Micropattern Array Research Articles

Double-sided visible moiré magnifier with hierarchical microstructure

Conventional moiré magnifier suffers from high manufacturing cost and poor scalability due to the stringent requirement on alignment between the microfocusing element array and micropattern array (MPA). By superposition of the microreflective element array and MPA together to form hierarchical microstructure, not only the alignment can be done during mold fabrication process, which is easily scalable and compatible to semiconductor, but also the synthetically magnified image is visible as viewed from both front and back side. The investigation of the moiré magnifier with hierarchical microstructure unveils new imaging phenomenon in moiré imaging device, and thereby offers a facile and low-cost platform to address challenges to open up a potential avenue in micro-optic involved three-dimensional display or anti-counterfeiting applications.

Tissue-specific micropattern array chips fabricated via decellularized ECM for 3D cell culture

Multicellular three-dimensional (3D) in vitro models, such as cell spheroids and organoids, can significantly improve the viability, histomorphology, genotype stability, function and drug metabolism of cells [1–3]. In general, several culture methods of 3D models, including the hanging drop, microwell-mesh and hydrogel encapsulating methods, have difficulty building a standard mode and controlling the size and arrangement of cell spheroids or organoids, which could severely affect the authenticity and repeatability of experimental results [4]. Another key factor in 3D in vitro models is the extracellular matrix (ECM), which can determine cell viability, proliferation, differentiation, function, migration and organization [5]. In this study, micropattern array chips combined with decellularized ECM (dECM) not only provide tissue-specific ECM but also control the size and arrangement of 3D models.•Methods have been established to demonstrate the use of dECM as a bioink to generate dECM-coated micropattern array chips by microcontact printing.•The micropattern can limit cell growth and migration, and cells spontaneously assemble into cell spheroids with uniform size and orderly arrangement.

High-Linearity Flexible Pressure Sensor Based on the Gaussian-Curve-Shaped Microstructure for Human Physiological Signal Monitoring.

Flexible pressure sensors with high-performance show broad application prospects in health monitoring, wearable electronic devices, intelligent robot sensing, and other fields. Although flexible pressure sensors have made significant progress in sensitivity and detection range, most of them still exhibit strong nonlinearity, which leads to significant troubles in signal acquisition and thus limits their popularity in practical applications. It remains a serious challenge for the flexible pressure sensor to achieve high linearity while maintaining high sensitivity. Herein, a doped sensing membrane with a uniformly distributed Gaussian-curve-shaped micropattern array was developed using the micro-electromechanical systems (MEMS) process, and a flexible sensor structure with the doped film as the core was designed and constructed. The prototype sensor has a high sensitivity of 1.77 kPa-1 and a linearity of 0.99 in the full detection range of 20 Pa to 30 kPa. In addition, its excellent performance also includes fast response/recovery times (∼25/50 ms) and long-term endurance (>10,000 cycles at 15 kPa). The prototype sensor has been successfully demonstrated in human pulse monitoring, speech recognition, and gesture recognition. The 2 × 6 sensor array can detect the spatial pressure distribution. Thus, such a microstructure shape design will open a new way to fabricate a high-linearity pressure sensor for potential applications in health monitoring, human-machine interaction, etc.

Red-emitting micro PeLEDs for UHD displays by using capillary force lithography

Conventional techniques for fabricating micro-light-emitting diode (LED) pixel arrays for ultra-high definition (UHD) displays have drawbacks of high cost and complex processing. Furthermore, it is technically difficult to improve the display resolution using traditional patterning and deposition processes. As the size of the chips decreases to the microscale, there is an increase in the cost due to the additional transfer process, and inaccuracy of mechanical positioning during the repeated transfer process. To solve these problems, a micro-patterning method using capillary force lithography was introduced. Using this method, a 10 µm-scale CsPbBrxI3-x micro-pattern array was fabricated. Moreover, multi-ligand (NMABr0.7I0.3–DMPDAB–PDAB) and poly(ethylene oxide) (PEO) as a hydrophilic polymer were added to the perovskite precursors to control the heterogeneous nucleation and crystal growth during the patterning process. To demonstrate the feasibility of the 10 µm-scale micro-pattern array for the micro-perovskite LEDs (micro-PeLEDs), CsPbBrxI3-x–multi-ligand–PEO precursors were adopted. These micro-PeLEDs exhibited characteristic emission at 650.9 nm with a luminance of 688.4 cd m−2 and external quantum efficiency of 5.9% at 4 V.

Ordered micropattern arrays fabricated by lung-derived dECM hydrogels for chemotherapeutic drug screening.

AimsThis study aims to evaluate ECM-coated micropattern arrays derived from decellularization of native porcine lungs as a novel three-dimensional cell culture platform.MethodsECM derived from decellularization of native porcine lungs was exploited to prepare hydrogels. Then, dECM-coated micropattern arrays were fabricated at four different diameters (50, 100, 150 and 200 ​μm) using polydimethylsiloxane (PDMS). Two lung cancer cell lines, A549 and H1299, were tested on a dECM-coated micropattern array as a novel culture platform for cell adhesion, distribution, proliferation, viability, phenotype expression, and drug screening to evaluate the cytotoxicity of paclitaxel, doxorubicin and cisplatin.ResultsThe ECM derived from decellularization of native porcine lungs supported cell adhesion, distribution, viability and proliferation better than collagen I and Matrigel as the coated matrix on the surface. Moreover, the optimal diameter of the micropattern arrays was 100–150 ​μm, as determined by measuring the morphology, viability, proliferation and phenotype of the cancer cell spheroids. Cell spheroids of A549 and H1299 on dECM-coated micropattern arrays showed chemoresistance to anticancer drugs compared to that of the monolayer. The different distributions of HIF-1α, MCL-1 (in the center) and Ki-67 and MRP2 (in the periphery) of the spheroids demonstrated the good establishment of basal-lateral polarity and explained the chemoresistance phenomenon of spheroids.ConclusionsThis novel three-dimensional cell culture platform is stable and reliable for anticancer drug testing. Drug screening in dECM-coated micropattern arrays provides a powerful alternative to existing methods for drug testing and metabolic profiling in the drug discovery process.

Fabrication of Size-Controllable and Arrangement-Orderly HepG2 Spheroids for Drug Screening via Decellularized Liver Matrix-Derived Micropattern Array Chips.

Three-dimensional (3D) culture via micropattern arrays to generate cellular spheroids seems a promising in vitro biomimetic system for liver tissue engineering applications, such as drug screening. Recently, organ-derived decellularized extracellular matrix emerges as arguably the most biomimetic bioink. Herein, decellularized liver matrix (DLM)-derived micropattern array chips were developed to fabricate size-controllable and arrangement-orderly HepG2 spheroids for drug screening. The porcine DLM was obtained by the removal of cellular components and then ground into powder, followed by enzymolysis. DLM as a coating substrate was compared with collagen type I (Col I) and Matrigel in terms of biological performance for enhancing cell adhesion, proliferation, and functions. Subsequently, we used poly(dimethylsiloxane) (PDMS) to adsorb DLM as the bioink to fabricate micropattern array chips. The optimal shape and size of micropattern were determined by evaluating the morphology, viability, and functions of HepG2 3D cellular aggregates. In addition, drug-susceptibility testing (paclitaxel, doxorubicin HCl, and disulfiram) was performed on this novel platform. The DLM provided the tissue-specific microenvironment that provided suitable supports for HepG2 cells, compared to Col I and Matrigel. A circular micropattern with a diameter of 100 μm was the optimal processing parameter to rapidly fabricate large-scale, size-controllable, and arrangement-orderly HepG2 cellular aggregates with 3D spheroid’s shape and high cell viability. Drug screening testing showed that the effect of a drug could be directly demonstrated on-chip by confocal microscopy measuring the viability of spheroids. We provide a novel platform for the large-scale generation of HepG2 spheroids with uniform size and arrangement, thus bringing convenience, reducing error, and increasing reproducibility for a rapid drug discovery by fluorescence quantitative analysis. This methodology may be possible to apply in advancing personalized medicine and drug discovery.

Multifunctional Printable Micropattern Array for Digital Nucleic Acid Assay for Microbial Pathogen Detection

The digital nucleic acid assay is a precise, sensitive, and reproducible method for determining the presence of individual target molecules separated in designated partitions; thus, this technique can be used for the nucleic acid detection. Here, we propose a multifunctional micropattern array capable of isolating individual target molecules into partitions and simultaneous on-site cell lysis to achieve a direct DNA extraction and digitized quantification thereof. The multifunctional micropattern array is fabricated by the deposition of a copolymer film, poly(2-dimethylaminomethyl styrene-co-hydroxyethyl methacrylate) (pDH), directly on a microfluidic chip surface via the photoinitiated chemical vapor deposition process, followed by hydrophobic microcontact printing (μCP) to define each partition for the nucleic acid isolation. The pDH layer is a positively charged surface, which is desirable for the bacterial lysis and DNA capture, while showing exceptional water stability for more than 24 h. The hydrophobic μCP-treated pDH surface is stable under aqueous conditions at a high temperature (70 °C) for 1 h and enables the rapid and reliable formation of thousands of sessile microdroplets for the compartmentalization of an aqueous sample solution without involving bulky and costly microfluidic devices. By assembling the multifunctional micropattern array into the microfluidic chip, the isothermal amplification in each partition can detect DNA templates over a concentration range of 0.01-2 ng/μL. The untreated bacterial cells can also be directly compartmentalized via the microdroplet formation, followed by the on-site cell lysis and DNA capture on the compartmentalized pDH surface. For Escherichia coli O157:H7, Salmonella enteritidis, and Staphylococcus aureus cells, cell numbers ranging from 1.4 × 104 to 1.4 × 107 can be distinguished by using the multifunctional micropattern array, regardless of the cell type. The multifunctional micropattern array developed in this study provides a novel multifunctional compartmentalization method for rapid, simple, and accurate digital nucleic acid assays.

Altering the surface wettability of copper sheet using overlapping laser shock imprinting

Overlapping laser shock imprinting (LSI) is proposed to alter the surface wettability of copper sheet. By using a micro-die with rough concave texture, under the action of laser shock waves, multiscale surface microstructures can be accurately fabricated. The homogeneity of the micro-pattern array under different overlap rates were investigated. The radial expansion effect can reduce the inhomogeneity, but the shock pressure induced by the radial expansion effect in the non-irradiated area is weaker than that in laser irradiated area. Observed contact angle result is in accord with theoretical Cassie-Baxter mode, and it increases first and then tends to be stable when the number of laser pulse ranges from 2 to 6. Multiscale surface microstructures can be observed in 4 and 6 laser pulses cases. LSI can reduce the surface free energy by decreasing its polar component, and it sharply decreases first and then tends to be stable when the number of laser pulse ranges from 2 to 6. The grain size of protruding feature decreases with laser pulse numbers. And nano-scale grains are observed on the surface layer, which is caused by the material flowing on the rough surface of micro-die. The nano-indentation tests indicated that mechanical properties are enhanced.

Multifunctional interlocked e-skin based on elastic micropattern array facilely prepared by hot-air-gun

Electronic skin (e-skin) based on elastic piezoresistive sensor is considered to be one of the most important components for future wearable electronic devices, whose performances can be substantially improved by shaping patterned surface. However, most patterned surfaces are generally fabricated via some tedious methods. Obviously, it is still a huge challenge to realize high sensing performance via facile fabrication process. Here, an efficient but facile method named hot-air-gun assisted preparation is proposed, which enable quasi-hemispherical micropatterned array to be directly fabricated on the single-walled carbon nanotubes (SWCNTs)/thermoplastic polyurethane (TPU) film. The interlocked micropatterns can significantly improve the sensing performance of the as-prepared e-skin based on such micropatterned film, endowing it with very fast response time (<46 ms), wide working range (0.055–254.8 kPa) and excellent durability (>20000 cycles). Interestingly, the interlocked e-skin exhibits multifunction to simultaneously discriminate pressure–temperature stimuli. Moreover, it can monitor a variety of human physiological signals (e.g., arterial pulse waveform, voice recognition and human breathing behavior), indicating a promising application in human–machine interaction. Furthermore, the as-prepared interlocked e-skin could be connected to a wireless transmitter for wireless monitoring respiratory rates. Considering the facile preparation process and the low-cost raw materials, this approach can be easily scaled up for practical production.

레이저 쇼크 패터닝을 통한 표면 텍스처링이 알루미늄과 강 접촉면의 마찰특성에 미치는 영향

In this study, a laser shock surface patterning process was applied to effectively transfer a micro-pattern array to an aluminum specimen. The effect of surface texturing on the tribological properties of aluminum and steel contact surfaces was investigated. In dry conditions, the friction coefficient of the contact surface could be significantly reduced through surface texturing. However, as the contact load increased, the amount of wear debris collected in the cavity became too large, and the influence of the micro-pattern on the frictional force decreased. In lubricated conditions, surface texturing significantly reduced the average friction coefficient and its variation. The effect of surface texturing became prominent in high contact load conditions due to the increase in hydrodynamic effects. Further studies considering the pattern geometry, loading conditions, and properties of the lubricant are needed to quantitatively model the coefficient of friction.

Using the Patterned Microarray Culture to Obtain Gene-Editing Monoclonal Cells

Genetically modified pigs are the first choice for xenotransplantation research, but there have been problems with monoclonal screening of edited cells before nuclear transfer. Our objective was to get a novel strategy to quickly obtain monoclonal cells with low damage by microarray and to produce efficient gene-editing monoclonal cells in batches. Micropattern array printing technology was introduced to limit only a single cell was adhered on a micropattern substrate, and after 4 days of culture, the single cell grew into a monoclonal cell sphere and then came off from the bottom of the petri dish automatically. After sequencing, the results showed that a single cell is confined to a micropattern and grows into a sphere of monoclonal cells.

Dynamic effect in the moiré magnifier by using the weak domain transformation

The design of an image with dynamic effect usually adopts an interlacing strategy, but it suffers from the crosstalk between the neighboring images. Here, by introduction of the weak domain transformation to the micro pattern array (MPA), striking motion effects are realized with no crosstalk. A complete theoretical model based on both the moiré and fix point theorem is developed for interpretation of the kinetics. A microlens array-based moiré magnifier is fabricated to demonstrate the visually striking motion effect. The moiré magnifier is of primary interest for a wide variety of applications in appealing decoration, information encryption, and displacement measurement, etc.

Superposition of micropattern and microlens arrays for improved dynamic moiré pattern

Layers of microlens array (MLA) and micropattern array (MPA) are integrated on a layer of polyester film, with the aim to give rise to a special dynamic pattern which can be observed without any visual facilities. In this paper, we propose an improved approach for obtaining a presentation of an individual dynamic moiré pattern rather than dynamic moiré patterns in an array. The improved dynamic moiré pattern can be amplified without size limitation and has different dynamic effects from the traditional dynamic moiré pattern, as it will appear and disappear with variation of the viewing angle. The principle of designing every elemental unit of the MPA is described. The differences between the improved method and the traditional method are compared, and how the improved dynamic moiré pattern works is explained in detail. The formulae describing the relationship between parameters of the improved dynamic moiré pattern and its microstructure are derived. In addition, relative experiments are conducted, and an improved dynamic moiré pattern of the expected size are achieved and validated. This microstructural device on film has potential applications in document security, packaging, and authentication.

Analysis and optimization of the Glass pattern realized by a microlens array.

It is well known that the superposition of two identical random dot patterns may give rise to a particular form of moiré effect known as a Glass pattern. By integrating a microlens array and a micropattern array and applying a small geometrical transformation, it is possible to show the parallactic or the orthoparallactic motion effect when varying the viewing angle. In this paper, we study the effect of the structural parameters of a Glass pattern optical system on its image quality. The position of each elemental pattern in the micropattern array is derived based on a revised model that considers the finite observation distance. The image quality is evaluated by the ray analysis on the observation plane and the reconstructed image plane. Rays from different pixels of the micropattern array are evaluated by the spot size. The depth of the Glass pattern in image space is also analyzed. In addition, a Glass pattern optical system is simulated and optimized by ZEMAX software. An optimal result is obtained that validates the theoretical analysis. Our study can find potential application for designing Glass pattern optical systems or optimization of those imaging systems based on microlens arrays.

The homogeneity of multi-textured micro-pattern arrays in a laser shock surface patterning process and its effect on the surface properties of aluminum alloy

In this study, a laser shock surface patterning process was performed to effectively implement hundreds of micro-patterns on a metallic surface through a single laser beam irradiation. Micro-pattern arrays of rectangular, hexagonal, circular, and mesh shapes of various sizes were successfully transferred to the workpiece, and a multi-textured surface structure was realized. In order to improve the homogeneity of the micro-pattern array, it was most effective to increase the thickness of the ablation layer. In the case of the thicker ablation layer, it seems that more uniform pressure was transferred to the material because the ablation layer was in a relatively rigid state due to the reduced level of self-deformation. Since the laser shock surface patterning process exerts a strong shock loading along with plastic deformation on the material surface, the hardness value increased mainly around the area subjected to the shock load. The better the homogeneity of the micro-pattern array, the less the deviation in the hardness value. Therefore, it is important to ensure micro-pattern uniformity in order to achieve uniform surface properties. Changes in the contact angle were also observed under various process conditions. After surface patterning, the contact angle increased as the amount of air trapped in the bar region increased. As the laser intensity increased, it was observed that the geometric surface changes were sharp, and the surface structure changed. As a result, the contact between the air and the water droplets decreased, and the contact angle decreased.

Elemental pattern capture method for realizing Glass moiré patterns

Microlens array and micropattern array are integrated on a sheet of polyester film aiming to give rise to a Glass moiré pattern, which can be observed without any visual facilities. In this paper, we propose an elemental pattern capture method for obtaining a special presentation of an individual Glass moiré pattern rather than moiré patterns displayed in an array. The Glass moiré pattern will appear and disappear with the viewing angle varying. The pickup process and reconstruction process are introduced in detail. Besides, optimization method has been proposed to solve the cross-interference. In addition, we put forward a way to control the viewing angle in which the moiré pattern appears. Experiments are carried out to verify the validity of our method. This moiré phenomenon shows a good application prospect in document security and authentication. The elemental pattern capture method can find potential applications in integral imaging.

Performance evaluation of laser shock micro-patterning process on aluminum surface with various process parameters and loading schemes

In this study, a laser shock micro-patterning process was used to indirectly transfer laser energy to materials and to efficiently fabricate a microscale pattern array on the material surface. Various pressure transfer methods of laser shock waves were investigated and the optimal process condition was determined. The method of pressurizing the workpiece using the ablation layer was considered most appropriate for achieving the desired depth and homogeneity of the micro-patterns. The method of pressing the grid mold using the ablation layer was very effective in minimizing the shape deviation between the patterns. However, excessive deformation of this layer resulted in a large loss of depth. The method of creating a micro-pattern array through high-speed collisions of metal flyers with the workpiece played a minor role in the laser shock micro-patterning process. This resulted from the considerable energy loss and concentration of the impact in the central region of the flyer. The effect of the ablation-layer thickness and the insertion of the hyper-elastic material on the surface patterning performance was investigated. When a thin ablation layer was used, the energy loss was reduced and, hence, the depth of the micro-pattern increased. However, when the hyper-elastic material was inserted, reductions in the pressure transfer efficiency prevented improvements in the depth and homogeneity of the patterns. Hardness measurements of the patterned surface revealed that the hardness increased, due to the influence of the laser shock load, even in the region indirectly exposed to the laser shock wave. Furthermore, the hardness value increased with increasing depth of the micro-pattern.

Properties of dynamic image displacements based on microstructure.

The superposition structure of dynamic moiré images contains a layer of micropattern array and a corresponding layer of microlens array. Dynamic moiré images can be observed without special eyeglasses and will shift with variation of the viewing angle. In this work, it is described as a presentation of a variety of the moiré. We chiefly investigate the motion effects of dynamic moiré images. Analytical models to describe the structures and methods to evaluate the displacement of dynamic moiré images are proposed. Experiments are conducted to validate the formula of the displacement. The results of this study are helpful to design dynamic moiré images, which can be applied for potential applications in anti-counterfeiting films, packaging, and authentication.

Dynamic patterns based on the superposition of micropattern array and microlens array

Dynamic patterns have been studied theoretically and experimentally in this work. The microstructure consists of a base layer made up of micropattern array, and a superposed revealing layer made up of microlens array. Dynamic patterns will be observed directly on the revealing layer without visual facilities. When the viewing angle changes, displacement of dynamic patterns is produced. This technology is compared with traditional moiré techniques. In addition, analytical models to describe its structures are derived based on a vector method. There is a good agreement between the theoretical and experimental results, which indicates this study is helpful to design various kinds of dynamic patterns and dynamic effects, and this technology can be applied for many applications, especially in anti-counterfeiting field.

Design and fabrication of ultrathin lighting responsive security device based on moiré imaging phenomenon

Security authentication of high- and low-value products is a pressing issue. Security technologies should be upgraded before they are counterfeited. In this study, an ultrathin lighting responsive moiré imaging device, which is different from traditional security device is developed for security authentication. Some interesting lighting responsive moiré imaging phenomena including light-activated three-dimensional floating imaging and light-controlled image transformation have been developed as covert security features for advanced authentication. These security features can be verified instantly using a point light source such as a white light-emitting diode configured in a smart phone. A compact defocus optical structure consisting of a micro lens-mirror array (MLMA) and a micro-pattern array is designed to fabricate the lighting responsive moiré imaging device. The structure makes the device ultrathin, which enables the easy integration of the device. The MLMA also overcame the difficulty in the fabrication of high numerical aperture micro-lens array required in traditional moiré imaging system. Flexible devices with 78-μm thickness were fabricated by photolithography, imprinting, and gravure-like techniques. Such thin device allows its potential integration with banknotes, currency, or other valuable documents/products.