microextraction (SDME) was coupled with surface-enhanced Raman scattering (SERS) to provide sample extraction and pre-concentration for detection of analyte at low concentrations. A gold nanohole array substrate (AuNHAS), fabricated by interference lithography, was used as SERS substrate and para-mercaptobenzoic acid (p-MBA) was tested as a probe molecule, in the concentration range 10-8-10-4 mol L-1. With this approach, a limit of 10-7 mol L-1 was clearly detected. To improve the detection to lower p-MBA concentration, as 10-8 mol L-1, the SDME technique was applied. The p-MBA Raman signature was detected in two performed extractions and its new concentration was determined to be ~4.6 × 10-5 mol L-1. This work showed that coupling SDME with SERS allowed a rapid (5 min) and efficient pre-concentration (from 10-8 mol L-1 to 10-5 mol L-1), detection, and quantification of the analyte of interest, proving to be an interesting analytical tool for SERS applications.
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Microfluidics has become a very promising technology in recent years, due to its great potential to revolutionize life-science solutions. Generic microfabrication processes have been progressively made available to academic laboratories thanks to cost-effective soft-lithography techniques and enabled important progress in applications like lab-on-chip platforms using rapid- prototyping. However, micron-sized features are required in most designs, especially in biomimetic cell culture platforms, imposing elevated costs of production associated with lithography and limiting the use of such devices. In most cases, however, only a small portion of the structures require high-resolution and cost may be decreased. In this work, we present a replica-molding method separating the fabrication steps of low (macro) and high (micro) resolutions and then merging the two scales in a single chip. The method consists of fabricating the largest possible area in inexpensive macromolds using simple techniques such as plastics micromilling, laser microfabrication, or even by shrinking printed polystyrene sheets. The microfeatures were made on a separated mold or onto existing macromolds using photolithography or 2-photon lithography. By limiting the expensive area to the essential, the time and cost of fabrication can be reduced. Polydimethylsiloxane (PDMS) microfluidic chips were successfully fabricated from the constructed molds and tested to validate our micro-macro method.
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The controlled assembly of metal nanoparticles into ordered structures interacting with biological molecules is an emerging concept in surface science. Here, bare magnetite nanoparticles (Fe3O4-NPs) were employed as nanoadhesives to capture hollow metallic nanostructures (Au-Ag nanocages) from aqueous suspensions, and these coupled nanostructures were patterned onto various types of substrate via magnetolithography. Microwires of Au-Ag nanocages patterned onto an Au substrate behaved as optical antennas, providing a plasmonic enhancement exploited in surface-enhanced infrared absorption spectroscopy (SEIRAS) to investigate the proteins cytochrome c, bilirubin oxidase, alcohol dehydrogenase, bovine serum albumin, and glucose oxidase. Chemical maps containing more than 4000 spectra, acquired within only 2 min with a focal plane array detector, indicate that proteins were adsorbed along the microwires with their secondary structure preserved according to the spatial distribution of their amide groups. We believe there are significant practical aspects of the methodology proposed here to develop an alternative label-free assay for investigating biological molecules.
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Oro/química , Nanopartículas de Magnetita/química , Oxidorreductasas/química , Albúmina Sérica Bovina/química , Plata/química , Animales , Bovinos , Nanopartículas , Espectrofotometría InfrarrojaRESUMEN
In this work we demonstrate the use of a dielectric barrier discharge plasma for the treatment of SU-8. The resulting hydrophilic surface displays a 5° contact angle and (0.40 ± 0.012) nm roughness. Using this technique we also present a proof of concept of IgG and prostate specific antigen biodetection on a thin layer of SU-8 over gold via surface plasmon resonance detection.
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Micropatterning and manipulation of mammalian and bacterial cells are important in biomedical studies to perform in vitro assays and to evaluate biochemical processes accurately, establishing the basis for implementing biomedical microelectromechanical systems (bioMEMS), point-of-care (POC) devices, or organs-on-chips (OOC), which impact on neurological, oncological, dermatologic, or tissue engineering issues as part of personalized medicine. Cell patterning represents a crucial step in fundamental and applied biological studies in vitro, hence today there are a myriad of materials and techniques that allow one to immobilize and manipulate cells, imitating the 3D in vivo milieu. This review focuses on current physical cell patterning, plus chemical and a combination of them both that utilizes different materials and cutting-edge micro-nanofabrication methodologies.
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The fabrication of high-performance plasmonic nanomaterials for bio-sensing and trace chemical detection is a field of intense theoretical and experimental research. The use of metal-silicon nanopillar arrays as analytical sensors has been reported with reasonable results in recent years. The use of bio-inspired nanocomposite structures that follow the Fibonacci numerical architecture offers the opportunity to develop nanostructures with theoretically higher and more reproducible plasmonic fields over extended areas. The work presented here describes the nanofabrication process for a series of 40 µm × 40 µm bio-inspired arrays classified as asymmetric fractals (sunflower seeds and romanesco broccoli), bilaterally symmetric (acacia leaves and honeycombs), and radially symmetric (such as orchids and lily flowers) using electron beam lithography. In addition, analytical capabilities were evaluated using surface-enhanced Raman scattering (SERS). The substrate characterization and SERS performance of the developed substrates as the strategies to assess the design performance are presented and discussed.