Fabrication Of Micropatterns Research Articles

Formation of interfaces responsive and adaptive to environment via the sol-gel method

Smart devices, such as soft robots, artificial organs, and soft actuators, require materials that adapt their morphologies and properties in response to their environment. These materials can be obtained through the composition of different types of materials that exhibit different responses to environmental stimuli, arranged in a rational spatial configuration. We achieved unique responsive materials by forming interfaces and surfaces of appropriate materials using the sol–gel method. In recent decades, we have proposed the use of wrinkles and nano-brushes on sol–gel-derived materials for various sophisticated applications, such as micropattern fabrication, wettability control, and linear actuators for size-selective transportation. This account introduces environment-responsive materials with rational interfaces via the sol–gel method, particularly those characterized by surface morphology.Graphical Materials with unique environmental responsiveness such as micropattern fabrication, wettability control, and linear actuating can be achieved by forming interfaces and surfaces using the sol–gel method.

Rapid and versatile, micro-patterning and functionalization of complex structures on ultra-thin and flexible polymeric substrates

Microscale patterning on flexible substrates is important in many applications such as in wearable sensors and microfluidics-based diagnostics, therefore low-cost fabrication methods which are scalable and amenable to mass production have attracted the interest of many companies and research groups. Dry film resists (DFRs) are commercially available materials with properties compatible with their implementation on flexible substrates to cover a wide range of applications, which also offer environmental and sustainability benefits due to the low waste generation compared to the liquid resists. However, there are limited detailed reports in the literature regarding the use of DFRs for the fabrication of microfluidic channels or other micropatterns (i.e., posts) on thin and flexible substrates. Herein we present in detail the fabrication of: a) microfluidic channels of width ranging from 50 μm up to 800 μm, and depth ranging from 30 μm up to 270 μm and b) square posts 80 μm × 80 μm in size and 30 μm in height. Particularly, our method enables the fabrication of ultra-deep microchannels (depth > 250 μm), highly ordered post arrays over large area (appr. 60 cm2), as well as complex designs with hierarchical scale features (80 μm posts inside 800 μm microchannels or micro-nanotexturing inside microchannels) on ultra-thin flexible substrates. To demonstrate the versatility of the method, three different DFRs were used on ultra-thin (30 μm), flexible, single-sided copper-clad polyimide substrates. It is also demonstrated that DFRs can be effectively modified using plasma etching to tune the surface wetting properties towards applications such as pumpless capillary action, where such functionality is required.

High‐Quality Micropattern Printing by Complex‐Amplitude Modulation Holographic Femtosecond Laser

AbstractHolographic femtosecond laser printing technology is widely used in the fabrication of micropatterns because of its high efficiency and flexibility. However, speckle noise and energy fluctuations limit the quality of the printed structure. In this study, an improved complex‐amplitude modulation holographic femtosecond laser printing method for high‐quality micropattern fabrication is proposed. The holographic light field is divided into a signal area and a surrounding noise area. To improve laser uniformity, phase modulation is applied in the signal region to eliminate the speckle noise caused by unconstrained phase interference, and weighted amplitude modulation is introduced in the signal area to improve the calculation accuracy. To precisely control laser energy density, weighted energy efficiency modulation is introduced in the noise region to disperse the energy that exceeds the material damage threshold. Under the synergistic control of laser uniformity and energy density, high‐quality micro‐pattern structures are printed efficiently. A high‐quality millimeter‐sized multifocal zone plate with micron accuracy is fabricated with the splicing printing method, demonstrating the potential of micropattern processing and the fabrication of functional devices such as binary optics.

GelMA micropattern enhances cardiomyocyte organization, maturation, and contraction via contact guidance.

Cardiac tissue engineering has emerged as a promising approach for restoring the functionality of damaged cardiac tissues following myocardial infarction. To effectively replicate the native anisotropic structure of cardiac tissues in vitro, this study focused on the fabrication of micropatterned gelatin methacryloyl hydrogels with varying geometric parameters. These substrates were evaluated for their ability to guide induced pluripotent stem cell-derived cardiomyocytes (CMs). The findings demonstrate that the mechanical properties of this hydrogel closely resemble those of native cardiac tissues, and it exhibits high fidelity in micropattern fabrication. Micropatterned hydrogel substrates lead to enhanced organization, maturation, and contraction of CMs. A microgroove with 20-μm-width and 20-μm-spacing was identified as the optimal configuration for maximizing the contact guidance effect, supported by analyses of nuclear orientation and F-actin organization. Furthermore, this specific micropattern design was found to promote CMs' maturation, as evidenced by increased expression of connexin 43 and vinculin, along with extended sarcomere length. It also enhanced CMs' contraction, resulting in larger contractile amplitudes and greater contractile motion anisotropy. In conclusion, these results underscore the significant benefits of optimizing micropatterned gelatin methacryloyl for improving CMs' organization, maturation, and contraction. This valuable insight paves the way for the development of highly organized and functionally mature cardiac tissues in vitro.

Development of Electrochemical Microtextured Cell for Fabrication of Complex Micropattern

Introduction: This paper highlights the representative patents related to the application of maskless electrochemical micromachining (EMM) using microtextured tools and developed cells under electrolysis conditions for the generation of high-quality complex patterns, i.e., cascade micropattern on stainless steel. background: Electrochemical Microtextured Cell Method: To acquire high accuracy level, the workpiece and tools are fixtured properly in the developed microtextured cell, and a developed vertical cross-flow system is utilized for the generation of a precise cascade micropattern. An electrochemical microtextured cell is designed and developed inexpensively for the fabrication of high-quality complex micropatterns. The eco-friendly combined electrolyte of NaNO3 and NaCl is employed for precise micro texturing. Result: The consequence of predominant input factors, i.e., IEG, voltage, and flow rate, are explored on machining rate, precision, depth, and surface finish during complex micro-texturing using developed microtextured cells. The complex microtextured tool is fixtured in tool holding device in a developed microtextured cell and fabricates nineteen precise complex micropatterns. Conclusion: An effort has been made to find suitable input factors for the generation of precise complex micropatterns.

Optimizing broadband antireflection with Au micropatterns: a combined FDTD simulation andtwo-beam LIL approach.

Broadband antireflection (AR) is highly significant in a wide range of optical applications, and using a gold (Au) micropattern presents a viable method for controlling the behavior of light propagation. This study investigates a novel, to the best of our knowledge, methodology to achieve broadband AR properties in Au micropatterns. It employed the three-dimensional finite-difference time-domain (FDTD) method to simulate and optimize the design of micropatterns. In contrast, the fabrication of Au micropatterns was carried out using two-beam laser interference lithography (LIL). The fabricated Au micropatterns were characterized by a scanning electron microscope (SEM) and spectroscope to validate their antireflection and transmission properties and evaluate their performance at various wavelengths. The optimized Au micropatterns had a high transmittance rating of 96.2%. In addition, the device exhibits a broad-spectrum antireflective property, covering wavelengths ranging from 400 to 1100nm. The simulation data and experimentally derived results show comparable patterns. These structures can potentially be employed in many optical devices, such as solar cells and photodetectors, whereby achieving optimal device performance reduced reflection and enhanced light absorption.

Fabrication of Micropatterns of Aligned Collagen Fibrils.

Many tissues in vivo contain aligned structures such as filaments, fibrils, and fibers, which expose cells to anisotropic structural and topographical cues that range from the nanometer to micrometer scales. Understanding how cell behavior is regulated by these cues during physiological and pathological processes (e.g., wound healing, cancer invasion) requires substrates that can expose cells to anisotropic cues over several length scales. In this study, we developed a novel method of fabricating micropatterns of aligned collagen fibrils of different geometry onto PDMS-coated glass coverslips that allowed us to investigate the roles of topography and confinement on corneal cell behavior. When corneal cells were cultured on micropatterns of aligned collagen fibrils in the absence of confinement, the degree of cell alignment increased from 40 ± 14 to 82 ± 5% as the size of the micropattern width decreased from 750 to 50 μm. Although the cell area (∼2500 μm2), cell length (∼160 μm), and projected nuclear area (∼175 μm2) were relatively constant on the different micropattern widths, cells displayed an increased aspect ratio as the width of the aligned collagen fibril micropatterns decreased. We also observed that the morphology of cells adhering to the surrounding uncoated PDMS was dependent upon both the size of the aligned collagen fibril micropattern and the distance from the micropatterns. When corneal cells were confined to the micropatterns of aligned collagen fibrils by a Pluronic coating to passivate the surrounding area, a similar trend in increasing cell alignment was observed (35 ± 10 to 89 ± 2%). However, the projected nuclear area decreased significantly (∼210 to 130 μm2) as the micropattern width decreased from 750 to 50 μm. The development of this method allows for the deposition of aligned collagen fibril micropatterns of different geometries on a transparent and elastic substrate and provides an excellent model system to investigate the role of anisotropic cues in cell behavior.

Lipidure-based micropattern fabrication for stereotyping cell geometry

Cell autonomous behaviors such as migration and orchestration of cell polarity programs are required for physiological tissue formation. Micropatterns are cell-adhesive shapes that confine cell(s) to a user defined geometry. This biophysical confinement allows researchers to standardize the cell shape, and in doing so, stereotype organelle and cytoskeletal systems that can have an arbitrary organization. Thus, micropatterning can be a powerful tool in interrogation of polarity programs by enforcing a homogenous cell shape and cytoskeletal organization. A major drawback of this approach is the equipment and reagent costs associated with fabrication. Here, we provide a characterization of a compound called Lipidure (2-Methacryloyloxy ethyl phosphorylcholine) that is up to 40X less expensive than other cell repulsive coating agents. We found that Lipidure is an effective cell-repulsive agent for photolithography-based micropattern fabrication. Our results demonstrate that Lipidure is sensitive to deep UV irradiation for photolithography masking, stable in both benchtop and aqueous environments, non-toxic in prolonged culture, and effective at constraining cell geometry for quantification of cytoskeletal systems.

Fabrication of micro patterns on BaTiO3:Er3+/Yb3+ perovskite films by femtosecond laser micromachining

Femtosecond lasers currently show much promise as potential sources for the fabrication of optical and photonic devices, displaying high performance due to their high resolution, excellent geometric flexibility, and low collateral damage. In particular, devices displaying high performance based on BaTiO3:Er3+/Yb3+ (BTEY) films have been widely investigated, promising for the innovation of perovskite patterning applications. Herein, we fabricated BTEY perovskite films by spin coating at room temperature. XRD pattern and Raman spectroscopy analysis of the BTEY films revealed a tetragonal crystal structure. The study of Williamson-Hall's method calculated the strain and crystallite size for the BTEY film. Different parameters in the exploiting cylindrical focusing of an fs-laser were adopted to modulate the crater cavity of patterning, which gives the opportunities to evaluate their impact on the energy ablation threshold (Eth). It was found that cavity radius is proportional to the energy cross-section, thus providing wide range dependence of damaged spot size versus pulse energy. The Eth was measured using Liu's method, determining a value of Eth that decreased from 33.4 nJ to 22.4 nJ when the number of applied laser pulses per spot increased. It is found that the number of pulses per spot low possesses the best performance, successfully producing highly uniform patterning. Moreover, the evolution with the number of pulses also revealed changes in the surface morphology of the crater cavity via AFM and scanning confocal fluorescence microscopy (SCFM) analysis. These results are crucial for determining the Eth required to damage the material, understating the driving mechanism of formations of cavity profile surfaces, and changes in their optics properties in the edges owing to the balling effects and structural defects.

High-Resolution Patterning of Perovskite Quantum Dots via Femtosecond Laser-Induced Forward Transfer

High-resolution patterning of perovskite quantum dots (PQDs) is of significant importance for satisfying various practical applications, including high-resolution displays and image sensing. However, due to the limitation of the instability of PQDs, the existing patterning strategy always involves chemical reagent treatment or mask contact that is not suitable for PQDs. Therefore, it is still a challenge to fabricate high-resolution full-color PQD arrays. Here, we present a femtosecond laser-induced forward transfer (FsLIFT) technology, which enables the programmable fabrication of high-resolution full-color PQD arrays and arbitrary micropatterns. The FsLIFT process integrates transfer, deposition, patterning, and alignment in one step without involving a mask and chemical reagent treatment, guaranteeing the preservation of the photophysical properties of PQDs. A full-color PQD array with a high resolution of 2 μm has been successfully achieved. We anticipate that our facile and flexible FsLIFT technology can facilitate the development of diverse practical applications based on patterned PQDs.

Asymmetric Wettability Mediated Patterning of Single Crystalline Nematic Liquid Crystal and P-N Heterojunction Toward a Broadband Photodetector.

The well aligned and precise patterning of liquid crystals (LCs) are considered as two key challenges for large-scale and high-efficiency integrated optoelectronic devices. However, owing to the uncontrollable liquid flow and dewetting process in the conventional techniques, most of the reported research is mainly focused on simple sematic LCs, which are composed of terthiophenes or benzothieno[3, 2-b][1] benzothiophene backbone; only a few works are carried out on the complicated LCs. Herein, an efficient strategy was introduced to control the liquid flow and alignment of LCs and realized precise and high-quality patterning of A-π-D-π-A BTR, based on the asymmetric wettability interface. Through this strategy, the large-area and well-aligned BTR microwires array was fabricated, which exhibited highly ordered molecular packing and improved charge transport performance. Furthermore, the integration of BTR and PC71BM was achieved to manufacture uniform P-N heterojunction arrays, which still possessed highly ordered alignment of BTR. On the basis of these aligned heterojunction arrays, the high-performance photodetector exhibited an excellent responsivity of 27.56 A W-1 and a specific detectivity of 2.07 × 1012 Jones. This research not only provides an efficient strategy for the fabrication of aligned micropatterns of LCs but also gives a novel insight for the fabrication of high-quality micropatterns of the P-N heterojunction toward integrated optoelectronics.

Modification of nickel micropatterns for sensor-active applications from deep eutectic solvents

In this work, we proposed a rapid single-stage laser-induced fabrication of bimetallic micropatterns on the oxide glass surface using deep eutectic solvents (DESs) consisting of choline chloride, citric acid along with nickel, copper and cobalt acetates as metallization solutions. The resulting bimetallic micropatterns were tested as working electrodes for non-enzymatic determination of dopamine. The linear range for dopamine detection was found to be 1–500 µM, with sensitivity of 340.4 µA mM− 1 and 615.2 µA mM− 1 and detection limit of 0.36 µM and 0.51 µM for Ni-Cu and Ni-Co sensor, respectively. For the first time, bimetallic Ni-Cu and Ni-Co structures have been obtained from DESs for high-performance dopamine detection with great potential for further application in non-enzymatic sensing and biosensing.

Developing an Effective and Durable Film for Marine Fouling Prevention from PDMS/SiO2 and PDMS/PU with SiO2 Composites.

Polymer film coating with a highly hydrophobic surface property is a practical approach to prevent fouling of any structures in the marine environment without affecting marine microorganisms. The preparation of a polymer coating, from a simple and easy method of solution blending of hydrophobic polydimethylsiloxane elastomer and hydrophilic polyurethane with SiO2, was carried out in this study, with the aim of improving characteristics, and the coating demonstrated economic feasibility for antifouling application. Incorporation of SiO2 particles into PDMS and PDMS/PU polymer film improved mechanical properties of the film and the support fabrication of micropatterns by means of a soft lithography process. Observations from field emission scanning electron microscope (FESEM) of the PDMS/SiO2 composite film revealed a homogeneous morphology and even dispersion of the SiO2 disperse phase between 1–5 wt.%. Moreover, the PDMS film with 3 wt.% loading of SiO2 considerably increased WCA to 115.7° ± 2.5° and improved mechanical properties by increasing Young’s modulus by 128%, compared with neat PDMS film. Additionally, bonding strength between barnacles and the PDMS film with 3 wt.% of SiO2 loading was 0.16 MPa, which was much lower than the bonding strength between barnacles and the reference carbon steel of 1.16 MPa. When compared to the previous study using PDMS/PU blend (95:5), the count of barnacles of PDMS with 3 wt.% SiO2 loading was lower by 77% in the two-week field tests and up to 97% in the eight-week field tests. Subsequently, when PDMS with 3 wt.% SiO2 was further blended with PU, and the surface modified by the soft lithography process, it was found that PDMS/PU (95:5) with 3 wt.% SiO2 composite film with micropatterns increased WCA to 122.1° ± 2.9° and OCA 90.8 ± 3.6°, suggesting that the PDMS/PU (95:5) with 3 wt.% SiO2 composite film with surface modified by the soft lithography process could be employed for antifouling application.

One-Stage Femtosecond Laser-Assisted Deposition of Gold Micropatterns on Dielectric Substrate.

In this study, a simple one-stage laser-assisted metallization technique based on laser-induced backside wet etching and laser-induced chemical liquid-phase deposition is proposed. It allows for the fabrication of gold micropatterns inside the laser-written trace on a glass substrate. The reduction and deposition of gold inside and outside the laser-ablated channel were confirmed. The presence of Au nanoparticles on the surface of the laser-written micropattern is revealed by atomic force microscopy. The specific resistivity of the gold trace formed by ultrafast light-assisted metal micropatterning on a dielectric glass substrate is estimated as 0.04 ± 0.02 mΩ·cm. The obtained results empower the method of the selective laser-assisted deposition of metals on dielectrics and are of interest for the development of microelectronic components and catalysts, heaters, and sensors for lab-on-a-chip devices.

Simulation of Cone-Jet and Micro-Drip Regimes and Printing of Micro-Scale Patterns on PET Substrate.

The fabrication of various micro-patterns on polymer insulating substrates is a current requirement in micro-electromechanical system (MEMS) and packaging sectors. In this paper, we use electrohydrodynamic jet (E-Jet) printing to create multifaceted and stable micro-patterns on a polyethylene terephthalate (PET) substrate. Initially, simulation was performed to investigate optimized printing settings in phase field physics for the usage of two distinct functional inks. A series of simulation experiments was conducted, and it was determined that the following parameters are optimised: applied pressure of 40 kPa, high pulse voltage of 1.95 kV, low dc voltage of 1.60 kV, duty cycle of 80%, pulse frequency of 60 Hz, printing height of 0.25 mm, and printing speed of 1 mm/s. Then, experiments showed that adjusting a pressure value of 40 kPa and regulating the SEMICOSIL988/1 K ink to print micro-drops on a polymer substrate with a thickness of 1 mm prevents coffee staining. The smallest measured droplet size was 200 μm. Furthermore, underfill (UF 3808) ink was driven with applied pressure to 50 kPa while other parameters were left constant, and the minimum size of linear patterns was printed to 105 μm on 0.5-mm-thick PET substrate. During the micro-drip and cone-jet regimes, the consistency and diameter of printed micro-structures were accurately regulated at a pulse frequency of 60 Hz and a duty cycle of 80%.

Micro-pattern Fabrication of Amorphous Alloy by Laser Beam Machining

Micro-pattern Fabrication of Amorphous Alloy by Laser Beam Machining

Optimized Micro-Pattern Design and Fabrication of a Light Guide Plate Using Micro-Injection Molding.

This study examined the uniformity of illuminance field distributions of light guide plates (LGPs). First, the authors designed microstructural patterns on the surface of an LGP. Then, a mold of the LGP with the optimal microstructural design was fabricated by a photolithography method. Micro-injection molding (μIM) was used to manufacture the molded LGPs. μIM technology can simultaneously manufacture large-sized wedge-shaped LGPs and micro-scale microstructures. Finally, illuminance values of the field distributions of the LGPs with various microstructures were obtained through optical field measurements. This study compared the illuminance field distributions of LGPs with various designs and structures, which included LGPs without and those with microstructure on the primary design and the optimal design. The average illuminance of the LGP with microstructures and the optimal design was roughly 196.1 cd/m2. Its average illuminance was 1.3 times that of the LGP without microstructures. This study also discusses illuminance field distributions of LGPs with microstructures that were influenced by various μIM process parameters. The mold temperature was found to be the most important processing parameter affecting the illuminance field distribution of molded LGPs fabricated by μIM. The molded LGP with microstructures and the optimal design had better uniformity than that with microstructures and the primary design and that without microstructures. The uniformity of the LGP with microstructures and the optimal design was roughly 86.4%. Its uniformity was nearly 1.65 times that of the LGP without microstructures. The optimized design and fabrication of LGPs with microstructure exhibited good uniformity of illuminance field distributions.

Surface Wettability Tuning of Acrylic Resin Photoresist and Its Aging Performance.

Photoresist is the key material in the fabrication of micropatterns or microstructures. Tuning the surface wettability of photoresist film is a critical consideration in its application of microfluidics. In this work, the surface wettability tuning of acrylic resin photoresist by oxygen plasma or ultra-violet/ozone, and its aging performance in different atmospheres, were systematically studied. The chemical and physical characterizations of the surfaces before and after modification show a dramatic decrease in the C–C group and increase in surface roughness for oxygen plasma treatment, while a decrease of the C–C group was found for the UV/ozone treatment. The above difference in the surface tuning mechanism may explain the stronger hydrophilic modification effect of oxygen plasma. In addition, we found an obvious fading of the wettability tuning effect with an environment-related aging speed, which can also be featured by the decrease of the C–C group. This study demonstrates the dominated chemical and physical changes during surface wettability tuning and its aging process, and provides basis for surface tuning and the applications in microfluidics.

Control of Cell Geometry through Infrared Laser Assisted Micropatterning

The protocol presented here enables automated fabrication of micropatterns that standardizes cell shape to study cytoskeletal structures within mammalian cells. This user-friendly technique can be set up with commercially available imaging systems and does not require specialized equipment inaccessible to standard cell biology laboratories.

Rapid fabrication of hydrogel micropatterns by projection stereolithography for studying self-organized developmental patterning.

Self-organized patterning of mammalian embryonic stem cells on micropatterned surfaces has previously been established as an in vitro platform for early mammalian developmental studies, complimentary to in vivo studies. Traditional micropatterning methods, such as micro-contact printing (μCP), involve relatively complicated fabrication procedures, which restricts widespread adoption by biologists. Here, we demonstrate a rapid method of micropatterning by printing hydrogel micro-features onto a glass-bottomed culture vessel. The micro-features are printed using a projection stereolithography bioprinter yielding hydrogel structures that geometrically restrict the attachment of cells or proteins. Compared to traditional and physical photomasks, a digitally tunable virtual photomask is used in the projector to generate blue light patterns that enable rapid iteration with minimal cost and effort. We show that a protocol that makes use of this method together with LN521 coating, an extracellular matrix coating, creates a surface suitable for human embryonic stem cell (hESC) attachment and growth with minimal non-specific adhesion. We further demonstrate that self-patterning of hESCs following previously published gastrulation and ectodermal induction protocols achieves results comparable with those obtained with commercially available plates.