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This research reports the development of anti-reflective films for solar cell application by employing the hot embossing technique with laser-patterned microstructures. The goal is to increase the light-trapping ability of crystalline silicon (c-Si) wafers by employing micro-textured polycarbonate films to decrease surface reflectance. A series of micron-sized rhombus patterns were first created on the titanium-grade-5 mold using a fiber laser, and then, polycarbonate sheets were hot embossed under the optimized conditions. In order to investigate the influence of the embossing temperature, pressure, and time on the average reflectance and surface roughness of the films, a parametric analysis was carried out through the Taguchi method. The most effective embossing parameters were the embossing temperature of $220^{\circ }$C, pressure of 50 kg/cm², and an 8 min embossing duration, which resulted in a significant decrease of 41.53% reflectivity. The findings in the existing study and a fuzzy logic-based multi-objective optimization approach also supported these findings, suggesting the scalability and efficiency of the process. It is evident that the proposed method could provide a more significant cost reduction in fabricating anti-reflective films with large-area applications to optoelectronics devices such as solar cells, LEDs, and optical sensors. This study opens the door to further studies about using micro-patterned films to enhance light management for other energy-efficient devices.

A simple method for the fabrication of polymer master for antireflective surface is presented. In conventional fabrication methods for antireflective surface, coating method with low refractive index have usually been used. However, it is required to have a high cost and a long processing time for mass production. In this paper, antireflective surface was fabricated by using hot embossing process with porous anodized aluminum oxide. Through multi-AAO and etching processes, nano patterned master with high aspect ratio was fabricated at the large area. Size and aspect ratio of nano patterned master are about 175 ± 25nm and 2 ~ 3, respectively. In order to replicate nano patterned master, hot embossing process was performed by varying the processing parameters such as temperature, pressure and embossing time etc. Finally, antireflective surface can be successfully obtained after etching process to remove selectively silicon layer of AAO master. Optical and rheological characteristics of antireflective surface were analyzed by using SEM, EDX and spectrometer inspection. Antireflective structure by replicating hot embossing process can be applied to various displays and automobile components.

Glass hot-embossing is one of essential techniques for the development of high-performance optical, bio, and chemical micro electromechanical system (MEMS) devices. This method is convenient, does not require routine access to clean rooms and photolithographic equipment, and can be used to produce multiple copies of a quartz mold as well as a MEMS component. In this study, quartz molds were prepared by hot-embossing with the glassy carbon (GC) masters, and they were applied to the hot-emboss of borosilicate glasses. The GC masters were prepared by dicing and focused ion beam (FIB) milling techniques. Additionally, the surfaces of the embossed quartz molds were coated with molybdenum barrier layers before embossing borosilicate glasses. As a result, micro-hot-embossed structures could be developed in borosilicate glasses with high fidelity by hot embossing with quartz molds.

Proper bonding technique is investigated to achieve leakage-free surface-driven capillary flow in polymethylmethacrylate (PMMA) microfluidic devices. SU-8-based silicon stamp is fabricated by maskless lithography. This stamp is used to produce PMMA microchannel structure by hot embossing lithography. A direct bonding technique is mainly employed for leakage-free sealing inside PMMA microfluidic devices. The effect of surface wettability on surface-driven capillary flow is also investigated in PMMA microfluidic devices. The separation of polystyrene microparticles in PMMA laboratory-on-a-chip systems is investigated with the reduction of separation time by air dielectric barrier discharge (DBD) plasma processing of channel surfaces. This study is useful to fabricate the microfluidic laboratory-on-a-chip systems and to understand the surface-driven capillary flow.

In this research paper, in total 212 individual leakage-free Polymethylmethacrylate (PMMA) microfluidic devices are fabricated by maskless lithography, hot embossing lithography and direct bonding technique. The effect of channel aspect ratio on dyed water flow is investigated using these microfluidic devices. Experimental studies show that the dyed water flow is faster on the surface of higher wettability. The effect of capillary pressure on dyed water flow is studied in the fabricated PMMA microfluidic devices. According to the experimental observations, the centrifugal force has prominent effect on the dyed water flow. Also, the effect of bend angle is investigated on the surface-driven capillary flow of water. The polystyrene microparticles have been separated in the microfluidic lab-on-a-chip systems using the investigated flow features. A 100% separation efficiency is achieved in these lab-on-a-chip systems. These microfluidic lab-on-a-chip systems can be used to separate blood cells from human whole blood for further clinical tests. These experimental studies are important in bioengineering applications. The effect of bend angle as channel geometry to control the surface-driven capillary flow is investigated as a novel approach to control the separation time in microfluidic lab-on-a-chip systems. Also, the effect of surface wettability as surface property to control the surface-driven capillary flow is investigated as a novel approach to control the separation time in microfluidic lab-on-a-chip systems.

A simple and low-cost fabrication method of polymeric optical waveguides with large core sizes for plastic optical fibers is presented. The waveguides are fabricated by hot embossing with a rectangular ridge ultraviolet (UV)-cured epoxy resin stamper. The stamper is fabricated by replication of a rectangular groove mold that is made from silicone rubber replicated from a rectangular ridge original master made from thick photoresist (SU-8). A rectangular ridge shape of the original photoresist master of 1 mm size was realized by using a flattening process, which involves hot embossing before the exposure process and using a UV-cut filter during the exposure process.

We fabricated polymer thin films with two-dimensional periodic nanopatterns using an imprinting technique with the hot embossing process. The silicon stamp employed in the imprinting has a triangular array of circular rods. The period of the array is 410 nm, and the radius and the height of a rod are 100 nm and 150 nm, respectively. The imprinting in the polymer film results in holes with the average radius of 105 nm and the average depth of 130 nm, which are close to the dimension of the stamp. The results show that the thermal imprinting process can be suitable for the implementation of nanopatterned polymer thin films. The interesting optical properties of the nanopatterned polymer thin films are also discussed.

Since 1985, the polymerse chain reaction (PCR) became very popular among the field of molecular biology. It is very powerful for amplification DNA segment and it had a variety of applications in medicinal, virus, disease, and monitoring. In this study, a simple and miniature PCR chip will be presented with an external peristaltic pump utilized to driving liquid into PCR chip.¹ The PCR chip was made of PMMA (Polymethylmethacrylate) and glass. The hot embossing technique was used to fabricate the micro channel on the PMMA. The copper was sputtered on the glass as the heater. The glass and PMMA were bonded by PDMS. In typically, heater temperature was 94°C for denature, 55°C for annealing, 72°C for extension. Therefore, the heaters formed three different zones of temperature along the channel that the length ration on each temperature zone was 1:1:2 for denature, annealing and extension, respectively.^2,3 For temperature control, the PID control mode was used to regulate the temperature on reaction and the DC power was as the power supplier. The thermal sensors were adhered on the heater beside the channel.

Hot embossing is a well-acknowledged low cost, high resolution, large area 3D patterning process for polymers. This technique allows rapid prototyping for high volume production of fully patterned substrates for a wide range of thermoplastic polymer materials. The advantages of using polymer substrates over common Micro-Electro-Mechanical System (MEMS) processing materials like glass, silicon or quartz are: bio-compatible surfaces, easy manufacturability, low cost for high volume production, suitable for use in micro- and nano-fabrication, low conductivity, wide range of optical properties just to name a few. The article will present experimental results on HE processes with PMMA, mr-I8030, mr-L6000 and NEB22 on full 8" wafer sizes. Packaging of the imprinted features is a key technology for a wide variety of optical and fluidic applications in the μm and nm-range: m-TAS, micro-mixers, micro-reactors, electrophoresis cells, switches, data storage, etc. Most packaging techniques employed today, use glue material or high temperature sintering methods to bond structured polymer wafers together. These techniques are influencing the appearance of the sub-micron structures. A promising low-temperature polymer-to-polymer direct bonding technique utilizing the cleaning and surface activating behavior of plasma should be established here.

Research and development activities at the Institute for Microstructure Technology (IMT) of Forschungszentrum Karlsruhe, Germany (FZK) are focused on microsystem technologies with polymers. The strategic areas for applications are in micro-optics and micro-fluidics. Microfabrication processes are developed for manufacturing prototypes or for producing micro-components and microsystems in small volume for customers. Finally, production technologies can also be transferred to industries. Two core fabrication technologies have been established at IMT: LIGA that was invented and developed at FZK is currently used predominantly for applications in micro-optics as well as advanced research projects. The second technology, AMANDA, serves for fabricating polymer micro-fluidic components and systems.

The paper deals with the development of silicon tools and an appropriate hot embossing technology for polymers. With this technology, high quality embossing of optical or fluidic structure for high precision requirements in a batch process is possible thereby reducing system costs. Possible usage is the production of Micro Electro Mechanical Systems (MEMS) for optical or fluidic applications. This could be sensors for chemical analysis of liquids or BioMEMS. Further promising applications are multifunctional printed circuit boards (PCB) or micro cooler. Up to now for coarser dimensions the use of conventional made (e.g. miling) steel tools is common. For forming of smallest structures down to the sub-micrometer range with excellent surface roughness LIGA technology is applied. However, in order to reduce the system costs LIGA tools shall be substituted by silicon tools. Deep reactive ion etching (DRIE) is used to fabricate such an embossing tools allowing complex geometrical figures. For fluidics or optical applications the tool structures have to show a tapered (positive) profile and sufficient low roughness. Roughness can be minimised by further oxidation and etch steps. The hot embossing experiments which will be presented show the capability of the optimised DRIE technology for the aimed application field.

MEMS (Micro Electro Mechanical Systems) products are being spread from laboratory to industries. But Silicon-based MEMS products are usually expensive and not suitable for low cost production. Hence, there is an emerging need in terms of cost effectiveness to transfer MEMS from silicon-based materials to other materials, such as glasses and polymers. Micro hot embossing is expected to be a novel technique for producing MEMS components/products with low cost, and will potentially find wide applications in micro fluidics, biomedical and micro optical areas. In this paper, a hot embossing instrument is illustrated and is used for the process development of micro/nano structure forming with polycarbonate (PC) and Polyetheretherketone (PEEK) by using the Nickel mold. Fabrications of micro vertical reflecting mirrors and cantilevers for an 8×8 optical switch have been carried out, replication of micro grooves and pyramid cavities with nanometer precision for passive alignment of optical fibers and micro ball lenses have been performed as well. The results show that hot embossing is a promising technology for cost effective micro/nano fabrications of MEMS.

This paper presents an 8×8 optical switch consisting of a micro cantilever array. Each cantilever, with a vertical micro mirror located on one end of it, was driven by electrostatic actuation. The optical switch was fabricated using combined silicon process, electroplating and hot embossing. The optical switch, embossed with a polymer material, was aligned and assembled together with input and output optical fibers via grooves etched on a silicon substrate. Considering the fabrication process and material used, this optical switch is suitable for cost-effective mass production, and will potentially find wide applications for fiber-to-the-home communications.

A simple method for the fabrication of polymer master for antireflective surface is presented. In conventional fabrication methods for antireflective surface, coating method with low refractive index have usually been used. However, it is required to have a high cost and a long processing time for mass production. In this paper, antireflective surface was fabricated by using hot embossing process with porous anodized aluminum oxide. Through multi-AAO and etching processes, nano patterned master with high aspect ratio was fabricated at the large area. Size and aspect ratio of nano patterned master are about 175 ± 25nm and 2~3, respectively. In order to replicate nano patterned master, hot embossing process was performed by varying the processing parameters such as temperature, pressure and embossing time etc. Finally, antireflective surface can be successfully obtained after etching process to remove selectively silicon layer of AAO master. Optical and rheological characteristics of antireflective surface were analyzed by using SEM, EDX and spectrometer inspection. Antireflective structure by replicating hot embossing process can be applied to various displays and automobile components.

Glass hot-embossing is one of essential techniques for the development of high-performance optical, bio, and chemical micro electromechanical system (MEMS) devices. This method is convenient, does not require routine access to clean rooms and photolithographic equipment, and can be used to produce multiple copies of a quartz mold as well as a MEMS component. In this study, quartz molds were prepared by hot-embossing with the glassy carbon (GC) masters, and they were applied to the hot-emboss of borosilicate glasses. The GC masters were prepared by dicing and focused ion beam (FIB) milling techniques. Additionally, the surfaces of the embossed quartz molds were coated with molybdenum barrier layers before embossing borosilicate glasses. As a result, micro-hot-embossed structures could be developed in borosilicate glasses with high fidelity by hot embossing with quartz molds.