High-precision Patterns Research Articles

Bubble wall confinement-driven molecular assembly toward sub-12 nm and beyond precision patterning.

Patterning is attractive for nanofabrication, electron devices, and bioengineering. However, achieving the molecular-scale patterns to meet the demands of these fields is challenging. Here, we propose a bubble-template molecular printing concept by introducing the ultrathin liquid film of bubble walls to confine the self-assembly of molecules and achieve ultrahigh-precision assembly up to 12nanometers corresponding to the critical point toward the Newton black film limit. The disjoining pressure describing the intermolecular interaction could predict the highest precision effectively. The symmetric molecules exhibit better reconfiguration capacity and smaller preaggregates than the asymmetric ones, which are helpful in stabilizing the drainage of foam films and construct high-precision patterns. Our results confirm the robustness of the bubble template to prepare molecular-scale patterns, verify the criticality of molecular symmetry to obtain the ultimate precision, and predict the application potential of high-precision organic patterns in hierarchical self-assembly and high-sensitivity sensors.

Femtosecond Laser Machining of Flexible Printed Circuit Boards

As the demand grows for high-density electronic components and highly integrated printed circuit boards, femtosecond laser micromachining provides unique opportunities for creating fine conductive tracks and patterns on flexible printed circuit boards (FPCBs) without the use of a mask. Here, the effects of femtosecond laser power and pulse frequency on micromachining depth, surface roughness and copper content of the machined zone were investigated, and optimum laser parameters, i.e., laser power 280 mW and pulse repetition frequency 39.5 kHz, were achieved with the help of a 3D optical profilometer and energy dispersive spectroscopy (EDS). On this basis, a single conductive track with varying widths and two parallel conductive tracks with different widths/spacings were micromachined on FPCBs without noticeable substrate damage. The results indicate that a single conductive line with a feature width as small as 25 µm can be achieved, and two parallel copper tracks can be created with no evidence of the presence of copper residues between the tracks when the pre-defined spacing is no less than 45 µm . In order to achieve high micromachining accuracy, look-up tables that correlate measured widths/spacing of conductive tracks with the pre-defined ones were built.besides, machining conductive tracks with 135 degree corner is possible and by selecting optimized processing parameters. Finally, a driving circuit for a display panel was micromachined on FPCBs using femtosecond laser, and an average micromachining accuracy of 0.67 μm was achieved. This work will be quite useful for creating high density and precision patterns on FPCBs using femtosecond laser.

Efficient Investigation of High‐Performance Perovskite Solar Cells Based on Shadow‐Mask Kits with Uniform Patterning and Antishadowing Capabilities

AbstractIn recent years, there has been increased research and rapid development in perovskite solar cells. Uniformity, repeatability, and reliability of electrode patterns formed by shadow‐mask technologies are factors that play an important role in efficient experimental studies for achieving high‐throughput samples and high‐performance devices. In this study, some new principles of mask design are investigated to overcome the drawbacks of conventional mask. High precision patterns are obtained by fabricating shadow‐masks with stainless steel plates via a photochemical etching process. An assembly concept design is proposed for shadow‐mask kits to improve versatility and avoid edge chamfer. The highly accurate active area and precise replication of the aperture patterns are obtained by improving the alignment between the samples and the mask patterns. The perovskite solar cell arrays are fabricated on a single substrate and a uniform performance is achieved due to the balanced distribution of electrodes. Thin shadow‐masks with smooth surfaces are employed to diminish the shadowing effect and a power conversion efficiency of 20.85% with a high fill factor of 81.6% is obtained in an inverted perovskite solar cell. The versatility and high quality of our shadow‐mask kits can further promote research in the area of thin‐film and photovoltaic technologies.

Coupled Electromagnetic and Reaction Kinetics Simulation of Super-Resolution Interference Lithography.

Inspired by the ability of super-resolved fluorescence microscopy to circumvent the diffraction barrier, two-color super-resolution interference lithography exploits nonequilibrium kinetics in materials to achieve large-area nanopatterning while using visible light. Periodic patterns with super-resolved features down to tens of nanometers have been demonstrated in thin films and monolayers. Extending these advances to the bulk nanopatterning of thick films requires a quantitative understanding of the time-dependent interactions of optical dynamics, including absorption, diffraction, and intensity modulation at two wavelengths, with the photoactivated and inhibited reaction kinetics. Here, we develop an efficient electromagnetic (EM) perturbation theory approach that facilitates for the first time fully coupled simulations of EM and chemical kinetics in two-color interference lithography. Applied to a spirothiopyran-functionalized photoresist system, these simulations show that diffraction and absorption effects are negligible (<0.1%) for depths up to 10 μm, and that tuning exposure time and intensities can lead to concentration contrast up to 80%. We investigate multiple exposure strategies to reduce the pitch of the line pattern including sequential exposures with different times to achieve uniform lines and multiplexed exposures with equal periods. This capability to rapidly and accurately predict the coupled optical and chemical dynamics facilitates the computational design of high-precision patterns in two-color interference lithography.

Roughness and wettability properties of plain and silica-coated copper surfaces textured with picosecond laser

Many recent studies have investigated the mechanism of wettability transition of laser-textured copper surfaces on different materials. Furthermore, several such studies have focused on approaches to accelerate wettability transition from hydrophilicity to hydrophobicity, such as temperature annealing and the use of chemical solutions. However, few researchers have focused on maintaining the initial hydrophilicity of laser-textured surfaces. This study presents a hybrid surface modification method involving chemical bath deposition and ultrafast laser. First, the selected copper substrates are modified using the sol-gel method through dip coating. Subsequently, the coated copper surfaces are irradiated with a picosecond laser. After laser texturing, bumpy structures are formed, and SiO2 nanoparticles can be sintered on the surfaces. Thus, the original hydrophilicity can be maintained, and the surface roughness can be enhanced simultaneously. By using this hybrid modification method, a heterogeneous surface with high-precision patterns can be obtained. Moreover, the mechanism of wettability transition of laser-textured copper surfaces with different laser fluences is discussed using the Wenzel and Cassie Baxter wetting model by analyzing the chemical composition and surface morphology of the treated surfaces.

A Novel Capacitive-Based Flexible Pressure Sensor Based on Stretchable Composite Electrodes and a Dielectric Elastomer With Microstructures

This paper presents a novel capacitive-based flexible pressure sensor that achieves a relatively high sensitivity with an outstanding linearity over a large measurement range, as well as low-pressure detection capacity. The proposed sensor mainly consists of two flexible conductive composite electrodes and one micro-structured elastomer with both pillars and cavities. The highly stretchable modal fabrics and carbon nanotubes conductive paste have been proposed for mixture to generate flexible capacitor electrode plates, and provide improved attributes in terms of excellent flexibility, conductivity, and air permeability. The micro-structured elastomers have been proposed and fabricated via demolding the silicone poured into the high-precision patterns that are produced by the 3D printing techniques. The exerted compression on assembled sensor prototype can induce decreased distance between electrode plates and increased dielectric constant due to the air deflation, leading to enhanced sensor sensitivity. By comparing three types of microstructures for the elastomers, it is found that the cubic-structure type can achieve a high sensitivity (232*10−4 kPa−1) with an excellent linearity of 99.4% in the measurement range of [0 kPa, 100 kPa]. The proposed flexible sensor has been prototyped, and several experiments have been performed for quantitative investigation and assessment. The grasp-and-release operations of a water-filled paper cup have been performed using a wearable glove embedded with two sensor prototypes, proving the effectiveness and feasibility of the proposed sensor design.

Influence of nano‐coated pigment ink formulation on ink‐jet printability and printing accuracy

Pigment ink was formulated with nano‐coated pigment dispersion, prepared via mini‐emulsion polymerization. To study the effect of nano‐coated pigment, surfactant and humectant on ink‐jet printability, the trajectory of droplets with different pigment ink composition was monitored. The effect of ink formulation on the accuracy of printing process of the pigment ink was discussed by study on line width and edge contour of printed patterns. Experimental results indicated that the additives and properties of the pigment ink had a great influence on droplet formation and precise positioning of the printed patterns. The optimal composition for the pigment ink as following: nano‐coated pigment dispersion was 20% w/w, surfactant (S‐465) was 1.5% w/w, humectant (diethylene glycol) was 30% w/w and defoamer (FB‐50) was 0.1% w/w. The prepared pigment ink exhibited excellent freeze–thaw, thermal and centrifugal stability. In addition, the optimal formula was beneficial to form a stable droplet and obtain high precision patterns.

Robust and thermoplastic hydrogels with surface micro-patterns for highly oriented growth of osteoblasts.

Biocompatible hydrogels with high strength, high precision patterns, and arbitrary 3D shapes are extremely desired soft platforms in the biomedicine fields. On the basis of the thermal-reversible sol-gel transition of agarose and the formation of nanofibers below 35 °C, a robust and thermoplastic hydrogel (TPG) was fabricated by in situ polymerization of acrylamide in the agarose matrix. The tensile fracture stress/strain values of the TPG were unexpectedly higher than those of both agarose and polyacrylamide hydrogels as a result of the double networks reinforced with nanofibers. The TPG could reversibly soften and harden by heating and cooling treatment, respectively, leading to an excellent mechanical recoverability and reprocessing ability. Thus, arbitrary 3D-shaped hydrogels and micro-patterns embossed on the TPG surface with a high resolution of 1 μm were constructed. The rigid TPG exhibited a remarkable affinity for the adhesion and proliferation of cells. In particular, the TPGs with microgrooves could highly guide the oriented growth of osteoblasts, showing potential applications in the field of tissue engineering.

Three-dimensional hologram-read-only memory duplication by nanoimprint lithography

Because the amount of multimedia data is continually increasing, there is growing demand for high-speed, large-capacity, read-only memory (ROM) to facilitate data distribution. Computer-generated hologram-ROM (CGH-ROM) has received considerable attention in relation to its potential to meet this rising demand. CGH-ROM requires a nanoscale-precision structure, as well as nanosteps. Because of its process simplicity, nanoimprint lithography (NIL) is a promising method for cost-effective fabrication of complex and high-precision patterns. The authors have demonstrated CGH-ROM duplication by ultraviolet NIL (UV-NIL) from a three-dimensional (3D) master mold fabricated by electron-beam lithography (EBL). The calculated depths of the CGH were converted into four tones to permit easy fabrication of the CGH while retaining a high diffraction efficiency. EBL using a spin-on glass and super-resolution technique with a postexposure bake was used to fabricate the 3D master mold. The developed depth was controlled by changing the EB exposure dose, with higher EB doses tending to produce deeper patterns. The pattern was duplicated by means of UV-NIL and the reconstruction image corresponded to the design pattern. Moreover, the authors have succeeded in fabricating a gray-scale multilevel CGH-ROM and in producing its reconstruction.

Study of Metals by Femtosecond Laser Processing for Electro-Optics Applications

Femtosecond laser (FS-laser) microstructuring of metals has become a promising tool because of its non-contact nature, which allows the micromachining and direct processing of materials with a minimized volume of heat-affected zone for electro-optics applications such as light emitting diodes (LED) and solar photovoltaic (PV) lighting. This study presents ultra-short pulse (10-15 sec) FS-laser processing. Through integrating the laser source, optical system and dynamic control modules, the materials of metals with micro-scale or nanoscale structures can be fabricated. In traditional processing such as semiconductor processing, development, exposure and etching necessitate expensive equipment and time-consuming tasks. With FS-laser processing, high-precision patterns are obtained, which will be a great benefit to keeping costs down. In this study, the wavelengths of FS-laser ablation are employed using visible and infrared light. To make a breakthrough in electro-optics processes, the CIGS thin-film of solar cells in metal process can be easily produced by the FS-laser. The ablation speed of the FS-laser for thin film layer CIGS solar cells can reach 2000 mm/s which is faster than the current Nd:YAG laser machine (~1000 mm/s). On the other hand, the minimum size of metal lines can be controlled to a value that is lower than 40 µm. Furthermore, green energy can be effectively developed for the future.

Research Progress of High-precision Patterns by Directly Inkjet Printing

High-precision patterns have aroused wide attention due to their important applications in high-performance op- tical/electrical devices. By virtue of easy and direct writing of desired patterns, high throughput and low-cost, inkjet printing has become one of the most promising candidates for the manufacture of patterns, compared with conventional approaches such as photolithography, microcontact printing. Various materials can be precisely deposited on target positions. As a pri- mary focus, improving the precision of printed patterns would greatly enhance the performance of the devices. So far, various approaches have been developed for improving the printing precision. Pattern resolution is limited by the volume of jetted droplet and the area of droplet spreading on substrate. Finer resolution can be achieved through reducing the deposition di- mension, i.e. optimization of the chemical composition of ink, chemical/physical modification of substrates, and improve- ment of printing apparatus. Besides, uniform deposition of functional materials is also essential for fabricating high-precision patterns and high-performance devices. Coffee ring is a common phenomenon during the drying process of droplets, which is generated due to the pinning three phase contact line (TCL) and the outward capillary flow in an evaporating droplet. Therefore, homogenous deposition without coffee ring effect can be realized by tuning the capillary flow in the droplet and controlling the movement of the TCL as the droplet evaporating. In this paper, we presented the recent research progress for achieving high-precision patterns by inkjet printing, including minimizing the deposition dimension to improve the resolution and avoiding the coffee ring effect to achieve high uniformity. These reports will probably promote the development of novel and facile method for high-precision inkjet printing. New trends and research perspectives were briefly discussed at the last section of this review.

Thermal inkjet printing for precision histological staining

Inkjet printing techniques may allow enhanced analysis of tissues. When the tissue available for processing is limited, for example, the amount of information obtained could be increased if different stains could be applied to discrete areas of the same tissue sections. In addition, it may be more desirable to stain an intact tissue rather than sections of tissue. Currently, there are very few methods by which many different stains can be applied in a controlled manner to a single section and/or single block of tissue. This paper presents a liquid deposition system, based on thermal inkjet technology, capable of precisely applying histological processing liquids to form high precision patterns at desired locations on both fixed tissues and cell monolayers. Four experiments were conducted to show the potential of single-drop reagent application, using aniline blue, toluidine blue, fluorescent probes, and an immunofluorescence antibody to create different patterns. Tissue type was shown to affect the overall quality of staining. The flexibility, resolution, and precision of this system have the potential to enable the formulation of new staining techniques to maximize the amount of information gleaned from a given tissue sample.

Numerical simulations of void linkage in model materials using a nonlocal ductile damage approximation

Experiments on the growth and linkage of 10 μm diameter holes laser drilled in high precision patterns into Al-plates were modelled with finite elements. The simulations used geometries identical to those of the experiments and incorporated ductile damage by element removal under the control of a ductile damage indicator based on the micromechanical studies of Rice and Tracey. A regularization of the problem was achieved through an integral-type nonlocal model based on the smoothing of the rate of a damage indicator D over a characteristic length L. The simulation does not predict the experimentally observed damage acceleration either in the case where no damage is included or when only a local damage model is used. However, the full three-dimensional simulations based on the nonlocal damage methodology do predict both the failure path and the failure strain at void linkage for almost all configurations studied. For the cases considered the critical parameter controlling the local deformations at void linkage was found to be the ratio between hole diameter and hole spacing.

Plastic Microfluidic Systems for High-Throughput Genomic Analysis and Drug Screening

Plastic Microfluidic Systems for High-Throughput Genomic Analysis and Drug Screening

Nonhomogeneous Pattern Formation in the Dissolution Processes of Novolak-Diazonaphthoquinone Resists

The development mechanisms of irradiated novolak-diazonaphthoquinone resists have been studied on the basis of the atomic force microscopy (AFM) data of resist surface images. The characteristic surfaces with large holes or island structures, that is, nonhomogeneous surfaces, have been observed at the exposure doses near the beginning of the film thickness reduction. The changes in the size of holes and island structures roughly correspond to the changes of cluster size estimated by percolation theory. From the dissolution pattern changes which depend on exposure dose, it is considered that an adequate exposure dose is indispensable for high-precision patterns and such an exposure dose determines the sensitivity of positive-type resists.

Crescimento diamétrico do pau-ferro (&lt;i&gt;Astronium balansae&lt;/i&gt;) em reflorestamento no município de São Sepé, RS.

A técnica de análise de tronco foi testada para avaliar o crescimento de pau-ferro, Astronium balansae, em povoamento implantado no município de São Sepé, RS e, atualmente, com 12 anos de idade, bem como descrever através de modelos matemáticos o crescimento diamétrico e os incrementos médio e corrente anual para árvores do estrato dominante e dominado. Os resultados demonstraram a pertinência da técnica de análise de tronco para descrever o crescimento passado da espécie, e permitiram desenvolver modelos de alta precisão e bom ajuste para descrever o incremento corrente e médio anual. No período de observação os dados indicam que o culmínio do incremento corrente anual ocorreu aos seis anos e do incremento médio anual aos dez anos para a árvore do estrato dominante, não devendo, entretanto, esta constatação ser tomada como definitiva antes da medição do crescimento em árvores de maior idade, o que permitirá verificar ou não a continuidade da queda das taxas de incremento. Não foi possível determinar na árvore dominada as idades de culmínio de incremento.