Mold Fabrication Process 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.

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.

Gradient wettability induced by deterministically patterned nanostructures

We report a large-scale surface with continuously varying wettability induced by ordered gradient nanostructures. The gradient pattern is generated from nonuniform interference lithography by utilizing the Gaussian-shaped intensity distribution of two coherent laser beams. We also develop a facile fabrication method to directly transfer a photoresist pattern into an ultraviolet (UV)-cured high-strength replication molding material, which eliminates the need for high-cost reactive ion etching and e-beam evaporation during the mold fabrication process. This facile mold is then used for the reproducible production of surfaces with gradient wettability using thermal-nanoimprint lithography (NIL). In addition, the wetting behavior of water droplets on the surface with the gradient nanostructures and therefore gradient wettability is investigated. A hybrid wetting model is proposed and theoretically captures the contact angle measurement results, shedding light on the wetting behavior of a liquid on structures patterned at the nanoscale.

Advances in the Processing of UHMWPE-TiO2 to Manufacture Medical Prostheses via SPIF.

This research focuses on developing a novel ultra high molecular weight polyethylene (UHMWPE) material reinforced with titanium dioxide (TiO) nanoparticles for producing craniofacial prostheses via an incremental sheet forming process (SPIF). First, UHMWPE-TiO nanocomposite sheets were produced using incipient wetting and the compression molding process by considering different concentrations of TiO nanoparticles. Then, the influence that the compression molding fabrication process has on the crystallinity and structural properties of the produced sample sheets was investigated. Experimental characterizations via scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), tensile mechanical testing, and live/dead cell viability assays provided data that show an enhancement of the physical, mechanical, and biological properties. Finally, modifications on the nanocomposite material properties due to the SPIF manufacturing processes of a craniofacial prosthesis are addressed.

Simulation-Based Optimization of Plastic Injection Molding Parameter for Aircraft Part Fabrication Using Response Surface Methodology (RSM)

The small size and thin part characteristics of the honeycomb floor panel for the aircraft part product may cause problems in injection molding fabrication process. The objectives of this study is to find the most appropriate parameter in injection molding process for honeycomb floor panel by simulation using MoldFlow software and optimize the quality of injection molding process parameter by using Response Surface Methodology (RSM) as to obtain an optimal response and meets the requirement specification in the aviation scope. The crucial responses are shrinkage and warpage. Melt temperature, filling pressure and injection time are selected as the most influential factor for shrinkage and warpage. Model response was fitted by quadratic model. As the results, the optimum value suggested by the software were melt temperature of 360.02c, 60 MPa filling pressure and 4.70s injection time. With small differences error value between solution and simulation, 0.3% for shrinkage and 0.6% for warpage, the results was acceptable.

마이크로 핫엠보싱 최신 연구 동향

Micro hot-embossing is a powerful tool in the agile additive manufacturing industry. Its applications include optical components, micro-fluidic devices, MEMS, hydrophobic/hydrophilic surfaces, and energy harvesting devices. To overcome a drawback of low-process speed, the R2R process has been innovated, with novel embossing mechanisms and process optimization. Also, new materials beyond thermoplastic polymers have been applied to develop new devices, or enhance device performance. This review surveys recent progress in micro hot-embossing technology, in terms of new mold fabrication process, process innovation, and various applications.

Investigation on thermal properties of Styrene Acrylonitrile (SAN) matrix with Polytetrafluroethylene (PTFE) particle reinforced composites

Temperature utilization of composites materials depends on its thermal conductivity and co-efficient of thermal expansion. Polymers are exceptionally combustible because of their structure and they can’t fulfill a few applications. Thermal treatment of soften polymer because of the preparing setup by injection molding fabrication process able to control polymer structure (fitting) and in this manner deciding its thermal conduct. The fundamental point of this work is to contemplate the impact of Polytetrafluroethylene polymer (PTFE) as particle with Styrene Acrylonitrile polymer (SAN) as matrix to examine its thermal properties. Samples of 100% SAN and 10% PTFE by weight, 20% PTFE by weight blended specimens with SAN are prepared successfully by Injection molding process. Heat capacity, Thermal expansion, Thermal conductivity and Thermal degradation are the thermal properties examined. From the observations it was found that PTFE particles blended samples exhibits maximum thermal conductivity and good dimensional stability.

Rapid fabrication method of a microneedle mold with controllable needle height and width.

The main issue of transdermal drug delivery is that macromolecular drugs cannot diffuse through the stratum corneum of skin. Many studies have pursued micro-sized needles encapsulated with drugs to overcome this problem, as these needles can pierce the stratum corneum and allow drugs to enter the circulatory system of the human body. However, most microneedle fabrication processes are time-consuming and require expensive equipment. In this study, we demonstrate a rapid method for fabricating a microneedle mold using drawing lithography and a UV-cured resin. The mold was filled with a water-soluble material, polyvinylpyrrolidone (PVP), which was then demolded to produce a water-soluble microneedle array. The results of an in vitro skin insertion test using PVP microneedles and pig ear skin demonstrated the feasibility of the microneedle mold. In addition, by controlling the viscosity of the UV-cured resin through various heat treatments, microneedles with different heights and aspect ratios were produced. Compared with other methods, this technology significantly simplifies and accelerates the mold fabrication process. In addition, the required equipment is relatively simple and inexpensive. Through this technology, we can rapidly fabricate microneedle molds with controllable dimensions for various applications.

A NEW CERAMIC CASTING MOLD MADE BY GEL CASTING USING SILICA SOL AS A BINDER

This Paper presents a new ceramic casting mold made by gel casting using silica sol as a binder. The new ceramic mold is consisted of an alumina-mullite-zirconia matrix with the ratios of 38.332 wt. % alumina, 34.378 wt. % mullite, and 27.294 wt. % zirconia respectively, the slurry is mixed then the gelling agent is added and poured into the pattern. After gelation the mold is extracted and left to dry, then sintered. There are three main defects appear in the mold fabrication process. The 1st defect is the mold cracking, as a result of forced shrinkage of mold into pattern. The 2nd defect is the bad gelation behavior of mold, as a result of non equal gelling time. The last defect is mold surface cracks, due to increased silica ratio added to the mixture. As zirconia increased the bulk density and apparent porosity is increased, leading to higher mold permeability which is important to eliminate trapping of residual gases. The increased zirconia content decreases the micro hardness and the cold crushing strength, but increases the thermal shock resistance due to phase transformation during sintering. The ceramic mold is applicable for nodular cast iron so that the mold is hard enough to withstand the forces of spheroidal graphite formation when nodular cast iron is poured into the ceramic mold. The surface roughness no. of metal cast into ceramic mold is 0.582 μm, while of the metal cast into sand mold is 5.187 μm.

(Invited) Fabrication of Micro- and Nanostructures for High Efficiency Energy Conversion By Using Anodic Porous Alumina

The fabrication of micro - and nanostructured materials with controlled geometrical structures has attracted increasing interest for the preparation of various types of energy conversion devices with high efficiencies. The use of the material, which has naturally occurring ordered structures, is effective for the fabrication of the micro- and nanostructures of various kinds of materials. Anodic porous alumina, which is formed by anodization of Al in acidic solution, is a promising candidate for the fabrication of micro- and nanostructured materials with controlled geometrical structures1,2. One of commonly used process for the fabrication of micro- and nanostructures using anodic porous alumina is a template synthesis3,4. This process can generate the micro- and nanostructures with controlled geometrical structures, which are useful for the fabrication of high efficient energy conversion devices. However, the problem of the usual template synthesis is the low throughput due to the difficulty of the repeated use of the template. To solve this problem, we have been studying the new types of processes, which allow the high throughput formation of micro- and nanostructures. In the present report, recent results concerning the high throughput fabrication process for the micro- and nanostructures of metals and metal oxides, which can be applied to the energy conversion devices. The processes include the molding fabrication process for metal nanowires, and the membrane emulsification for uniform sized nanoparticles of metal oxides5,6 by using anodic porous alumina. These processes allow the high throughput fabrication of micro- and nanostructures because the starting structures of anodic porous alumina can be used many times. The obtained micro- and nanostructures will be useful for the fabrication of energy conversion devices with high efficiency due to their precisely controlled geometrical fine structures. 1. T. Yanagishita, K. Nishio, and H. Masuda, Appl. Phys. Express, 1, 067004 (2008). 2. H. Masuda and K. Fukuda, Science, 268, 1466 (1995). 3. K. Yasui, T. Morikawa, K. Nishio, and H. Masuda, Jpn. J. Appl. Phys., 15, L469 (2005). 4. T. Kondo, T. Fukushima, K. Nishio, and H. Masuda, Appl. Phys. Express, 2, 125001 (2009). 5. T. Yanagishita, R. Fujimura, K. Nishio, and H. Masuda, Langmuir, 26, 1516 (2009). 6. T. Yanagishita, Y. Maejima, K. Nishio, and H. Masuda, RSC Adv., 4, 1538 (2014).

New Pneumatic Rubber Leg Mechanism for Omnidirectional Locomotion

This paper describes a new pneumatic rubber leg mechanism for omnidirectional locomotion. The new mechanism was adopted from a pneumatic balloon actuator where translation and bending motions are produced as a result of balloon deformation. It was constructed using five chambers: one on the top and centered over four bottom chambers arranged in a square. Several possible designs were simulated to achieve the optimal design using a non-linear finite element analysis that considered the design parameters and the geometrical and material non-linearity of the elements. Prototyping was then performed using a rapid and efficient silicone rubber molding fabrication process based on computer-aided design and manufacturing. The experimental results were in good agreement with the analytical results. In conclusion, we have established a new rubber leg mechanism with a high degree of freedom to realize omnidirectional locomotion for a soft robot base, delicate object conveyance, and / or microscope stage applications.

Design, tolerance, and fabrication of an optical see-through head-mounted display with free-form surface elements

Free-form surfaces (FFSs) provide more freedom to design an optical system with fewer elements and hence to reduce the size and weight of the overall system than rotationally symmetric optical surfaces. In this paper, an optical see-through (OST), head-mounted display (HMD) consisting of a free-form, wedge-shaped prism and a free-form lens is designed and fabricated through the injection molding method. The free-form prism for the projection system is designed with a field-of-view (FOV) of 36°; the free-form lens is cemented to the prism for the see-through system to achieve a FOV of 50°. The free-form prism and lens are expanded at the edge area during the design stage in order to reduce the effects of surface deformation in the working area in molding fabrication process and to improve ergonomic fit with the head of a user. The tolerance analyzes considering the mold design for the free-form optical systems are carried out using the Monte Carlo method. The FFS optical elements are successfully fabricated and the system performance is carefully examined. The results indicate that the performance of the OST-HMD is sufficient for both entertainment and scientific applications.

Polymeric “smart” coatings to prevent foreign body response to implantable biosensors

Application of implantable glucose biosensors for “real-time” monitoring is reliant on controlling the negative tissue reaction at the sensor tissue interphase. A novel polymer coating consisting of poly(lactic-co-glycolic) acid (PLGA) microsphere dispersed in poly(vinyl alcohol) (PVA) hydrogels was evaluated in combination with dummy sensors as a “smart” drug eluting biocompatible coating for implantable biosensors to prevent the foreign body response, and thus enhance sensor performance in vivo. The polymeric microspheres slowly release tissue-modifying drugs at the implantation sites to control the inflammation and fibrous encapsulation, while the hydrogel allows rapid analyte diffusion to the sensing elements. Dummy sensors with identical dimensions to that of the functional glucose sensors (0.5×0.5×5mm) were coated with the PLGA/PVA composites using a mold fabrication process. Both normal and diabetic rats were used in the current study to investigate the effect of the diabetic state on tissue sensor interactions. It was evident that the PLGA/PVA hydrogel composite was able to form a uniform coating around the dummy sensor and stayed intact throughout the course of the study (one month). Tissue samples containing dummy sensors that were coated with dexamethasone free composites exhibited acute and chronic inflammation as well as fibrous encapsulation in both normal and diabetic rats. However, the diabetic rats exhibited decreased intensity and delayed onset of the foreign body response following implantation of drug free dummy sensors in comparison to those of normal rats. On the other hand, tissues containing dummy sensors that were coated with dexamethasone containing composites remained normal (i.e. similar to untreated tissues), with no inflammatory reaction or fibrous encapsulation occurring over the one-month period in both the normal and diabetic rats. The feasibility of utilizing PLGA microsphere/PVA hydrogel composites as coatings for implantable biosensors was demonstrated. This polymeric composite is an innovative approach to control the foreign body reaction at the tissue–device interface to prolong biosensor lifetime.

All-thermoplastic nanoplasmonic microfluidic device for transmission SPR biosensing

Early and accurate disease diagnosis still remains a major challenge in clinical settings. Biomarkers could potentially provide useful tools for the detection and monitoring of disease progression, treatment safety and efficacy. Recent years have witnessed prodigious advancement in biosensor development with research directed towards rapid, real-time, label-free and sensitive biomarker detection. Among emerging techniques, nanoplasmonic biosensors pose tremendous potential to accelerate clinical diagnosis with real-time multiplexed analysis, rapid and miniaturized assays, low sample consumption and high sensitivity. In order to translate these technologies from the proof-of-principle concept level to point of care clinical diagnosis, integrated, portable devices having small footprint cartridges that house low-cost disposable consumables are sought. Towards this goal, we developed an all-polymeric nanoplasmonic microfluidic (NMF) transmission surface plasmon resonance (SPR) biosensor. The device was fabricated in thermoplastics using a simple, single step and cost-effective hot embossing technique amenable to mass production. The novel 3D hierarchical mold fabrication process enabled monolithic integration of blazed nanogratings within the detection chambers of a multichannel microfluidic system. Consequently, a single hard thermoplastic bottom substrate comprising plasmonic and fluidic features allowed integration of active fluidic elements, such as pneumatic valves, in the top soft thermoplastic cover, increasing device functionality. A simple and compact transmission-based optical setup was employed with multiplexed end-point or dual-channel kinetic detection capability which did not require stringent angular accuracy. The sensitivity, specificity and reproducibility of the transmission SPR biosensor was demonstrated through label-free immunodetection of soluble cell-surface glycoprotein sCD44 at clinically relevant picomolar to nanomolar concentrations.

High-density pattern transfer via roll-to-roll ultraviolet nanoimprint lithography using replica mold

Roll-to-roll ultraviolet nanoimprint lithography (RTR UV-NIL) has attracted much attention as a high-throughput nanofabrication process. In particular, high-density nanoscale line-and-space (L&S) patterns are widely used for optical devices and printed circuits, such as wire-grid polarizers and transparent electrode films. To realize a simplified high-throughput RTR process, the authors developed a replica roll mold fabrication process and examined the feed speed of RTR UV-NIL. The replica mold was fabricated by applying parallel-plate UV-NIL using a silicon master mold with 100-nm L&S patterns and 200-nm groove depth. Replica molds were coated with 10-nm-thick tungsten and a fluorinated silane coupling agent to prevent the adhesion of UV-curable resin during RTR UV-NIL. The release-coated replica molds were wrapped around roll substrate having a diameter of 150 mm. Using the replica mold, RTR UV-NIL was carried out at different UV doses, which were determined as the product of the UV light intensity and feed speed. The results confirmed that a sufficient UV dose enabled successful pattern transfer, while an insufficient UV dose caused the pattern to break down. In this experiment, a rapid feed speed of 18 m/min was possible under conditions of high UV light intensity. In addition, the release agent was still active after 500 revolutions of the replica roll mold (235.5 m).

Nanoimprint Mold for 2.5 Tbit/in.2 Directed Self-Assembly Bit Patterned Media with Phase Servo Pattern

We demonstrate the mold fabrication and replication process for the production of 0.8 and 2.5 Tbit/in.2 directed self-assembly bit patterned media (DSA-BPM). These devices are fabricated with 33 and 17 nm dot pitch patterns using the microphase segregation structure of polystyrene–poly(dimethylsiloxane) as an etching mask template. The self-assembled dot arrays are simultaneously ordered on both the circular tracks for the data area and the arbitrary marks for the servo area by DSA using groove guides. We fabricated the Si mold with dot pillars of 19.3 nm height for the 2.5 Tbit/in.2 DSA-BPM from the poly(dimethylsiloxane) dot mask. We also demonstrated the nickel mold replication of the 0.8 Tbit/in.2 DSA-BPM by electroforming from the Si mold.

Technical Development on Rapid Green Silicone Rubber Mold

Rapid tooling technology is regarded as an important approach of reducing the cost and time to market for new products. Silicone rubber mold is frequently employed in the indirect tooling. Based on green manufacturing, a green silicone rubber mold fabrication process is developed and implemented in this work. This method provided a new, simple and green manufacturing to produce silicone runner mold. The advantages of this method include high yields of the mold fabrication, reducing the cost in the mold fabrication and environmentally conscious manufacturing. The saving in the cost of silicone rubber mold fabrication is up to 35.66 %.

Seamless long line and space pattern fabrication for nanoimprint mold by using electron beam stepper

Nanoimprint lithography (NIL) is a simple process to fabricate nanostructure devices with high throughput and low cost. The mold fabrication process is an important factor to improve NIL technology. Adopting a seamless pattern mold fabrication process is expected to enhance throughput. In this study, we developed a seamless long line and space (L and S) pattern fabrication process by using an electron beam (EB) stepper. As a result, a seamless 200nm line and 300nm space pattern (120mm long and 10mm wide) was exposed on a 6in. Si wafer. We also carried out thermal nanoimprinting using the seamless L and S pattern mold fabricated by using the EB stepper. We confirmed that the seamless L and S pattern was clearly imprinted on the resin.

Mass-producible superhydrophobic surfaces

Mass-producible superhydrophobic surfaces with remarkably identical appearance and efficiency through a mold fabrication and hot embossing process are reported.

Impact of substrate deformation on demolding force for thermal imprint process

The impact of deformation on the demolding force is investigated both experimentally and by simulation for the thermal imprint process. The effects of substrate thickness are the focus of this article. In experiments, one mold is used throughout all experiments in order to exclude any effects of the mold fabrication process. The mold pattern is transferred to a polymethylmethacrylate (PMMA) film by the thermal imprint. The PMMA surface height is measured by a commercial height profiler after the imprint, and it agrees with lateral variations in residual layer thickness. Demolding force increases as substrate thickness increases. Substrate deformation is simulated by simplifying a model to assume the presence of large cavities. Substrate deformation in the simulation agrees with the PMMA surface height profile in the experiment. The normal force to the PMMA side wall by the mold pattern is important for estimating the demolding force. Since the normal force during the pressing process is simulated, the normal force is induced by both the lateral expansion of PMMA resin and substrate deformation. The normal force from substrate deformation is selected based on a detailed analysis of the simulated normal force. The obtained normal force agrees with the demolding force in the experiment.