Search

In this study, an easy and low-temperature differential hollow roller using an ultra-thin heating element of graphene polymeric composite material by wire bar coating technique was first demonstrated and fabricated successfully. In contrast to the conventional hot roller, this study confirmed the flexibility of high uniform temperature distribution in the rolling system. The dynamic-state temperature differential of four quarter positions and horizontal positions can be controlled within 2.8 °C and 1.2 °C with a voltage of 40 V, respectively. High-Temperature stability of long-term steady-state temperature was confirmed and the voltage only needs 25 V to get a steady-state temperature of almost 160 °C.

Using the optimal solution and aging treatment for Ti-6Al-4V brazed by Ti-15Cu-15Ni and Ag-26.7Cu-4.5Ti fillers, the average shear strengths of the lap-joint interface are improved. And the average grain sizes and the average lengths of Widmanstätten structure are significantly smaller than that of post-brazed annealing. Both fillers specimens are examined to indicate the strengthening mechanism is to homogenize the microstructure of Ti-6Al-4V joints to simultaneously enhance the strength of joint braze and substrate.

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.

UV imprinting has been one of the most productive replication techniques due to its low imprinting pressure and temperature. The conventional UV resin is cured by direct irradiation from the bottom. Space management and energy consumption become problems as the areas are getting larger and larger. Another problem is the uniformity of imprinting pressure, which is higher near the center with conventional platen-pressuring imprinting. In this study, we develop an innovative side-emitting UV-curing gasbag-pressuring imprinting mechanism for large area microstructure replication. An imprinting system based on such integration has been designed and implemented. V-groove microstructures has been imprinted onto a PMMA plate with dimensions of 380 mm × 230 mm × 3 mm for light enhancement. The optical performance and the profile of microstructures have been verified.

Polydimethylsiloxane (PDMS) is an excellent soft mold material with the advantages of precise replication, easy demolding, and low production cost. However, the strength and hardness of PDMS are relatively low, and PDMS cannot be directly inductively heated. In this study, PDMS is embedded with ferromagnetic powders to increase its hardness and make it heatable. Direct induction heating of the PDMS mold can raise its inherent temperature, increase the heating efficiency by 100% compared with pure PDMS, and improve the shortcomings of uneven surface temperature distribution from high thermal resistance. Furthermore, adding the ferromagnetic metal powder to PDMS can improve its conductivity and make the mold a high-low surface temperature gap as low as 1.6 °C. Adding nickel powder to the PDMS mold makes the hardness 2.29 times higher than that of pure PDMS and can withstand a pressure of 7 kg cm−2, which is very conducive to hot embossing. This study used a self-designed five-sided cladding iron block base and a PDMS mold with ferromagnetic metal powder for hot embossing. This heating apparatus can quickly raise the PDMS surface temperature and emboss deep V-groove microstructures on the polycarbonate (PC) film; the replication performance can reach more than 97%.

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.

We developed dielectric heating-assisted nanoimprint method for rapid fabrication of ultraflexible nanostructures. Using spin-coating polyvinyl-chloride (PVC) film on the glass slide, the dielectric heating on PVC film helped the pattern transfer from the mold to PVC film in few seconds. Various kinds of nanostructures were successfully made on PVC films with about 20-μm thickness. We demonstrated the applications of ultraflexible metallic nanostructures for bending measurement using surface plasmon resonance (SPR) and surface enhanced Raman scattering (SERS) on the curved surfaces. For measuring bending angles using SPR on capped nanowire arrays, the minimum detection angle was 2.4 × 10−3 degree under 0.02 nm wavelength resolution. For SERS measurement, the nanorod arrays on a curved substrate can increase SERS signals for two times as compared to planar SERS substrate.

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 paper reports a novel hot embossing technique using rapid heating and uniform pressure for replication of microstructures on polymeric substrates. The rapid heating is made possible by a graphene–polymer composite heater that makes use of the exceptional thermal and electrical properties of graphene. The uniform embossing pressure is achieved by using gas as the pressing medium. A heating rate of 14 °C s−1 can be achieved by applying a voltage of 44 V to a heating area of 30 mm × 30 mm. A facility that integrates graphene-based heating and gas-assisted embossing is designed and implemented. Three microstructures, namely, microlens array, V-groove, and microcylinder array, are successfully replicated on three polymeric substrates. The accuracy and uniformity of replication over the area of 50 mm × 50 mm is also confirmed. Furthermore, the thermal cycle time is reduced to less than 30 s. This study proves the great potential of using graphene–polymer composite heaters in gas-assisted micro hot embossing for replication of microstructures for various applications.

Titanium alloys are widely applied in aircraft, nuclear, and military parts because of their high strength-to-density ratio, high toughness, and high corrosion resistance. However, achieving excellent mechanical properties of these alloys relies on appropriate heat-treatment processes. In this research, the prevalent alloy Ti-6Al-4V was used to investigate the optimization process parameters of heat treatment by using the Taguchi method. Hardness after aging and tensile strength (TS) were chosen as quality characteristics. Eight controllable factors were selected, comprising fan, solution temperature, duration time of solution treatment, protective gas, quench delay time, cooling rate, temperature, and duration time of aging treatment. The experiment was performed using orthogonal arrays of L18(21 × 37). The best combination condition of process parameters was obtained after a Taguchi quality analysis. The quality reproducibility was verified to be excellent through confirmation experiments. The results showed that the hardness after aging was higher than HRC 43 ± 0.5, the TS of rod material higher than 169 ksi, and the TS of plate material higher than 157 ksi while using the best heat-treatment condition. The quality characteristics all met the AMS 4965 specifications of quality requirements for alloy Ti-6Al-4V.

Plastic metal (PM) is a highly advanced material with numerous advantages, such as the convenience associated with its shaping and coating, precise pattern definitions, and convenience for recycling, thereby making it an excellent material for soft electronics. PM material has the ability to be plastically molded into arbitrary deformation by external forces, but it can remain intact even under large deformations as long as PM is encapsulated in polydimethylsiloxane (PDMS). This study aims to verify the feasibility of its application to wearable soft sensors, including flexible and pressure sensors. The experimental results show that with the use of synthetic conditions at a 4:1 mass ratio of liquid metal (LM) to quartz powder, PM yields the best characteristics. Apart from the good electrical conductivity (with a resistivity of 3.29 × 10− 5 Ω-cm), it also has better coating ability, plasticity, and film formability. The developed flexible sensor can sense bending angle changes in the range of 0°–180° with stable performance and with an average gauge factor $${\text{G}}{{\text{F}}_{{\text{avg}}}}$$ of 2.616. With regard to the pressure sensor, when the pressure range is from 0 to 40 psi (≈ 275.79 kPa), the resistance change rate shows a slightly concave-down quadratic curve, while the pressure is greater than 40 psi, the characteristic is a linear relationship with an average slope of 0.022. Furthermore, real-life verification of the two sensors based on experiments shows that their performances are stable and repeatable. Therefore, this study has confirmed that the sensors made of PM can be practically applied to the development of wearable sensors and has emphasized the potential for their use in dynamic sensing applications in humans or robots.

By use of magnetism and magnetic fluid embossing technology, and in combination with the surface microstructure roughness improvement of seal-film, this paper aimed to reach the purpose of magnetic fluid being driven under the magnetic force of an electromagnetic chuck, where the magnetic particles can be evenly scattered and stacked on the surface of the seal-film in order to uniformly lift and convey the microstructure curved surface magnetic embossing force; thus, creating magnetic pressure in the embossing process of a microstructure curved surface. Moreover, during the process, photocuring technology is integrated with the technical features of soft lithography in order to provide more uniform curved surface embossing and photocuring process technology through the combination of fluid and magnetic force. Copyright © 2015 John Wiley & Sons, Ltd.

Components with surface nanostructures suitable for biomimetic dry adhesion have a great potential in applications such as gecko tape, climbing robots, and skin patches. In this study, a nanosphere lithography technique with self-assembly nanospheres was developed to achieve effective and efficient fabrication of dry-adhesion structures. Self-assembled monolayer nanospheres with high regularity were obtained through tilted dip-coating. Reactive-ion etching of the self-assembled nanospheres was used to fabricate nanostructures of different shapes and aspect ratios by varying the etching time. Thereafter, nickel molds with inverse nanostructures were replicated using the electroforming process. Polydimethylsiloxane (PDMS) nanostructures were fabricated through a gas-assisted hot-embossing method. The pulling test was performed to measure the shear adhesion on the glass substrate of a sample, and the static contact angle was measured to verify the hydrophobic property of the structure. The enhancement of the structure indicates that the adhesion force increased from 1.2 to 4.05 N/cm2 and the contact angle increased from 118.6° to 135.2°. This columnar structure can effectively enhance the adhesion ability of PDMS, demonstrating the potential of using nanosphere lithography for the fabrication of adhesive structures.

We develop a simple and competitive fabrication of antireflective (AR) films with high-ordered nanostructure arrays on polycarbonate (PC) substrate by using gas-assisted hot embossing and a self-assembled technique. In this method, a self-assembled monolayer of polystyrene (PS) nanospheres is well-patterned on glass substrates as the first template. Subsequently, we use the plasma sputtering to deposit a conductive layer onto the surface of nanosphere (NS) patterned substrates, and then, electroforming is applied to fabricate a nickel mold with an inverse shape of nanospheres. In the last step, a unique glass transition is utilized to duplicate nanostructures on PC films via gas-assisted hot embossing. Not only in visible light but in near infrared, the optical properties of this AR film are similar or better than for other methods. This fabrication process also has great potential in industry, with its simplicity, large-area but low-cost.

We propose two approaches—hot-embossing and dielectric-heating nanoimprinting methods—for low-cost and rapid fabrication of periodic nanostructures. Each nanofabrication process for the imprinted plastic nanostructures is completed within several seconds without the use of release agents and epoxy. Low-cost, large-area, and highly sensitive aluminum nanostructures on A4 size plastic films are fabricated by evaporating aluminum film on hot-embossing nanostructures. The narrowest bandwidth of the Fano resonance is only 2.7 nm in the visible light region. The periodic aluminum nanostructure achieves a figure of merit of 150, and an intensity sensitivity of 29,345%/RIU (refractive index unit). The rapid fabrication is also achieved by using radio-frequency (RF) sensitive plastic films and a commercial RF welding machine. The dielectric-heating, using RF power, takes advantage of the rapid heating/cooling process and lower electric power consumption. The fabricated capped aluminum nanoslit array has a 5 nm Fano linewidth and 490.46 nm/RIU wavelength sensitivity. The biosensing capabilities of the metallic nanostructures are further verified by measuring antigen–antibody interactions using bovine serum albumin (BSA) and anti-BSA. These rapid and high-throughput fabrication methods can benefit low-cost, highly sensitive biosensors and other sensing applications.

The paper presents the effect of substrates on the characteristics of PbZrxTi1−xO3 (PZT) thin film fabricated by sol-gel spin coating technology. The PZT sol-gel is prepared by mixing PZT powder and PZT solution, and fabricated on various substrates, including copper (Cu), alumina (Al2O3), stainless steel (SS) and titanium (Ti). The dielectric characteristics and orientation of films had been measured by SEM, LCR meter, XRD for comparison. The experimental results indicate that the substrates having the similar characteristics with PZT film would result in better crystallization, charge storage capacity and energy transfer efficiency of film.

In recent years, many replication methods of microstructures on large-area substrates have been reported. The plate-to-plate hot embossing process is a low cost, fast, high throughput and the most possibility of mass production method for replication of micro/nano structures with high precision and high quality. However, micro hot embossing is not practical to use in mass production due to the many difficulties. This paper reports a innovative non-uniform heating hot embossing system for fabrication of large-size, high precise and high brightness light guide plate. Steam is used as heating medium, and water of 12°C is used for cooling. The v-groove patterns in the stamper have been replicated to the light guide plates (LGPs) with an area of 488 mm by 277 mm. The experimental results show that the non-uniform heating system could achieve a transcription rate of over 99%, compared with 95% using conventional uniform heating system. Furthermore, less warpage, the less thickness variation, the higher average luminance and the higher brightness field distribution have been found. The results indicate that non-uniform heating system is likely to be a promising technique for the fabrication of optical elements.

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 study proposed a new imprinting process using electromagnetic-field- assisted imprinting technology, a composite PDMS magnetic soft mold, and UV-LED arrays photocuring equipment to change an even microlens mold by imprinting the replication into a gradient microlens structure. This function is similar to the continuous gray scale technology of the semi-conductor industry. However, the structural appearance, as defined by the gray scale photo mask process, is smoother and continuous. As the method only requires one time of imprinting, the process is simple, with lower cost and higher competitiveness, thus providing a more effective alternative for imprinting technology and applications. This study used pressure-sensitive film to explore the imprinting pressure distribution of gradient magnetic soft molding. The imprinting results showed that, magnetic powder is distributed in a linear tilting pattern that is consistent with pressure measurement distribution. Hence, the magnetic powder casting angle control of a precision tilt platform can achieve gradient control of imprinting pressure. Finally, the observations and analysis by instruments, including SEM, a surface profiler, and a Laser Scanning Confocal Microscope, confirmed that the gradient magnetic PDMS film made using a precision tilt platform to control the magnetic powder casting angle, coupled with electromagnetic-field-assisted imprinting and UV-LED arrays light curing technology, can replicate the gradient microlens arrays structure of the same tilt angle through one imprinting.

Nanostructure-based sensors are capable of sensitive and label-free detection for biomedical applications. However, high-throughput and low-cost fabrication techniques are the main issues which should be addressed. In this study, chip-based nanostructures for intensity-sensitive detection were fabricated and tested using a thermal-annealing-assisted template-stripping method. Large-area uniform nanoslit arrays with a 500 nm period and various slit widths, from 30 to 165 nm, were made on plastic films. A transverse magnetic-polarized wave in these gold nanostructures generated sharp and asymmetric Fano resonances in transmission spectra. The full width at half-maximum bandwidth decreased with the decrease of the slit width. The narrowest bandwidth was smaller than 10 nm. Compared to nanoslit arrays on glass substrates using electron-beam lithography, the proposed chip has a higher intensity sensitivity up to 10367%/RIU (refractive index unit) and reaches a figure of merit up to 55. The higher intensity sensitivity for the template-stripped nanostructure is attributed to a smoother gold surface and larger grain sizes on the plastic film, which reduces the surface plasmon propagation loss.

Poly-methyl methacrylate (PMMA) has been widely used for optical and microfluidic devices. This paper is devoted to the development of an effective low-temperature PMMA bonding technology. For bonding, Carbon dioxide (CO2) has been used as gas solvent and pressuring agent. The bonding temperature thus is lowered and the pressing pressure becomes uniform. An innovative two-stage CO2-assisted thermal fusion bonding process has been developed which takes the soaking and releasing times of CO2 into account. The experimental results show that this new process significantly enhances the flatness after bonding process and increases bonding area and bonding strength. By coating a layer of PMMA solution on bonding surface, the diffusion number of chain increases, and thus further increases the bonding strength.

Periodic nanostructures have played critical roles in key components for optical applications. Femtosecond laser-induced periodic surface structures (FLIPSS) in nano scale on many material surfaces have drawn much attention in recent years. However, the relatively low throughput of the direct inducing process limits its potential in regard to high volume manufacturing. In this study, fast replication of FLIPSS on Polycarbonate (PC) films by gas-assisted a hot embossing process is demonstrated. A selected surface area of a stainless steel thin plate is irradiated by femtosecond laser pulses to form a kind of periodic anti-reflective nanostructure with a period measuring 600–700 nm. The stainless plate was then used as a template for the hot embossing process. PC films with periodic nanostructures are then replicated quickly. Compared to the original PC film, at least up to 5% of the reflectivity of the fabricated PC films with nanostructures was reduced. It proves that the gas-assisted hot embossing could procure uniform transcription for anti-reflection PC film with stainless steel template that is irradiated by femtosecond laser pulses.

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 paper reports a novel and effective method for the fabrication of gold sub-wavelength pore array using gas-assisted hot embossing. The novel fabrication comprises the fabrication of AAO template with high order pore array, sputter-coating of gold and gas-assisted hot embossing. AAO template is fabricated by a two-step anodization process. It is then coated with gold (100nm thick). The gold sub-wavelength pore array is finally formed by using gas-assisted hot embossing process. The transmission spectra of gold sub-wavelength pore array are measured in several conditions such as air, water and glycerol/water mixture. The detection shows significant shift in the wavelength of resonance peak. The gold sub-wavelength pore array can be employed as optical biosensors.

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 study reports an effective process for low temperature replication of polymeric microlens array using carbon dioxide (CO"2) as softening solvent and then as embossing pressure. Supercritical CO"2 is employed to soften the surface of polymer substrate and then apply pressure on it. Accordingly, microlens can be formed on the polymer substrate at low temperature. Using gas as embossing pressure can provide uniform pressure for large-area replication. During the embossing process, an array of convex microlenses is generated by partial protrusion of the substrate into the micro-holes of the mold under the action of embossing pressure and surface tension. The uniformity of large-area fabrication and optical property of the fabricated refractive microlens array on a 260mmx110mm poly (methyl methacrylate) (PMMA) substrate have been verified. Little residual stress can be observed by polariscope. With the proposed method, the large-area embossing can be performed without heating and cooling. Moreover, the problems of non-uniform pressure and residual stress can be overcome.

In recent years, roller imprinting has been considered as the most efficient technique for replicating microstructures onto polymeric substrate. However, the preparation of roller is still a challenge. This paper reports an effective method of directly fabricating microstructures on metal rollers; the process includes dip coating of the photoresist on the roller, stepped rotating lithography and electroless nickel plating. The facilities for dip coating and stepped rotating lithography have been implemented. The positive photoresist (EPG510) is first uniformly coated on the roller surface using dip coating process. The microstructures on the roller can be then defined by using stepped rotating photolithography with a glass mask, followed by electroless nickel plating. Rigid microstructured roller can be obtained. The experimental results show that the dip-coated film thickness on the roller increases with the withdrawal velocity of the roller from the resin bath. The coated photoresist on the roller surface is uniform. The microstructures have been successfully fabricated onto the metal roller using the stepped rotating lithography; the rigid nickel microstructures with various pitches on metal roller can be fabricated by adjusting the rotating degree of stepped rotating lithography.

This study employed the Anodic Aluminum Oxide (AAO) method twice for AAO processing to prepare neatly-arranged aluminum oxide film micro nano porous structure, and conducted experiments by adjusting different condition parameters (current, voltage, and temperature). The experimental results showed that voltage would directly affect the pore space and surface roughness of the aluminum oxide film. In addition, after anodic treatment, the positive and negative surfaces demonstrated varying degrees of roughness under the same conditions. In this study, the experiment of surface roughness impact on cell proliferation demonstrated that cell proliferation was better when surface roughness was in the range of 0.4 nm < Ra < 1.2 nm.

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.

Traditionally, making light-blocking micro-lens arrays requires not only precise positioning, but also a lot of time and cost. In this study, we try to utilize some innovative technologies. New molds are based on stainless steel plates penetrated by micro-aperture arrays. Together with gas-assisted nanoparticle fluid magnetic imprinting technology, a semi-sphere lens can be shaped by utilizing the properties of surface tension of the plastic film. It can be used to produce the plastic micro-lens array that is capable of light-blocking directly as projection lens. Using optical diffusion film, Fresnel lens, and single mask in centimeter level, we can construct a projection lithography system with micro-lens array. This brand new process technology simplifies the manufacture of micro-lens array with light-blocking capability to just one step. It cuts required time significantly and reduces the cost and pollution remarkably. Finally, we successfully generated some micrometer level pattern arrays on the photo...

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.

A transfer stamping process is proposed to fabricate micro-scale organic flexible electrodes. With different adhesion forces of the transferring interfaces, ink/mold and ink/substrate, patterns are formed from the relief features of the elastomeric mold to the substrate without residual layer, and no complex pre-process and steps are needed. To estimate the deformation during pressing, the sagging height of the mold is analyzed with finite element method (FEM). Two conductive polymers, PEDOT:PSS and silver paste, are transferred from the flat relief features of the mold to the PET substrate. The coating characteristics and problems are discussed. The transfer stamping process is also employed to fabricate electrodes on the dielectric/ITO film and to form an organic flexible capacitance. This paper demonstrates the potential of transfer stamping in fabricating organic electronic components, such as organic integrated circuit, OLED and OTFT.

In this study, we look into an innovative technology that utilizes nanoparticles as a medium for imprinting. This technology integrates the advantages of soft lithography, photo-cure resist, and gas assisted imprinting. We try to produce ridge waveguides and microlens arrays by gas-assisted nanoparticle-based soft mould imprinting on photo-cure resists. It helps the application and technology of nano-imprinting becoming more sophisticated. We find that PDMS can be used to precisely replicate micro-to-nanometer level microstructures. Together with nanoparticles and well-proportioned gas pressure, we can construct a perfect shape of microstructures and achieve a conformal contact with the surface of base material. It increases the effective imprinting area significantly and improves the replication capability of the transfer. Meanwhile, the PDMS soft mould is easy for production and fast in replication, which reduces the cost remarkably. Furthermore, it has a low surface free energy and low viscosity to the...

In this study, we try to discuss the formation defects found in the application of air-assisted soft mold UV-cured nano imprint lithography technology in the manufacture of optical waveguide devices, and find a solution. Meanwhile, we try to utilize the nano-indentation technology in the material quality detection for optical waveguide devices. The results tell us that there is a corresponding relationship between the indentation hardness and procedure parameters under nano-meter level depth. For example, the indentation tends to be harder when it is lowly loaded and shallow in depth. Closer it gets to the edge of waveguide's turning, lower the indentation hardness will be. At the same time, different exposal process results in different structural intensity. Therefore, the high structural intensity without forming defects of optical waveguide with less optical loss and better optical transmission. Copyright © 2008 John Wiley & Sons, Ltd.

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.