Nickel Stamp Research Articles

지르코니아 나노입자 기반 나노패턴 금속 몰드 제작과 열가소성 재료의 복제성형 응용

Fabrication of a durable and strong nanopatterned mold insert using metal sheet and plate is important for molding of thermoplastic materials. Conventionally, the nickel stamper replicating a master pattern by electroforming process has been used for injection molding of nanotextured products such as Blu-ray media. However, a more facile and cheaper mold fabrication process is highly required for manufacturing of functional products based on nanostructured surface. In this study, zirconia nanoparticles were blended with UV curing polymer to fabricate a polymer nanocompositebased nanopattern mold. Compared to the cured pure Ormostamp, the modulus of elasticity of the nanocomposite filled with approximately 54 vol% of zirconia nanoparticles increased by 160 times. Additionally, the modulus of elasticity reached 197 ㎬ by thermal decomposition of the UV-Cured polymer and post-annealing at 800°C of the nanoparticle layer. The nanopatterns were formed on stainless steel sheet and block, and applied to hot embossing of the PMMA films and injection molding of the COC materials, respectively. No deterioration of the mold occurred during the hot embossing 30 times and the injection molding 600 shots. Nanoparticle-enhanced UV curing nanocomposites or post-heat treatment methods are cost-efficient and easy, because many molds can be manufactured from one master pattern.

Fabrication of curved diffractive optical elements by means of laser direct writing, electroplating, and injection compression molding

In this work, a new process chain for the fabrication of curved micro-structured optical elements by injection compression molding is investigated. The fabrication is demonstrated for the example of a curved diffractive optical element (DOE). In a first process step a master substrate is fabricated using laser direct writing on a curved glass substrate. Blazed diffractive micro-structures with lateral feature sizes down to 5 μm and height of 1.6 μm are created. A subsequent electroplating process is applied to create a nickel stamper to be used as a tool insert for the molding process. During electroplating, a 3 mm nickel layer is formed, transferring the diffractive structures from the master substrate into a solid mold insert. The nickel stamper shows an accurate reproduction of the micro-structures. The mold insert is integrated into an injection compression molding tool to replicate the optical elements. Results show that the blazed diffractive structures are replicated with a high quality. Tests of the components within a chromatic-confocal measurement setup confirm that they can potentially replace expensive conventional elements.

Nickel stamp origination from generic SU-8 nanostructure arrays patterned with improved thermal development and reshaping

In this study, we show that rapid, reliable, and scalable custom-input colour patterning and eye-readable data storage can be achieved through high-throughput nanoimprinting-exposure-thermal-treatment (NETT) and thermal development and reshaping (TDR) techniques. The main impediment for commercial realization of high-resolution metasurfaces using NETT and TDR is the cost and speed of stamp origination as well as the quality and durability of the fabricated stamp. In order to accelerate the patterning process, lower the fabrication costs, and obtain patterns with high-resolution, we introduce and optimize a new method for origination of durable Ni stamps by electroplating on an SU-8 master fabricated according to custom-input colour patterns via NETT and TDR. In these processes, laser exposure is used to locally activate the generic RGB pixels fabricated on SU-8 via thermal nanoimprint lithography (NIL), according to the custom design. Upon TDR treatment, the exposed regions crosslink while the unexposed areas flatten. TDR is optimized to find the fastest processing condition that results in minimum nanocone height reduction and maximum diffraction efficiency. AFM results show that the TDR-processed nanocones in all red, green, and blue subpixels witness minimal shrinkage in comparison with the corresponding as-imprinted RGB pixels. Among three different sets of direct baking and ramping temperature TDR experiments, direct 55 °C-10 min TDR is found to be the optimal recipe. As a proof-of-concept, the originated stamp was employed to replicate colour images on PET and glass substrates using UV-thermal NIL. The reproduced colour image, photographed at pre-defined lighting and viewing angles, bears vivid diffractive colours with different RGB ratios that are in good match with the custom-input image. Furthermore, the red, green, and blue diffraction peaks from the TDR-55 °C-baked sample exhibit either trivial or no distinguishable difference as compared to the corresponding peaks in the as-imprinted sample.

Usage of Janus green B for the improvement of the filling effect during replication process of nanoimprint nickel stamp

This work proposes a simple replication process of nanoimprint nickel stamp with the usage of Janus Green B (JGB) for the improvement of the filling effect to eliminate the voids forming in high aspect ratio nanotrenches during nanoelectroforming process. As JGB molecules tend to adsorb at the edge of the nanotrench with high electron density, the metal deposition rate is reduced at the edge of the nanotrench. Therefore, the voids are not formed due to the elimination of the sealing phenomenon during electrodeposition process. On the basis of the proposed process, a nickel nanoimprint stamp with six nanograting areas of 1.3 mm × 1.3 mm size, 200 nm pitch, 80 nm linewidth and 200 nm depth was replicated successfully. The experiment results demonstrate that the filling effect is gradually improved with the addition of JGB in the replication process of the nickel stamp.

Fabrication of nickel stamp using e-beam evaporation and electroforming for electroreduction of carbon dioxide

Electronic properties and electroanalytical behaviors are highly dependent on the morphologies of electrodes. Thus, many techniques are continuously developed to enhance carrier mobility by promoting the ordered packing of electrodes. In this work, the authors investigated the electroanalytical behavior of different prepared electrodes by controlling the morphologies of the electrodes through semiconductor-manufacturing techniques. A nickel stamp was fabricated by using photolithography, inductively coupled plasma etching, e-beam evaporation, and the electroforming technique. The stamp was used as an electrochemical electrode in a standard three-electrode cell in aqueous solution, thereby revealing the relationships among the microstructure, nickel stamp, and zinc oxide as a function of applied potential. The electrochemical reduction reaction was carried out in a conventional reactor in the presence of carbon dioxide. This reaction exhibited a higher faradaic efficiency for carbon monoxide and methane than that observed when flat nickel electrodes were used.

Hierarchical micro/nano-structured nanoimprinting stamp fabrication for superhydrophobic application

ABSTRACTThe hierarchical micro/nano structure of a real lotus leaf was successfully transferred to a nickel stamp, and it was used as a nanoimprinting stamp for superhydrophobic surface preparation. The hierarchical micro-bump/nano-tubule structure of the lotus leaf was transformed to a nano-wrinkled micro-bump in order to apply the nanoimprinting process and provide superhydrophobicity. Ag nanoparticles (AgNPs) were uniformly coated over the lotus leaf surface to form an electrically conducting seed layer, followed by a nickel electroplating process. A nickel stamp with a well-defined negative structure of a lotus leaf, including even nano-wrinkled microstructure, was thereby successfully fabricated. The micro/nano pattern of the lotus leaf was successfully reduplicated on a poly vinyl chloride (PVC) film by a nanoimprinting process using the nickel stamp. According to contact angle measurements, the nanoimprinted polymer films are rendered hydrophobic. Superhydrophobicity was then obtained by applying a self-assembled monolayers (SAM) coating over the nanoimprinted polymer film.

Low-cost replication of self-organized sub-micron structures into polymer films

In this paper, the results of exploiting self-organized sub-micron polystyrene (PS) wrinkle patterns possessing random orientation, in preparation of a nickel stamp for hot embossing purposes, are presented. Self-organized patterns were prepared employing a method in which a stiff cross-linked capping layer on the topmost part of the soft polystyrene layer was created by using reactive ion etching (RIE) device with mild conditions and argon as a process gas, and the wrin- kle formation was initiated thermally. Different surface patternings were obtained using silicon and stainless steel (SST) wafers as substrates. Prepared Ni-stamps were employed in hot embossing of polycarbonate (PC) and cyclo-olefin polymer (COP) films, using a nano-imprinting process. The replication quality of the self-organized wrinkle structures in PC and COP films was monitored by comparing the shape and dimensions of the original and final surface structures. The hot embossed sub-micron scale features, originally formed on stainless steel substrate, were found to have influence on the optical properties of the PC and COP films by lowering their reflectances.

Fabrication of concave microlens array diffuser films with a soft transparent mold of UV-curable polymer

A new lithographic approach for the fabrication of an enticing optical diffuser with concave microlens array (MLA) is reported. A flexible photopolymerizable polymer mold is employed as an intermediate transferring template from nickel stamp and directly adopted to fabricate concave MLA diffuser films. The influence of the parameters (such as diameter, fill factor etc.) of concave MLA is analyzed experimentally and theoretically. The results verify that the optical gain can be reached as high as 53%, which has a similar fascinating diffusion effect compared with that of conventional convex MLA diffuser films. Additionally, it is found that diffusion angle could be manipulated by the profile of the concave elliptical MLA, leading to luminance increase in long axis larger than that in short axis. The approach demonstrated here affords the intriguing opportunity to large scale industrial processing for high-quality diffusers with low manufacturing and materials cost.

Replication of rose petal surfaces using a nickel electroforming process and UV nanoimprint lithography

In this research, we replicate the hierarchical structures of rose petals by using poly urethane acrylate (PUA) nanomolding technology. After a molding process, we use a PUA replica as the mother mold for nickel electroforming processes. By replicating the original rose petal hierarchical structure, we obtain the rose petal effect with nickel substrates. In order to make a negative-patterned nickel stamp, a second PUA replication was done using the first PUA mother mold and a nickel electroforming process was performed. Using these, the hierarchical structure of rose petals was imprinted in perfluoropolyether (PFPE), which exhibited the petal effect.

Novel Embossing System for Replicating Micro-Structures on Curved Surfaces

Abstract Hot embossing is widely used to replicate micro-structures on polymer plate surfaces. The polymer parts of curved surfaces with micro-structures have important functions in various optoelectronic components. However, due to the high precision needed for embossing machines and mold manufacturing, achieving uniform pressure on curved surfaces during the embossing process is difficult. This study modified conventional hot embossing processes to develop an elastic bag embossing system (EBES) for replicating micro-structures on curved surfaces. The pressure equalizing properties of the elastic bag enabled uniform application of pressure on curved surfaces embossed with a general hot compression machine. For the EBES-assisted hot embossing process, a nickel stamper was attached to the elastic bag to compress and replicate micro-structures on the PC film covering the mold surface with single direction curve. This study also developed an EBES-assisted UV exposure process that used a PDMS soft-mold attached to the elastic bag surface to compress the UV curable photoresist covering the surface of the convex lens. Micro-structures were then formed by exposing the photoresist. Experimental results showed that the EBES with Ni stamper could successfully replicated micro-structures onto a 200 mm × 200 mm curved PC film and that the EBES-assisted UV exposure could successfully produced a 50 mm diameter fresnel lens on a convex profile with material of UV photoresist. Experimental tests of pressure-sensitive film showed that EBES enables uniform application of pressure on curved surfaces during the embossing process on standard hot compression machines. The experimental results confirm that the EBES developed in this study is an efficient and economical method for replicating micro-structures on curved surface.

Microfluidic chip designs process optimization and dimensional quality control

The challenge of fabricating geometries with critical dimensions ranging from few microns down to 10 nm with high production rate is delaying the development of nanotechnology based products. Diverse research works have shown the capability of technologies such as UV lithography, nano imprint lithography and e-beam lithography to produce micro and nano features. However, their application for tooling purposes is relatively new and the potential to produce nanometer features with high volume and low cost is enormous. Considering possible implementation in a mass production environment the precision of measuring results and the accuracy of measurement relocation are very relevant. In this paper, the capability of producing with high volume Lab-on-chip devices through injection molding is evaluated. Preparation of master geometries was made in a Si wafer using e-beam lithography and reactive ion etching. Subsequent nickel electroplating was employed to replicate the obtained geometries on the tool, which was used to mold on transparent polymer substrates the functional structures. To assess the critical factors affecting the replication quality throughout the different steps of the proposed process chain, test geometries were designed and produced on the side of the functional features. The so-called "Finger Print" of the lithography and molding processes was qualitatively and quantitatively evaluated through scanning electron microscopy and atomic force microscopy respectively. The entire process chain is therefore characterized and the degree of replication among the different replication steps quantified with precise measurements using a high accuracy relocation technique on the produced key test geometries. Influence of injection molding process parameters, feature dimensions and orientation relative to the polymer flow direction have been assessed in respect of the replication fidelity of the produced micro/sub-μm channels. Finally the paper addresses product compliance with specifications, focusing on tolerances of vertical dimensions using a metrological approach: sub-μm features on silicon, nickel stampers and injection molded substrates are measured. Results of measurement uncertainty calculation, quantitative replication fidelity assessment, and dimensional tolerances at the nanometer scale verification are reported.

Effects of adding injection–compression to rapid heat cycle molding on the structure of a light guide plate

This study investigates the effects of adding injection–compression to rapid heat cycle molding (RHCM) (rapid heat cycle injection–compression molding (RICM)) on the physical quality and optical anisotropy of a molded light guide plate (LGP). Transcription ratio of microstructure, uniformity of part thickness and birefringence were experimentally evaluated on a 7 inch LGP of nominal thickness of 1.12 mm (including a microstructure array of 30 µm diameter and 14 µm height). The designed mold was equipped with rapid heating and compressing facilities and a microstructured nickel stamper was fabricated by UV LIGA process. In addition, to investigate the efficacy of RICM, experiments involving conventional injection molding (CIM), ICM, and RHCM were conducted in parallel with RICM using the same mold. RHCM and RICM yielded excellent transcription ratios for the microstructure, while CIM and RICM provided high thickness uniformity and low birefringence. Thus, RICM obtains high transcription ratio of microstructure, uniform thickness and low birefringence.

Design and Fabrication of Bilayer Wire Grid Polarizer Using Ultraviolet Replicated Nanograting against Nickel Electroformed Nanostamp

A bilayer wire grid polarizer (B-WGP) composed of UV-replicated nanograting and deposited aluminum layer was designed, fabricated, and evaluated as a simpler and less costly reflective polarizer. To design the B-WGP structure, a parametric study of structural design factors on the simulated performance was conducted using rigorous coupled wave analysis. A durable electroformed nickel stamp was fabricated using a lithographed photo resist master pattern having a nanograting with a pitch of 110 nm, a line width of 65 nm, and a height of 80 nm. A polymer grating was fabricated by the UV replication process, and an aluminum layer with a thickness of 50 nm was deposited by electron-beam evaporation. To examine the performance of the fabricated bilayer wire-grid polarizer, the transmission spectra of p- and s-polarized light, and the extinction ratio spectra were measured and compared with the simulated values. The measured transmittance of p-polarized light and the extinction ratio of the fabricated bilayer wire grid polarizer were ∼40% and ∼103 in whole visible ranges, respectively.

급성 심근경색 검지를 위한 비표지식 단백질 센서 제작 및 검증에 관한 연구

We proposed a method to fabricate label-free protein sensor with sub-wavelength nanograting structures to be used for diagnosing acute myocardial infarction. A nickel stamp for the injection molding of nanograting integrated protein sensor was fabricated by electroforming process with high fidelity. By using metallic stamp, we replicated label-free protein sensor via injection molding, which is an outstanding method for low-cost and mass production of polymer products. Finally, we performed a feasibility test, examining cardiac troponin T (cTnT) and anti-cTnT interactions. From the results, we demonstrated that the fabricated protein sensor can provide information for the early and accurate detection of cardiac diseases such as acute myocardial infarction.

Simple process for 60 nm patterned nickel stamp replication

A simple process for nickel nanoimprint stamp replication is proposed. Based on this process, the replication of a 15 × 20 mm nickel nanoimprint stamp with 60 nm grating structures was carried out. First, the nanograting structures on the master silicon stamp were transferred to a polymer substrate using the hot embossing process; then, a layer of nickel was sputtered to fill the nanostructures on the substrate surface and form the seed layer for the electroforming process; finally, the back plane of the replica is electroformed. The observation results show good correlation between the dimensions of the master stamp's features and the corresponding replicated features. The performance test result of the replicated stamp demonstrated that the mechanical strength of the replica is sufficient for the hot embossing process.

광소자의 광 정렬 및 연결 구조 구현용 임프린트 공정 연구

Optical devices are used extensively in the field of information network. Increasing demand for optical device, optical interconnection has been a important issue for commercialization. However many problems exist in the interconnection between optical device and optical fiber, and in the case of the multi-channel, problems of the optical alignment and optical array arise. For solving the alignment and array problem of optical device and the optical fiber, we fabricated fiber alignment and array by using imprint technology. Achieved higher precision of optical fiber alignment and array due to fabricating using imprint technology. The silicon stamp with different depth was fabricated using the conventional photolithography. Using the silicon stamp, a nickel stamp was fabricated by electroforming process. We conducted imprint process using the nickel stamp with different depth. The optical alignment and array by fabricating the patterns of optical device and fiber alignment and array using imprint process, and achieved higher precision of decreasing the dimensional error of the patterns by optimization of process. The fabricated optical interconnection of PLC device was measured 3.9 dB and 4.2 dB, lower than criteria specified by international standard.

Design and fabrication of a metallic nanostamp using UV nanoimprinting and electroforming for replicating discrete track media with feature size of 35 nm

The demand for high-density data-storage media is increasing, necessitating the development of novel magnetic data-storage technologies. Among the various types of storage media, discrete track media (DTM) is an emerging technology that is being used to overcome the limitations of conventional continuous magnetic data-storage technology, such as the superparamagnetic effect and medium noise. In this study, the authors propose a method of fabricating a metallic stamp for replicating DTM patterns using ultraviolet (UV) nanoimprinting and electroforming, which are inexpensive processes that can be used to fabricate nanostructures with high precision. First, a silicon nanomaster with a feature size of 35 nm and a pitch of 70 nm was designed and fabricated by electron-beam recording and inductively coupled plasma etching. The measured pitch of the silicon master was 71.6 nm. Then, a polymeric master with a full track of nanoline patterns was then replicated from the silicon nanomaster via UV nanoimprinting. To improve the releasing properties during UV nanoimprinting, the silicon nanomaster was coated with a self-assembled monolayer of fluoroctatrichlorosilane. The measured average pitch and height of the replicated polymer master were 71.5 and 61 nm, respectively. Then, a metallic nanostamp with a thickness of 300 μm and a diameter of 80 mm was fabricated using electroforming. The metallic nanostamp was successfully fabricated, and its geometrical properties were measured and analyzed. The pitch and height of fabricated nickel stamp were 71.2 and 60.3 nm, respectively.

Wrinkle Formation and Imprinting of Gold Film Deposited on Polydimethylsiloxane

Bi-axial tensile stress was applied on a polydimethylsiloxane film and mounted on a PMMA plate surface. Then, the film’s tensile strain was fixed and the gold film was sputtered onto the surface. A wrinkle pattern was found during the release of tensile strain because of the friction effect between the PMMA plate and a polydimethylsiloxane film. A nickel stamp with a wrinkle structure fabricated using electroforming process and the polymeric wrinkle structure can be replicated successfully by electroforming and by imprinting process.

Nanofabrication of Nickel Stamp for Replication of Polymer Multilevel Nanolens Arrays via Modified Two-Step Anodization Process

In the present study, we propose a novel and low-cost nanofabrication technique for a nickel stamp for mass replication of polymer multilevel nanolens (MLNL) arrays. The present nanofabrication technique consists of a modified two-step anodization process and successive electroforming processes. As the first step in the fabrication of the nickel stamp, an aluminum template with multilevel nanodimple (MLND) arrays on an aluminum substrate was precisely fabricated by a modified two-step anodization, in which the processing condition of the second anodization step was changed. A nickel stamp with MLND arrays for the replication of a polymer substrate with MLNL arrays was achieved by electroforming onto the aluminum template with MLND arrays (a nickel template with MLNL arrays) followed by a second electroforming onto the obtained nickel template with MLNL arrays. The fabricated nickel stamp with MLND arrays was successfully used to replicate the polymer substrates with MLNL arrays via a hot embossing process.

Fabrication of Polymer Micropyramid/Nanolens Combined Structures Using Microstructured Nanodimpled Aluminum Stamp

In this study, we present an efficient and low-cost fabrication technique of polymer micropyramid/nanolens combined structures (MPNL-CS). The present fabrication technique is based on hot embossing of polymer substrates using a microstructured nanodimpled aluminum (MNA) stamp. The MNA stamp for the replication of polymer MPNL-CS was realized by combining three fabrication steps. (1) A nickel stamp with micropyramid array was manufactured by electroforming onto an anisotropically wet-etched silicon substrate. (2) A reverse micropyramid cavity array was transcribed on an electropolished aluminum substrate by microindentation with the nickel stamp. (3) The MNA stamp was finally realized by forming nanodimple arrays onto the reverse micropyramid array on the aluminum substrate through an electrochemical oxidation (anodization) process. In the final step, we have optimized the electrochemical oxidation process to realize nanodimple arrays at the sharp edge reverse micropyramid without defects. The MPNL-CS were successfully replicated on polymer substrates via a hot embossing process with the fabricated MNA stamp through investigating the effect of embossing pressure on the transcription quality of MPNL-CS. The present fabrication technique can be widely applied to the realization of various types of three-dimensional micro/nano combined structures.