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A new apparatus for a moving induction heating and gas-assisted hot embossing apparatus has been developed. A mechanism was designed and implemented to move the platform in and out the wrapped coil, on which the sealed box for substrate/mold was placed. A chamber of 195 mm diameter and 221 mm length was machined. The movable platform, the sealed box with substrate/mold stack, wrapped coil and cooling fan were all implemented in the high pressure chamber. The nine-point thermocouples attached on the mold, thus, a temperature history of the moving induction heating can be obtained and study the influence of the moving path and power on the heating rate and temperature distribution. The micro V-cut structure hot embossing experiment were performed to prove the potential of this moving induction heating and gas-assisted pressuring hot embossing for fast fabrication of microstructure onto polymeric substrates. As a results, replication rates were all above 95% at 200 °C and 5 kgf/cm2 and the cycle time was less than 4 min and the optic measurement shows the replicated V-cut film can enhance the 36.8% illuminance. The experiment results show the manufacturing potential of this apparatus.

In this study, the ultraviolet (UV) curing and air pressure imprinting methods are proposed for the fabrication of a light-intensity-enhancement component. The air-pressing process provides a uniform embossing pressure, and the UV curing module enables the process to be performed at room temperature and low pressure. Because the UV resin is sensitive to the process parameters, such as the curing time and pressing pressure, the liquid resin must be filled at a precise pressure. To control the precision, the UV embossing facility comprised a resin-dispensing system, air-pressing system, and UV curing system. These systems were controlled by the Arduino system. In the Arduino system, the computer-controlled input can eliminate artificial errors and each forming step can be programed into one script to achieve automation. In this study, V-groove microstructures were formed. The V-groove pattern was replicated with a width of 47 μm and height of 22 μm on polymethyl methacrylate substrate for use as a light guiding panel. The proposed methodology enables automatic control of the UV microscale imprinting process.

UV roller imprinting is one of the most efficient mass-production processes for microstructure replication. Roller imprinting of microstructure on both top and bottom surfaces of substrate is challenging. The imprinting pressure has to remain uniform. Furthermore, it is difficult to irradiate UV light if both molds in the top and bottom are not transparent. In this study, air bearing was used to pressurize the top mold, which resulted in uniform non-contact pressure. UV light was irradiated from the lateral of the transparent substrate. An UV roller imprinting apparatus with air bearing pressing and lateral irradiating of UV light was designed and implemented. Pressure distribution measurements with pressure sensitive film proved that the air bearing provided a uniform imprinting pressure over a large area. V-groove microstructures with micrometer precision have been successfully fabricated on both sides of poly (methyl methacrylate) (PMMA) substrates over 98% replication rate. This study demonstrated lateral-irradiating, air bearing assisted UV roller imprinting has great potential for production of optical components with microstructures on both surfaces.

This study proposed an innovative imprinting process technology for the compound casting of a steel shim and poly-dimethylsiloxane solution. The resulting solid magnetic sheet has angular asymmetric changes. Electromagnet-assisted imprinting technology and ultraviolet lamp light curing equipment were used to reproduce a micro-lens structure of different linear gradient molding heights from the original even micro-lens mold by imprinting. Hence, in a single imprinting process, using the same mold to reproduce micro structures of different heights, with controllable and predictable heights of linear gradient, this study developed a simple and low-cost innovative processing technology on the basis of electromagnetic imprinting and compound casting in order to provide an effective alternative for imprinting processes and applications in the broad sense. For result validation, this study used the pressure sensitive soft mode to discuss the distribution of the imprinting force of the asymmetric linear gradient sheet shim using scanning electron microscope, a surface profiler, and other instruments to observe, measure, and analyze the process results.

This paper proposes an advanced microstructure embossing replication technology that combines an electromagnetic-field-aided magnetic soft mold and a reverse imprinting technology to replicate microstructure. The main advantage of this technology is low pressure, low cost, and quick and easy forming. The entire imprinting process can be completed at room temperature using a ultraviolet (UV) curing technique. This study applied a compound casting technique to fabricate a magnetic poly(dimethylsiloxane) (PDMS) soft mold, with an electromagnetic chuck for even imprinting pressure, and reverse imprinting molding technology. Microstructure cavity of the mold was fully filled with photoresist before imprint replication, and improved microstructure transfer ratio. Examination of the results showed that, the magnetic PDMS soft mold integrated electromagnetic-field-aided reverse imprinting process developed by this study, can successfully replicate microstructure at room temperature, low pressure, and avoid deform...

The transfer stamping process has been used to fabricate thin-film pattern in recent years. Due to the characteristics of the materials of molds and inks, residual inks on the cavities of mold and residual layers on the substrate are still a problem. To solve the problem, we present a concept for fabrication of hydrophobic nanostructures on the cavities of microstructures of the mold, which can effectively decrease the ink residing on the cavities of the mold during coating. First, the periodic nanopores are fabricated on the anodic aluminum oxide (AAO). Second, AAO membrane is employed as the template for fabricating nanostructures on the PC film by embossing. And then, by partial protrusion of the nano-structured PC film into the micro-holes of the mold, an array of protruded convex microstructures is formed. After that, polydimethylsiloxane (PDMS) mold is casted from the embossed PC film. The contact angle of nanostructures on the micro-cavities of PDMS mold is about 145^o. Micro-patterns with no residual layers have been successfully transferred on the poly(ethylene terephthalate) (PET) substrate using a transfer stamping process with this PDMS mold.

This study proposed a novel technology, which uses exposed technology with ultraviolet light-emitting-diode (UV-LED) arrays and the polydimethylsiloxane (PDMS) magnetic flexible soft mold imprint technology, to develop exposed equipments with UV-LED arrays. This study used magnetic soft mold imprint technology to replicate the structure of microlens, providing a more effective alternative for imprint technology and application. The measurement results showed that PDMS with magnetic iron powder can precisely cast mold to replicate the structures of microlens. Electromagnetic plates were used to control even imprinting with magnetic force, in order to fill the mold of micro-structure of the photo-resist. Magnetic iron powder was added to PDMS to produce composite material, which can effectively avoid the transformation of pure PDMS during soft mold imprinting, and increase mechanical strength. Magnetic PDMS soft mold is easy to make, and the casting time is short, so that costs can be effectively reduced. Also with advantages of less free energy on its surface, and unlikely to adhere to the photo-resist during imprinting, it can be combined with electromagnetic plates evenly to control the magnetic soft mold. This imprinting technology is a big advantage to the production process of micro-structures during imprinting. Copyright © 2009 John Wiley & Sons, Ltd.

This paper discusses an innovative and effective ultrasonic embossing process, which enables the rapid fabrication of surface-relief plastic diffusers. The metallic mold bearing the microstructures is fabricated using a tungsten carbide turning machine. A 1500-W ultrasonic vibrator with an output frequency of 20 kHz was used to replicate the microstructure onto 1-mm-thick PMMA plates in the experiments. During ultrasonic embossing, the ultrasonic energy is converted into heat through intermolecular friction at the master mold/plastic plate interface due to asperities to melt the thermoplastic at the interface and thereby to replicate the microstructure. Under the proper processing conditions, high-performance plastic diffusers have been successfully fabricated. The cycle time required to successfully fabricate a diffuser is less than 2 s. The experimental results suggest that ultrasonic embossing could provide an effective way of fabricating high-performance plastic diffusers with a high throughput.

In this study, we report the micro-injection molding of ultra-thin parts (100, 250, and 500 µm). The results show that the flow resistance increases as the cavity becomes thinner. The melt front is not symmetric when filling a four-cavity ultra-thin part and filling the eight-cavity mold under a low temperature. If we increase the mold temperature or cavity thickness, the melt front becomes symmetric. Finally, we construct the operation windows of molding for three kinds of plastics (PS, PMMA, PC) and provide a molding range based on mold temperature and injections speed. Meanwhile, the relationship between the thickness and the operation windows are also investigated. The thinner the cavity is, the smaller the operation window is. We need to increase the injection speed significantly for molding the ultra-thin parts with micro-features on both surfaces which are 60 µm in thickness. Furthermore, we succeed in molding 30 µm ultra-thin parts in this experiment. Copyright © 2009 John Wiley & Sons, Ltd.

Roller embossing has attracted more attention in recent years due to its rapid and continuous process for mass production. The fabrication of roller is a challenge due to microstructures on the curved surface. This paper proposes a method of fabricating roller mold with microstructures on the surface using novel stepped rotating lithography and electroless nickel plating. The results prove that the microstructures can be successfully fabricated onto the metal roller using the proposed procedure. In this study, the roller with micro-grooves whose average height is [email protected] and widths are 23 and [email protected] have been successfully fabricated.

Replication of microstructures from a mold onto a curved surface is difficult. The conformal contact between the mold and the substrate has to be ensured. The present study proposes an innovative mechanism, which employs an electromagnetic disk to provide magnetic force and a PDMS flexible mold with a layer compounded magnetic powder. This mechanism provides not only the gradual contact from center to edge to avoid air entrapment but also conformal contact between the mold and the substrate during the imprinting operation. A system based on this electromagnetic soft imprinting technology has been implemented, and imprinting to replicate microstructures from the mold onto a curved surface has been carried out. The results reveal that the PDMS magnetic mold and the electromagnetic disk-controlled magnetic force can successfully perform the imprinting and accurately replicate the microstructures onto the large-area, curved surface glass. The PDMS flexible magnetic mold incorporated with the magnetic disk can be employed to achieve the conformal contact between the mold and the substrate. In addition, due to the low surface free energy of the PDMS, the de-molding without sticking can be easily accomplished. Copyright © 2008 John Wiley & Sons, Ltd.

In this study, we develop a vacuum-assisted photo resist filling technology for micro-structures by integrating the characteristics of PDMS soft mold, photo cure resist, and vacuum equipment. Together with soft mold, this technology can be adopted in the production of optical waveguide components. Conformal contact can be achieved on the material surface with PDMS soft mold. Meanwhile, it has a low surface free energy and won't stick to the resist during the filling. By vacuum pumping, the resist filling will be compact and complete. It increases the effective filling area significantly.

Multi-cavity injection molding has been regarded as low cost mass-production method for producing plastic products such as optical elements. However, the flow imbalance during filling a multi-cavity mold using symmetrical runner system is a serious problem. This paper is devoted to improving the flow balance by modifying the runner system design. For this purpose, four eight-cavity molds with four modified symmetrical runner systems are designed, constructed and tested. They are tapering H-type runners, pinned H-type runners, curved A runners, and curved B runners. The flow imbalance in each runner system is observed and measured with the aid of short-shot experiments. The experimental results indicate that the tapering H-type runner system can improve flow balance. The pinned H-type runner system fails to improve flow balance. The curved A and B runner system can reverse the imbalance trend, but the stability of the curved systems is poor at high melt temperature.

The present study employs an innovative technique, which uses PDMS soft mold, blended with magnetic powder as the transmission and imprinting methods, and integrates features from soft micromolding PMMA, an electro-magnetically controlled, well-proportioned, pressing technique in order to study how to create microlens arrays through a magnetic soft mold imprinting resist technique. Thus, it renders nanometer imprinting applications, and its technology, more developed and mature. The research findings revealed that, PDMS, blended with magnetic powder, can accurately recast and duplicate nanometer microstructures. Under well-proportioned magnetic pressing, controlled by an electro-magnetic disk, it can effectively fill and shape resist microstructures. The composite material of PDMS, with added magnetic iron powder, can effectively improve mechanical strength properties of pure PDMS soft mold, which is easily transformed for imprinting. Meanwhile, owing to the unique features of PDMS soft mold, conformal contact with the base material is possible; therefore, the effective imprinting area and the duplicated representation are significantly improved. In addition, as magnetic PDMS soft mold is easily produced and fast in recasting, the costs can be effectively reduced. In addition, due to features such as low surface free energy and a tendency not to stick to resist in imprinting, the soft mold is evenly controlled by the electro-magnetic disk for imprinting duplication, highlighting the advantages of microstructure imprinting procedures. Copyright © 2008 John Wiley & Sons, Ltd.

This article reports an effective method for mass-production of 300 × 300 microlens arrays. A microlens array master is formed by imprint lithography and photo-resist reflow at room temperature. The electroforming is then applied to fabricating the Ni mold from the master, followed by the gas-assisted hot embossing to replicate the microlens arrays. The isotropic gas pressure on the plastic film against the Ni mold produces plastic microlens array of high quality and uniformity. The effects of processing parameters including the processing temperature, pressure, and time on the replication quality of microlens arrays were investigated. The experimental results show that the filling of molded microlens significantly increases as the processing temperature and pressure increase. Under the condition of 180°C, 3.9 MPa for gas pressure, and 90 seconds processing time, the arrays of polycarbonate microlens of diameter 150 µm and pitch 200 µm have been successfully replicated. The deviation of replicated microle...

This study reports the experimental investigation on the flow imbalance phenomena during filling symmetrical multi-cavity in injection molding of optic elements. There are two aspects in this study: First, the flow imbalance in the eight-cavity mold with normal H-type symmetric runners were observed and measured with aid of short-shot experiments. Second, the effects of three processing conditions including injection speed, melt temperature and mold temperature on flow imbalance were investigated. Flow imbalances are consistently observed and quantitatively measured. The results have shown that proper injection speed, high melt and high mold temperature can reduce the flow imbalance.

Wavelength limitation and diffraction of light are the bottlenecks encountered in the production of structures by conventional lithography. Nano-imprinting has been a potential process for mass production of nanometer structures at low cost. This paper reports an innovative process to replicate the ridge-shaped microstructures on the silicon mold onto the photoresist using gas-assisted pressing mechanism and soft mold. The microstructures on the silicon mold are replicated unto PC films. The soft mold is obtained by casting the PDMS with the PC film as templates, PDMS mold and UV-curable photoresist are brought into contact, and are pressurized by gas and cured by UV-light at the same time. After curing, structures for optical wave guilding can be obtained, In this process, through the control of gas pressure, the residual layer of the ridge-shaped component for light guilding can eliminated. Etching is no longer needed to get rid of the residual layer. This process is effective for mass production for replication of microstructures at low cost. Copyright © 2007 John Wiley & Sons, Ltd.

This paper reports an innovative technique for rapid fabrication of polymeric microlens arrays based on UV roller embossing process. In this method, a thin flat mold is fabricated by electroforming of nickel against a microlens master. The thin Ni mold with microlens cavities is then wrapped onto cylinder to form the roller. During rolling operation, the roller pressing and dragging the UV-curable photopolymer layer on the glass substrate through the rolling zone, the microlens array is formed. At the same time, the microlens array is cured by the UV light radiation while traveling through the rolling zone. The technique can be developed to an effective roll-to-roll process at room temperature and with low pressure. In this study, a roller embossing facility with UV exposure capacity has been designed, constructed and tested. Under the proper processing conditions, the 100×100 arrays of polymeric microlens, with a diameter of 100 μm, a pitch of 200 μm and a sag height of 21 μm can be successfully fabricated.

This paper presents an integrated high temperature ultrasonic transducer (HTUT) on a sensor insert and its application for real-time diagnostics of the conventional hot embossing process to fabricate V-cut patterns. The sensor was directly deposited onto the sensor insert of the hot embossing mold by using a sol-gel spray technique. It could operate at temperatures higher than 400 °C and uses an ultrasonic pulse-echo technique. The ultrasonic velocity could indicate the three statuses of the hot embossing process and also evaluate the replication of V-cut patterns on a plastic plate under various processing conditions. The progression of the process, including mold closure, plastic plate softening, cooling and plate detachment inside the mold, was clearly observed using ultrasound. For an ultrasonic velocity range from 2197.4 to 2435.9 m/s, the height of the V-cut pattern decreased from 23.0 to 3.2 µm linearly, with a ratio of −0.078 µm/(m/s). The incompleteness of the replication of the V-cut patterns could be indirectly observed by the ultrasonic signals. This study demonstrates the effectiveness of the ultrasonic sensors and technology for diagnosing the replicating condition of microstructures during the conventional hot embossing process.

The micro-injection molding is used to fabricate ultra-thin polymeric components used in optoelectronics and biotechnology. Due to the extremely high flow resistance and fast heat transfer, ultra-thin parts is difficult to mold. In this study, a lab-made impact type micro-injection machine and a rapid heating/cooling system are used to perform the micro-injection molding. A mold with test-sheet cavities of thickness 100 μm and 200 μm are constructed. The molding capacity and the effects of processing conditions are systematically investigated. The processing conditions include the mold temperature, air pressure of accelerating cylinder, and air pressure of packing cylinder. The thicker parts have larger operation window. The high mold temperature reduces the area of short shot but induces more shrinkage and sink mark. The increase of air pressure in accelerating and packing cylinders can effectively reduce shrinkage.

In this paper we report a simple and effective method that renders direct imprinting of sub-micron structures onto PMMA resist coated on large area and curved substrates using the PDMS mold on a closed chamber. Nitrogen gas was employed to generate a uniform pressure. The patterns of the soft mold could be replicated with high quality over an entire 12in. resist-coated area. The process was further successfully applied to the imprinting of a curved substrate.

This paper presents the application of injection molding of wedge-shaped plates for lightguiding application. This paper discusses the influence of processing parameters on injection molding. The filling stages of lightguide plate for mold flow simulation (3D, midplane) are analyzed. The numerical simulation of mold filling process is based on the concept of control volume finite element method. The hot plastic melt touches the cold wall that forms the solid layer, a solid-liquid interface moves and a two-phase flow exists. The enthalpy model is used to predict this interface in the two-phase flow problem. The experiments carry out short-shots process to compare with numerical simulation. The experiments also indicate the pressure distribution at thin and thick ends of lightguide plate using pressure transducers. The results show that the results of 3D filling situation is close to those from experiments. The melt front progress of 3D numerical simulation is predicted more accurately than midplane numerical simulation.

This paper investigates the fracture types and thickness ratio distribution in superplastic Zn/Al sheets formed during a hybrid process combining superplastic sheet forming with plastic injection molding. Three types of sheet fractures, edge cracking, central cracking and combined cracking, are observed. The success of forming superplastic sheets with rib features using injection molding with various parameters, including melt temperature, injection pressure and mold temperature, are investigated. They are presented in the form of a molding area with areas of various fracture types. Central cracks occur when superplastic sheets are formed with injection molding with higher melt temperature, while edge cracks occur with higher injection pressure. When the melt flow is parallel to the sheet rolling direction, the areas of edge crack are enlarged. The sheet thickness ratio distribution is obtained for various injection parameters and rib depths. Observation of the sheet thickness distribution for variation parameters, the tendency of the sheet fracture type can be generalized.

High quality advanced composite tools (ACTs) have been introduced to the growing tooling market. Since ACTs are used for high precision composite parts, even minor warpage in a tool might render the parts useless. Trial and error in making or remaking an accurate ACT are time-consuming and expensive. This paper is devoted to investigating the effects of processing on the accuracy of ACTs for slanted shapes. An experimental design based on the Taguchi Method is employed. The experimental parameters investigated are postcure, mold material, laminate thickness, cure temperature, preheat, bleeder, pressure, and caul sheet. Warpage is used to verify the accuracy of ACTs. Optimum processing conditions and critical parameters have been found. The warpage that results under optimum processing conditions decreased significantly. Based on the findings in fiber volume fraction gradients, the observed convex and concave angle differences in warpage can be explained. To overcome the tendency to warpage, by means of an asymmetric doubler or insert in angle corners, a proper amount of asymmetry is implemented, which successfully improves the accuracy of the ACT shape.

Injection molding is now used to mold plastic parts with precision contours such as lenses. Cooling conditions have critical effects on the quality and productivity of such precision parts. This article is devoted to investigate the effects of mold temperature and cooling time on quality. A two-cavity mold for molding convex lenses with square-looped cooling channels was used. Samples molded with different mold temperatures and cooling times were collected, and their contour conformity to those of the cavity was evaluated. Contour errors were defined. The correlation between mold temperature and cooling time and contour errors was analyzed. It has been found that for a given mold temperature, two critical cooling times can be defined at which the thermal and rigidity states pass through a transition. Most dramatic improvements in part conformity occur around such critical points. © 1996 John Wiley & Sons, Inc.

Mold temperature is one of the most important factors regarding the quality and production rate in injection molding. Enhancing the performance of mold as heat exchanger is expecially critical to precision molding. In this study, mold temperatures measured at four selected points are used to assess the effects of cooling channel layout and core material on the cooling performance of injection molds for precision molding. Measured data indicate that mold temperature is a complex function of space and time (in-cycle and cycle-to-cycle). Three performance indices based on the measured data are first established for comparing the cooling performance between molds with various design parameters. They are the response to reach equilibrium, the thermal uniformity, and the average mold temperature. Molds implemented with three typical cooling channel configurations and inserted with three core materials are constructed. Their cooling performances during injection molding of disks with steps have been compared. Information from computer-aided simulation of the mold cooling process further facilitates the evaluation of mold cooling performance. General guidelines for planning of cooling channel layouts and selection of core materials are drawn from this study. Experimental and theoretical results suggest that high thermal conductivity of the cores enhances the thermal uniformity, while high heat capacity retards the response of the system to reach thermal equilibrium. High convective area to mold volume improves the overall performance of mold as heat exchanger.

A modified injection molding machine with a compression mechanism, and a mold with a movable wall and shut-off mechanism, were used to investigate the effects of processing parameters on the quality of injection-compression-molded polystyrene disks. The compression start-up time, compression force, melt temperature, and part thickness were selected processing parameters. The disk moldings were evaluated based on dimensional accuracy and birefringence. It is found that the compression start-up time affects packing time, and thus greatly affects the residual orientation. If the transition from packing to compression could start before peak cavity pressure, disks with low residual orientation could be obtained. High compression force improves part quality and reduces thickness. Since both compression-induced reduction and cooling-induced shrinkage are involved, the effects of temperature and thickness are not as straightforward as the trends in conventional injection molding.

Gas-assisted injection molding (GAIM) has proven itself to be a breakthrough in molding technology. However, the process involves additional gas-related parameters to control the molding process. The interaction between melt and gas makes the gas-assisted process complicated. To make satisfactory parts, the material, the mold, and process parameters determine the “moldability” of a specific system. The concept of “molding areas” on the critical plane can be extended from thermoplastic injection molding to GAIM. This research is devoted to the development of a proper moldability diagram for GAIM. The first part of this study employs gas-related parameters to define the molding area. The second part is devoted to identifying the relative importance of process parameters. The results show that melt temperature and short shot are the two factors which most significantly affect the GAIM process. The third part of this study defines the moldability based on critical parameters. The application of the moldability concept is demonstrated in selecting the optimum rib geometry. These moldability studies are intended to give first guidelines for system optimization. © 1995 John Wiley & Sons, Inc.

This paper reports a novel and effective method to fabricate microlens arrays on polycarbonate films by hybrid extrusion rolling embossing. The metallic cylinder mold bearing an array of micro-holes is fabricated using photolithography with dry film resist. During the extrusion rolling embossing process, the extruded PC film is immediately pressed against the surface of the roller mold. Under the influence of the rolling pressure and surface tension, an array of convex microlenses is formed. The uniformity and optical properties have been verified. An efficient continuous mass production technique has been demonstrated.

This paper reports a simple and effective method to fabricate microlens arrays with the ultraviolet-curable resins, and a soft mold of micro-holes array. During capillary forming operation, the surface of the soft mold of micro-holes array is being pressed against the ultraviolet-curable resin layer coated on the plastic substrate. An array of convex lense can be formed in the circular holes of the soft mold due to the capillary filling and surface tension. The microlens arrays have smooth surface and uniform focusing function. The shape and height of micolens can be controlled with a proper combination of pressing pressure, pressing duration and UV curing dose. This technique shows great potential for fabricating polymer microlens arrays with high productivity and low cost.

This study proposes a novel technology using nano-particle fluid electromagnetism to control the direct hot imprint resist of nickel mold. combining the present gas-assisted nanoparticle hot imprint molding technology, electroforming technology, and self-designed heatable electromagnetic plate for even control and progressive pressuring technology, this study used electromagnetic nickel mold direct hot imprint to replicate micro structures, in order to make the molding technology and application of micro nanoimprint more mature. This study first used gas-assisted nanoparticle hot embossing method to replicate structures of microlens of original silicon molds on PC, so as to obtain complementary structural patterns. This PC film with structures of microlens is cast into nickel molds by electroforming. This nickel mold was used as the mold for magnetic embossing to imprint hot plastic PMMA.The result showed that through gas-assisted nanoparticle hot embossing molding, casting and component magnetic PDMS soft mold casting, molds of high costs and complicated production process can be massively replicated, and the replication precision is good. Hot gas embossing PDMS film and the surface of base materials can achieve even pressure and conformal contact, thus significantly improving the effective imprint area and imprintability. Through electroforming, casting duration of magnetic nickel molds can be shortened and costs can be effectively lowered. Moreover, electromagnetic plate was used to evenly control the direct hot pressure imprint resist, which is an advantage of the production process of micro structures.

A creative technology was used in this research. Using the PDMS flexible mold magnetic powder method to transmit imprinting, and by combining the special characteristics of the soft lithography, polymethylmethacrylate (PMMA), and electromagnetic Plate uniform control pressing technology, researching the use of magnetic flexible mold imprinting technology to produce the optical waveguide devices, so as to allow the usage and the technology of micro hot embossing or nanoimprinting more mature.

Large-area microlens arrays are becoming important components in many applications such as LCD-TV diffusers. This paper reports a uniform pressure, low temperature process for their fabrication. The process integrates gas-assisted embossing and UV-curing embossing. During the process, the 230mm x 203mm PMMA substrate is pressed against the stainless-steel stamper coated with UV-curable resin. Under the gas pressuring and UV irradiating, a large array of microlens can be formed. By using this process, high embossing temperature and high embossing pressure can be avoided. Little residual stress is observed in the embossed PMMA substrate. The uniformity of large-area fabrication and optical properties of fabricated resin microlens array have been verified. This study has successfully shown the potential of this gas-assisted UV embossing process for the replication of large-area microstructures.

Most plastic diffusers are either of surface-relief or particle-diffusing types, based on different principles and fabrication methods. This paper reports an innovative extrusion roller embossing process, which enables the fabrication of diffusers with both surface-relief and particle-diffusing functions. An extruder with die is employed to fabricate the thin film of PC/bead composite; the roller micro-embossing process is used to replicate the microstructure onto the surface of PC composite film. A metallic roller mold with microstructures is fabricated using turning process. During the extrusion rolling embossing process, the extruded film of PC with diffusion beads is immediately pressed against the surface of the roller mold. Under the proper processing parameters, the plastic diffusers integrating surface-relief and particle-diffusing functions have been successfully fabricated. The shape, uniformity, and optical properties of fabricated diffuser have been verified. This method shows the great potential for continuous fabrication of high-performance plastic diffusers integrating surface-relief and particle-diffusing functions with high throughput.

Glass is an excellent material for optical devices requiring optical and mechanical properties better than those of a polymer. Because traditional micro- or nano-fabrication on glass substrates is typically slow and costly, the fabrication of micron- or nanometer-scale structures on glass has been a challenge. For a novel continuous fabrication of glass microlens arrays with antireflective nanostructures (AR-MLA), we have designed and implemented a hot-rolled embossing facility with synergetic heating. The mold of a hybrid micro/nanostructure was fabricated in two steps. First, a micron-scale lens cavity was embossed on a nearly pure aluminum sheet with an electroplated nickel mold; an anodic aluminum-oxide process was used to create a nanostructure on the microlens array cavity. The mold was then mounted on a roller and used in a hot embossing machine to fabricate AR-MLA on optical glass. The optical properties of the fabricated microlens with nanostructures have been verified. The image of focused spots of fabricated AR-MLA shows an effective converging ability, and the reflectance at 550 nm was decreased from 7.63 % to 0.53 % with the fabricated nanostructures. This proposed technique has proven its potential for hot-rolled embossing of glass components with micro/nanostructures.

In the conventional imprinting process, the substrate and the stamp are brought into contact and compressed directly by the plate and rigid mold. However, replicating microstructures onto a nonplanar surface is difficult due to the limited contact area and nonuniform pressure. In this study, a gasbag-assisted UV imprinting process and a flexible polydimethylsiloxane mold are employed to replicate microstructures onto a cylindrical surface, using gas to enhance the closeness of contact and uniformity of pressure during imprinting. A gas-assisted UV-based imprinting facility, which contains a gasbag, air pressure system, motor driving system, and exposure system, is designed and implemented. V-cut microstructures are imprinted on the inner surface of the cylindrical PMMA substrate. The optical performance and brightness enhancement are then verified.

Air bubble defects have been regarded as a critical problem in ultraviolet (UV)-based imprinting/embossing processes, especially in large area fabrication. This paper reports a gas-assisted UV embossing process for bubble-free replication of large area microstructures. This gas-assisted pressurizing process provides uniform embossing pressure over the whole large area, while UV curing enables the process to be performed at room temperature and low pressure. To overcome the problem of air bubble entrapments in the large area UV embossing process, the mechanisms of modified reversal imprinting and gap-retained vacuuming have been developed and used. Experimental results show that the microstructures have been successfully transferred from the stamper to the polymethylmethacrylate substrate with the size of 230 × 203 mm2 inducing no air bubble defects.

In this study, we integrate the electromagnetic soft mold imprint technique with the electrophoretic deposition technique, and apply them to forming microelectrode structures. The compound casting technology is used to produce a magnetic soft mold of a microelectrode structure, which can effectively reduce the time and cost of molding. The use of an electromagnetic imprint device can apply more evenly distributed imprint pressure, thus, the microelectrode structure can be entirely imprinted onto an indium tin oxide (ITO) soft substrate, and then the electrophoretic deposition technique is employed to deposit titanium dioxide (TiO2) nanopowder on the ITO soft substrate of the microelectrode structure. In addition to the key techniques and processes of electromagnetic soft mold imprinting, In this study, we explore the application of electrophoretic deposition and imprinting to prove that combining these techniques to form a microelectrode structure is a simple, low-cost, high duplication, and high-speed process. It is proven a good choice for producing micro-nanocomponents.

Roller imprinting has been one of the most effective replication techniques due to its continuous nature and mass productivity. To improve the pressure uniformity and enhance the replication precision, a novel gasbag-roller-assisted UV imprinting process is designed and developed in this study. A belt-type polydimethylsiloxane (PDMS) mold with cavities for forming a microlens array is prepared. A gasbag roller is employed to exert pressure on the contact area between the PDMS mold and a PMMA substrate. Due to the isotropic pressure provided by the gasbag roller, the contact area between the mold and the substrate is increased and the uniformity of the imprinting pressure is enhanced. Precise replication and complete UV curing are thus achieved. A gasbag-roller-assisted UV-based imprinting facility is constructed, and the experiments are conducted. The results prove that a microlens array can be successfully fabricated on a 2 mm thick PMMA substrate. The shape profile and optical property of the microlens are also evaluated.

This paper reports a novel and effective method for the fabrication of a polymeric nano/micro hybrid lens array. The nanostructure and microlens arrays are fabricated on the same polycarbonate (PC) substrate by hot embossing in sequence. First, an anti-reflection PC film with sub-wavelength nanostructures is fabricated using an anodic aluminum oxide (AAO) template. The anti-reflection characteristic of nanostructures on the PC film is evaluated. Then an array of convex microlenses is formed from the nanostructured PC film using a stainless steel mold with a microhole array. Both processes employ gas-assisted hot embossing to perform the partial protrusion of the film into nano-sized or micro-sized holes in the AAO template and steel mold. The optical property of the microlens has been verified. This proposed technique has proven its potential for effectively fabricating a nano/micro hybrid lens array on a polymeric substrate.

This article reports a novel hydrostatic pressure mechanism for soft UV imprinting. With this mechanism, the pressure distribution over the whole substrate is uniform. In addition, the nonuniform deformation of the soft mold during the imprinting process can be avoided. The mechanism employs a gasbag inside a closed chamber, which upon inflation compresses the whole polydimethylsiloxane (PDMS) mold/substrate stack not only from the surface but also from all the sides. The microstructures on the PDMS mold are then replicated onto photoresist-coated substrates. The result shows that the soft UV imprinting using a hydrostatic pressure mechanism can provide uniform pressure for imprinting. It also provides the hydrostatic pressure state on the stack so that micropatterns can be replicated with high fidelity from soft mold to photoresist on substrates. The accuracy of replication, even at the edge, has been experimentally verified.

A gasbag pressure (GBP) mechanism has been developed for patterning submicron patterns onto large concave substrate. The GBP mechanism consists of a pressure gasbag and a vacuum chamber system. It provides gradual contact, uniform pressure, and intact contact for imprinting patterns in the soft mold onto a concave substrate. The patterns on the soft mold can be successfully replicated over an entire photoresist-coated concave substrate. The accuracy of replication has been experimentally evaluated.