Polymer Replication Research Articles

Sub-Micron Replication of Fused Silica Glass and Amorphous Metals for Tool-Based Manufacturing.

The growing importance of submicrometer-structured surfaces across a variety of different fields has driven progress in light manipulation, color diversity, water-repellency, and functional enhancements. To enable mass production, processes like hot-embossing (HE), roll-to-rollreplication (R2R), and injection molding (IM) are essential due to their precision and material flexibility. However, these processes are tool-based manufacturing (TBM) techniques requiring metal molds, which are time-consuming and expensive to manufacture, as they mostly rely on galvanoforming using templates made via precision microlithography or two-photon-polymerization (2PP). In this work, a novel approach is demonstrated to replicate amorphous metals from fused silica glass, derived from additive manufacturing and structured using hot embossing and casting, enabling the fabrication of metal insets with features in the range of 300nm and a surface roughness of below 10nm. By partially crystallizing the amorphous metal, during the replication process, the insets gain a high hardness of up to 800 HV. The metal molds are successfully used in polymer injection molding using different polymers including polystyrene (PS) and polyethylene (PE) as well as glass nanocomposites. This work is of significant importance to the field as it provides a production method for the increasing demand for sub-micron-structured tooling in the area of polymer replication while substantially reducing their cost of production.

Manufacturing fused silica hemispherical resonators using polymer glass suspension and replication molding

This work introduces a new method for manufacturing fused silica (FS)-based hemispherical resonators (HSRs) using a printable polymer glass mixture and replication molding. This process involves 3D printing to create the mold, followed by the casting of a photo-reactive pre-polymer glass mixture. This technique allows us to produce complex 3D geometries and offers faster production of resonators compared to other traditional methods. In this study, we manufactured three devices and successfully identified resonance modes with two (N = 2), three (N = 3) and four (N = 4) nodes/antinodes in all three HSRs, demonstrating the repeatability of our new manufacturing method. The highest quality factor of 482 k was achieved for the N = 3 resonance mode using the ring-down method. Some of the key advantages of our method include producing multiple devices efficiently with relatively good surface quality, making it a viable option for producing high-precision devices in the future. Our new fabrication technique results in a device surface roughness of ∼100 nm (measured over an area of 250 μm × 250 μm) and manufacturing yield of over 90%. Moreover, all the steps involved in this method can be completed outside of a specialized cleanroom environment.

Generation of precision microstructures based on reconfigurable photoresponsive hydrogels for high-resolution polymer replication and microoptics

Microstructured molds are essential for fabricating various components ranging from precision optics and microstructured surfaces to microfluidics. However, conventional fabrication technology such as photolithography requires expensive equipment and a large number of processing steps. Here, we report a facile method to fabricate micromolds based on a reusable photoresponsive hydrogel: Uniform micropatterns are engraved into the hydrogel surface using photo masks under UV irradiation within a few minutes. Patterns are replicated using polydimethylsiloxane with minimum feature size of 40 μm and smoothness of Rq ~ 3.4 nm. After replication, the patterns can be fully erased by light thus allowing for reuse as a new mold without notable loss in performance. Utilizing greyscale lithography, patterns with different height levels can be produced within the same exposure step. We demonstrate the versatility of this method by fabricating diffractive optical elements devices and a microlens array and microfluidic device with 100 µm wide channels.

New design of bismuth borate ceramic/epoxy composites with excellent fracture toughness and radiation shielding capabilities

In the present work, ceramic/epoxy composites consisting of bismuth borate reticulated porous ceramics cross-linked with epoxy resin were prepared. The ceramic skeleton was prepared using the polymer replication method and exhibited a synergistic neutron/gamma shielding capability while also being able to disperse the phase. Additionally, the increased boric acid content in the slurry promotes the growth of pores on the surface of the ceramic skeleton and increases its roughness, which directly affects the bonding of the ceramic to the epoxy resin. The phase composition, microstructure, and physical properties of the ceramic skeleton, as well as the interfacial bonding, fracture mechanisms, and neutron/gamma shielding capabilities of the composites, are systematically described. The shielding rates of the prepared composites against neutrons and gamma rays were 67.3% and 16.82%, respectively. The bulk density and fracture toughness reached 2.22 g/cm3 and 54.64 MPa·m1/2, respectively. Our preparation process and analytical methods offer new opportunities for the effective design of flexible radiation shielding material for nuclear reactors.

Replicative manufacturing of metal moulds for low surface roughness polymer replication

Tool based manufacturing processes like injection moulding allow fast and high-quality mass-market production, but for optical polymer components the production of the necessary tools is time-consuming and expensive. In this paper a process to fabricate metal-inserts for tool based manufacturing with smooth surfaces via a casting and replication process from fused silica templates is presented. Bronze, brass and cobalt-chromium could be successfully replicated from shaped fused silica replications achieving a surface roughnesses of Rq 8 nm and microstructures in the range of 5 µm. Injection moulding was successfully performed, using a commercially available injection moulding system, with thousands of replicas generated from the same tool. In addition, three-dimensional bodies in metal could be realised with 3D-Printing of fused silica casting moulds. This work thus represents an approach to high-quality moulding tools via a scalable facile and cost-effective route surpassing the currently employed cost-, labour- and equipment-intensive machining techniques.

Innovative fabrication of diffractive surfaces on plastic parts via textures micromilled on NiP injection moulds

Diffractive microstructured surfaces are nowadays increasingly applied to polymeric parts for aesthetic, security and optical functionalities. However, both the machining of the mould blaze-grating and its replication on plastic are still representing challenging issues, from both the technical and economical points of view. In this work, an innovative process chain based on carbide tools micromilling of mould gratings was developed for mass production of diffractive patterns on injection moulded parts. A micromilling experimental campaign was conducted on a nickel-phosphorus (NiP) thick coating to machine a blaze-grating on the mould surface, evaluating the influence of the cutting parameters on the diffractive surface quality. Subsequently, the microstructures were replicated on ABS, PC and PMMA by injection moulding. The roughness parameters Sk, Spk and Svk were added with the idea that their sum is representative of the polymer replication of regular diffraction grating pattern. Moreover, the effect of the moulded grating surface quality on the optical performance was preliminarily assessed. The obtained results show that the proposed process chain is suitable for low-cost mass production of polymeric parts with diffractive microstructures.

Fabrication and Investigation of Bioceramic Scaffolds by a Polymer Sponge Replication Technique

Initially, hydroxyapatite powder was produced using the wet participation method. The x-ray diffraction and particle size analysis were performed after the preparation method of the powder. Using polymer replication technique to produce scaffolds of HAP with structural and physical properties appropriate to human trabecular bone. The microstructure and chemical bonding of the pours scaffolds were investigated by using XRD spectroscopy, scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) after the sintering at temperture1300 °C for 2 hours. The synthesized scaffold was soaked in medium of the simulated body fluid (SBF) in order to evaluate bioactivity. From the results, it was observed that the scaffolds were contained open and interconnected pores with porosity range between 72-75 %. In addition, SEM morphology analysis was indicated high bioactivity of pours scaffolds due to the creation of apatite layer on its surfaces were observed after soaking 7days in SBF media.

Thresholds in Origin of Life Scenarios.

SummaryThresholds are widespread in origin of life scenarios, from the emergence of chirality, to the appearance of vesicles, of autocatalysis, all the way up to Darwinian evolution. Here, we analyze the “error threshold,” which poses a condition for sustaining polymer replication, and generalize the threshold approach to other properties of prebiotic systems. Thresholds provide theoretical predictions, prescribe experimental tests, and integrate interdisciplinary knowledge. The coupling between systems and their environment determines how thresholds can be crossed, leading to different categories of prebiotic transitions. Articulating multiple thresholds reveals evolutionary properties in prebiotic scenarios. Overall, thresholds indicate how to assess, revise, and compare origin of life scenarios.

Functionalization of Plastic Parts by Replication of Variable Pitch Laser-Induced Periodic Surface Structures.

Surface functionalization of plastic parts has been studied and developed for several applications. However, demand for the development of reliable and profitable manufacturing strategies is still high. Here we develop and characterize a new process chain for the versatile and cost-effective production of sub-micron textured plastic parts using laser ablation. The study includes the generation of different sub-micron structures on the surface of a mold using femtosecond laser ablation and vario-thermal micro-injection molding. The manufactured parts and their surfaces are characterized in consideration of polymer replication and wetting behavior. The results of the static contact angle measurements show that replicated Laser-Induced Periodic Surface Structures (LIPSSs) always increase the hydrophobicity of plastic parts. A maximum contact angle increase of 20% was found by optimizing the manufacturing thermal boundary conditions. The wetting behavior is linked to the transition from a Wenzel to Cassie–Baxter state, and is crucial in optimizing the injection molding cycle time.

Reliable and Robust Fabrication Rules for Springtail-Inspired Superomniphobic Surfaces.

We report a reliable and robust method for the fabrication of bioinspired superomniphobic surfaces with precise concave-cap-shaped micropillar arrays. This method includes silicon-based conventional microelectromechanical systems (MEMS) and polymer replication processes. We have elucidated two critical cases of fabrication rules for precise micromachining of a negative-shaped bioinspired silicon master. The fabricated polymeric structure replicated from the semipermanent silicon master based on the design rules exhibited high structural fidelity and robustness. Finally, we validated the superomniphobic properties, structural durability, and long-term stability of the fabricated bioinspired surfaces.

X-ray LIGA Microfabricated Circuits for a Sub-THz Wave Folded Waveguide Traveling-Wave-Tube Amplifier

We report experimental results on the microfabrication of three types of folded waveguide circuits with a high aspect ratio by using a high-energy X-ray LIGA technique. A W-band folded waveguide with a total of 80 periods was designed for a traveling-wave-tube (TWT) amplifier operating at 90 GHz–100 GHz. The measured return loss and insertion loss of the W-band fabricated circuit were–10 dB and 0.42 dB/cm, respectively. A G-band circuit showed a higher insertion loss of 1.57 dB/cm. An additional circuit fabrication for a 850-GHz folded waveguide TWT was also successfully carried out. The broad-wall angle measured with respect to the narrow wall of the rectangular waveguide was very close to 90◦, indicating an excellent resolution compared to that of other microfabrication techniques, such as deep reactive ion etching (DRIE) and ultraviolet (UV) lithography, electroplating, and polymer replication (LIGA).

Fabrication of complex shaped ceramic articles from 3D printed polylactic acid templates by replication process

Abstract Porous honeycombs of three ceramic formulations and configurations were replicated from 3D printed polylactic acid (PLA) templates. Sacrificial PLA templates were coated with ceramic slurries of optimum rheology and were subjected to fugitive thermal degradation based on the TG-DTA patterns recorded followed by sintering. Though the polymer replication process is known, 3D printed PLA templates are not explored for fabrication of ceramic complex shapes. 3D printed PLA offers flexibility to produce complex ceramic parts with structural integrity and engineered porosity. In the present study, 3D printed template replication technique has been used to demonstrate fabrication of honeycombs with relative density as low as 0.1 with porosity of 75–85% which is alo complemented by microstructural studies. Further, the samples exhibited cellular behavior under quasistatic compression with high energy absorption capabilities and moderate compressive strength of 1.5–2.2 MPa depending upon the ceramic formulations.

Ultrasonic vibration technology for the polymer replication of high aspect ratio micro-structured surface

It is still a challenge to achieve the polymer replication of high aspect ratio micro-structured surface especially when the completed and unified replication quality is required. This paper shows a new method for the replication named ultrasonic vibration micro-injection mold (μUVIM) technology which combines the micro-injection mold (μIM) with ultrasonic vibration. An experimental mold that integrates micro-injection compression mold (μICM) and μUVIM has been designed. In this paper, the effect of important process parameters on the replication quality of microstructure was studied via μUVIM experiment, and the process parameters were optimized through the response surface method (RSM). Compared with replication methods based on μICM technology, the μUVIM technology discussed in this paper can increase the average height of the microstructure by 14.6% and increase the production efficiency by three times. Moreover, it has been found that the μUVIM technology is insensitive to the thickness of the polymer substrate, so it can widen the processing scope of microstructure with high aspect ratio.

A compact and high-power silicon-wafer solar strip-cells-array module integrated with an array concentrator**Project supported by the National Natural Science Foundation of China (Grant Nos. 61377021 and 61671329).

A compact, low-cost and high-output-power silicon-wafer solar strip-cells-array module (SCAM) was experimentally demonstrated. The proposed SCAM consisted mainly of a silicon-wafer strip-cell sparse array and low-concentration-ratio array concentrator based on an epoxy resin polymer (ERP) cylindrical plano-convex lens. A polymer replication process based on a polydimethylsiloxane mold was used to fabricate the ERP lens array concentrator. The results show that 46.94% of the silicon-wafer cell was saved in the designed SCAM. Moreover, the output power of the SCAM with a low concentration ratio of 8 suns was improved by 8.6%, compared with a whole piece of a conventional silicon-wafer solar cell with the same area as the module. The proposed method encapsulating solar cells provides a means to reduce the usage of silicon cells in modules as well as improving the output power of modules.

RETRACTED: A Si-αTCP Scaffold for Biomedical Applications: An Experimental Study Using the Rabbit Tibia Model

We herein hypothesize that bioceramics with an appropriate architecture made of Si-αtricalcium phosphate (Si-αTCP) meet the biocompatibility and biological safety requirements for bone grafting applications. Polyurethane sponges were used as templates, soaked with ceramic slurry at different ratios and sintered at 1400 °C for 3 h at heating and cooling rates of 5 °C/min. Four critical size defects of 6 mm Ø were created in 15 NZ tibias. Three working times were established as 15, 30 and 60 days. A highly porous Si-αTCP scaffold with micro and macropores and pore interconnectivity was produced by the polymer replication method. Considerably more bone formation took place in the pores and the periphery of the implant for the Si-αTCP scaffolds than for the control group. The ceramic scaffold (68.32% ± 1.21) generated higher bone-to-implant contact (BIC) percentage values (higher quality, closer contact) than the control group, according to the histomorphometric analysis, and defect closure was significant compared with the control group. The highest percentages of BIC and bone formation were found after 60 days of implantation. These results suggest that the Si-αTCP scaffold is advantageous for initial bone regeneration.

Fused Deposition Modeling 3D Printing for (Bio)analytical Device Fabrication: Procedures, Materials, and Applications.

In this work, the use of fused deposition modeling (FDM) in a (bio)analytical/lab-on-a-chip research laboratory is described. First, the specifications of this 3D printing method that are important for the fabrication of (micro)devices were characterized for a benchtop FDM 3D printer. These include resolution, surface roughness, leakage, transparency, material deformation, and the possibilities for integration of other materials. Next, the autofluorescence, solvent compatibility, and biocompatibility of 12 representative FDM materials were tested and evaluated. Finally, we demonstrate the feasibility of FDM in a number of important applications. In particular, we consider the fabrication of fluidic channels, masters for polymer replication, and tools for the production of paper microfluidic devices. This work thus provides a guideline for (i) the use of FDM technology by addressing its possibilities and current limitations, (ii) material selection for FDM, based on solvent compatibility and biocompatibility, and (iii) application of FDM technology to (bio)analytical research by demonstrating a broad range of illustrative examples.

Effect of strontium substitution on the cytocompatibility and 3-D scaffold structure for the xSrO-(10-x) MgO-60SiO2-20CaO-10 P2O5 (2 ≤ x ≤ 8) sol-gel glasses.

In the present study, novel glasses xSrO-(10-x) MgO-60SiO2-20CaO-10 P2O5 (2 ≤ x ≤ 8, in steps of 2) are synthesized via sol-gel method. The current work focusses on the evaluation of mechanical, physical and biocompatible properties for sol-gel glasses. The pore size and surface area of these glasses were studied using BET analysis. The structural aspect of the glasses/glass ceramics was studied by XRD and Raman spectroscopy. The cytotoxicity assays were conducted for MG63 human osteosarcoma cell line. Furthermore, the as prepared glasses were used for the fabrication of 3-D porous scaffolds via polymer replication method. The loaded green bodies have been sintered at 700, 800 and 900 °C and were kept for 6 h to densify the glass network. The effect of sintering temperature on the structure and properties of as prepared scaffolds were analyzed via scanning electron microscopy (SEM) and porosity calculations.

New 3D stratified Si-Ca-P porous scaffolds obtained by sol-gel and polymer replica method: Microstructural, mineralogical and chemical characterization

The aim of this research was to develop and characterize a novel stratified porous scaffold for future uses in bone tissue engineering. In this study, a calcium silicophosphate porous scaffold, with nominal composition 29.32wt% SiO2 – 67.8wt% CaO – 2.88wt%P2O5, was produced using the sol-gel and polymer replication methods. Polyurethane sponges were used as templates which were impregnated with a homogeneous sol solution and sintered at 950°C and 1400°C during 8h. The characteristics of the 3D stratified porous scaffolds were investigated by Scanning Electron Microscopy, X-Ray Diffraction, Fourier Transform Infrared Spectrometry, Diametric Compression of Discs Test and Hg porosimetry techniques. The result showed highly porous stratified calcium silicophosphate scaffolds with micro and macropores interconnected. Also, the material has a diametrical strength dependent on the number of layers of the stratified scaffolds and the sintering temperature.

Non-Lithographic Silicon Micromachining Using Inkjet and Chemical Etching.

We introduce a non-lithographical and vacuum-free method to pattern silicon. The method combines inkjet printing and metal assisted chemical etching (MaCE); we call this method “INKMAC”. A commercial silver ink is printed on top of a silicon surface to create the catalytic patterns for MaCE. The MaCE process leaves behind a set of silicon nanowires in the shape of the inkjet printed micrometer scale pattern. We further show how a potassium hydroxide (KOH) wet etching process can be used to rapidly etch away the nanowires, producing fully opened cavities and channels in the shape of the original printed pattern. We show how the printed lines (width 50–100 µm) can be etched into functional silicon microfluidic channels with different depths (10–40 µm) with aspect ratios close to one. We also used individual droplets (minimum diameter 30 µm) to produce cavities with a depth of 60 µm and an aspect ratio of two. Further, we discuss using the structured silicon substrate as a template for polymer replication to produce superhydrophobic surfaces.

Novel Resorbable and Osteoconductive Calcium Silicophosphate Scaffold Induced Bone Formation.

This aim of this research was to develop a novel ceramic scaffold to evaluate the response of bone after ceramic implantation in New Zealand (NZ) rabbits. Ceramics were prepared by the polymer replication method and inserted into NZ rabbits. Macroporous scaffolds with interconnected round-shaped pores (0.5–1.5 mm = were prepared). The scaffold acted as a physical support where cells with osteoblastic capability were found to migrate, develop processes, and newly immature and mature bone tissue colonized on the surface (initially) and in the material’s interior. The new ceramic induced about 62.18% ± 2.28% of new bone and almost complete degradation after six healing months. An elemental analysis showed that the gradual diffusion of Ca and Si ions from scaffolds into newly formed bone formed part of the biomaterial’s resorption process. Histological and radiological studies demonstrated that this porous ceramic scaffold showed biocompatibility and excellent osteointegration and osteoinductive capacity, with no interposition of fibrous tissue between the implanted material and the hematopoietic bone marrow interphase, nor any immune response after six months of implantation. No histological changes were observed in the various organs studied (para-aortic lymph nodes, liver, kidney and lung) as a result of degradation products being released.