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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.

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.

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.

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.

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.

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.

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.

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.

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 reports three innovative methods of rapid heating and uniform pressing for micro hot embossing. Fluids were used as heating and pressing media. With these three systems, the temperature of substrate rises rapidly and uniform pressure is exerted over the whole substrate. The working fluids used in this experiment included steam, gas, and oil. In addition, rapid heating through far infrared radiation (FIR) was also implemented with a gas pressurized hot embossing process. It was found that a 0.2 millimeter-thick PVC substrate can be heated from 25°C to 130°C in 30 seconds using steam heating, in only 25 seconds using FIR heating, and in 3.5 minutes using oil heating. The heating speeds of all three methods are much faster than those using conventional hot-plate heating, which takes more than 10 minutes. Successful replications of micro-features onto substrates have been achieved.

Hot embossing has proven productive for the parallel replication of precision micro-features onto thermoplastic substrates at low cost. During conventional hot embossing, the substrate and the stamp are brought into contact and are compressed directly by the hot plates of the machine. The accuracy and area of replication are limited due to the inherent non-uniform pressure distribution. Si-wafers are too brittle to be used as embossing tools with the conventional hot embossing operation. This paper describes an innovative pressurizing method for hot embossing using gas as pressure media. The film/stamper/substrate stack is placed in a closed chamber. After heating, the gas is blown in at high pressure to pressurize the stack. Micro patterns in the stamp can be successfully replicated onto the substrate. Perfectly uniform embossing pressure throughout the whole area can be achieved. Glass or wafers with micro-features on their surfaces can be used as stampers directly.