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Studies of Polymer Deformation and Recovery in Hot Embossing  [PDF]
X. C. Shan,Y. C. Liu,H. J. Lu,Z. F. Wang,Y. C. Lam
Computer Science , 2008,
Abstract: In large area micro hot embossing, the process temperature plays a critical role to both the local fidelity of microstructure formation and global uniformity. The significance of low temperature hot embossing is to improve global flatness of embossed devices. This paper reports on experimental studies of polymer deformation and relaxation in micro embossing when the process temperatures are below or near its glass transition temperature (Tg). In this investigation, an indentation system and a micro embosser were used to investigate the relationship of microstructure formation versus process temperature and load pressure. The depth of indentation was controlled and the load force at a certain indentation depth was measured. Experiments were carried out using 1 mm thick PMMA films with the process temperature ranging from Tg-55 degrees C to Tg +20 degrees C. The embossed structures included a single micro cavity and groups of micro cavity arrays. It was found that at temperature of Tg-55 degrees C, elastic deformation dominated the formation of microstructures and significant relaxation happened after embossing. From Tg-20 degrees C to Tg, plastic deformation dominated polymer deformation, and permanent cavities could be formed on PMMA substrates without obvious relaxation. However, the formation of protrusive structures as micro pillars was not complete since there was little polymer flow. With an increase in process temperature, microstructure could be formed under lower loading pressure. Considering the fidelity of a single microstructure and global flatness of embossed substrates, micro hot embossing at a low process temperature, but with good fidelity, should be preferred.
Study of Double-Side Ultrasonic Embossing for Fabrication of Microstructures on Thermoplastic Polymer Substrates  [PDF]
Yi Luo, Xu Yan, Na Qi, Xiaodong Wang, Liangjiang Wang
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0061647
Abstract: Double-side replication of polymer substrates is beneficial to the design and the fabrication of 3-demensional devices. The ultrasonic embossing method is a promising, high efficiency and low cost replication method for thermoplastic substrates. It is convenient to apply silicon molds in ultrasonic embossing, because microstructures can be easily fabricated on silicon wafers with etching techniques. To reduce the risk of damaging to silicon molds and to improve the replication uniformity on both sides of the polymer substrates, thermal assisted ultrasonic embossing method was proposed and tested. The processing parameters for the replication of polymethyl methacrylate (PMMA), including ultrasonic amplitude, ultrasonic force, ultrasonic time, and thermal assisted temperature were studied using orthogonal array experiments. The influences of the substrate thickness, pattern style and density were also investigated. The experiment results show that the principal parameters for the upper and lower surface replication are ultrasonic amplitude and thermal assisted temperature, respectively. As to the replication uniformity on both sides, the ultrasonic force has the maximal influence. Using the optimized parameters, the replication rate reached 97.5% on both sides of the PMMA substrate, and the cycle time was less than 50 s.
Ultrasonic Hot Embossing  [PDF]
Werner Karl Schomburg,Katharina Burlage,Christof Gerhardy
Micromachines , 2011, DOI: 10.3390/mi2020157
Abstract: Ultrasonic hot embossing is a new process for fast and low-cost production of micro systems from polymer. Investment costs are on the order of 20.000 € and cycle times are a few seconds. Microstructures are fabricated on polymer foils and can be combined to three-dimensional systems by ultrasonic welding.
A Novel Extrusion Microns Embossing Method of Polymer Film  [PDF]
Ying Liu, Wenlong Liu, Yajun Zhang, Daming Wu, Xinliang Wang
Modern Mechanical Engineering (MME) , 2012, DOI: 10.4236/mme.2012.22005
Abstract: A continuous hot embossing method is reported in this paper. The continuous means that the extruder and the hot embossing equipment is used in series, the polymer film is embossed after extrusion immediately. The basic principle of this method, the key design point and the corresponding operate process of the embossing equipment is described in this paper. The polymer diffuser with micro-lens matrix on its surface is designed and the optical properties are simulated. Then, the diffuser is fabricated by the embossing equipment. The optical properties of the diffuser are tested and compared with the results of the simulation to verify the reproducibility of the equipment. By this method, the diffuser with large area can be fabricated with high precision of graphic replication, high efficiency and low cost.
Hot Roller Embossing for the Creation of Microfluidic Devices  [PDF]
Sum Huan Ng,Zhenfeng Wang
Computer Science , 2008,
Abstract: We report on the hot roller embossing of polymer sheets for the creation of microfluidic structures. Measurements conducted on 100 $\mu$m features showed that the lateral dimensions could be replicated to within 2% tolerance, while over 85% of mould depth was embossed. Feature sizes down to 50 $\mu$m and feature depths up to 30 $\mu$m had been achieved. At lower temperatures, asymmetric pile up of polymer material outside embossed regions was observed with higher pile up occurring on the trailing side of the embossed regions.
Modeling of large area hot embossing  [PDF]
M. Worgull,K. K. Kabanemi,J. -P. Marcotte,J. -F. Hétu,M. Heckele
Computer Science , 2008,
Abstract: Today, hot embossing and injection molding belong to the established plastic molding processes in microengineering. Based on experimental findings, a variety of microstructures have been replicated so far using the processes. However, with increasing requirements regarding the embossing surface and the simultaneous decrease of the structure size down into the nanorange, increasing know-how is needed to adapt hot embossing to industrial standards. To reach this objective, a German-Canadian cooperation project has been launched to study hot embossing theoretically by a process simulation and experimentally. The present publication shall report about the first results of the simulation - the modeling and simulation of large area replication based on an eight inch microstructured mold.
Fabrication of flexible UV nanoimprint mold with fluorinated polymer-coated PET film  [cached]
Shin Ju-Hyeon,Lee Seong-Hwan,Byeon Kyeong-Jae,Han Kang-Soo
Nanoscale Research Letters , 2011,
Abstract: UV curing nanoimprint lithography is one of the most promising techniques for the fabrication of micro- to nano-sized patterns on various substrates with high throughput and a low production cost. The UV nanoimprint process requires a transparent template with micro- to nano-sized surface protrusions, having a low surface energy and good flexibility. Therefore, the development of low-cost, transparent, and flexible templates is essential. In this study, a flexible polyethylene terephthalate (PET) film coated with a fluorinated polymer material was used as an imprinting mold. Micro- and nano-sized surface protrusion patterns were formed on the fluorinated polymer layer by the hot embossing process from a Si master template. Then, the replicated pattern of the fluorinated polymer, coated on the flexible PET film, was used as a template for the UV nanoimprint process without any anti-stiction coating process. In this way, the micro- to nano-sized patterns of the original master Si template were replicated on various substrates, including a flat Si substrate and curved acryl substrate, with high fidelity using UV nanoimprint lithography.
Fabrication of Biochips with Micro Fluidic Channels by Micro End-milling and Powder Blasting  [PDF]
Dae Jin Yun,Tae Il Seo,Dong Sam Park
Sensors , 2008, DOI: 10.3390/s8021308
Abstract: For microfabrications of biochips with micro fluidic channels, a large number of microfabrication techniques based on silicon or glass-based Micro-Electro-Mechanical System (MEMS) technologies were proposed in the last decade. In recent years, for low cost and mass production, polymer-based microfabrication techniques by microinjection molding and micro hot embossing have been proposed. These techniques, which require a proper photoresist, mask, UV light exposure, developing, and electroplating as a preprocess, are considered to have some problems. In this study, we propose a new microfabrication technology which consists of micro end-milling and powder blasting. This technique could be directly applied to fabricate the metal mold without any preprocesses. The metal mold with micro-channels is machined by micro end-milling, and then, burrs generated in the end-milling process are removed by powder blasting. From the experimental results, micro end-milling combined with powder blasting could be applied effectively for fabrication of the injection mold of biochips with micro fluidic channels.
Fabrication of Biochips with Micro Fluidic Channels by Micro End-milling and Powder Blasting
Dae Jin Yun,Tae Il Seo,Dong Sam Park
Sensors , 2008,
Abstract: For microfabrications of biochips with micro fluidic channels, a large number of microfabrication techniques based on silicon or glass-based Micro-Electro-Mechanical System (MEMS) technologies were proposed in the last decade. In recent years, for low cost and mass production, polymer-based microfabrication techniques by microinjection molding and micro hot embossing have been proposed. These techniques, which require a proper photoresist, mask, UV light exposure, developing, and electroplating as a preprocess, are considered to have some problems. In this study, we propose a new microfabrication technology which consists of micro end-milling and powder blasting. This technique could be directly applied to fabricate the metal mold without any preprocesses. The metal mold with micro-channels is machined by micro end-milling, and then, burrs generated in the end-milling process are removed by powder blasting. From the experimental results, micro end-milling combined with powder blasting could be applied effectively for fabrication of the injection mold of biochips with micro fluidic channels.
Determination of an Innovative Consistent Law for the Rheological Behavior of Polymer/Carbon Nanotubes Composites  [PDF]
F. Thiébaud
Soft Nanoscience Letters (SNL) , 2011, DOI: 10.4236/snl.2011.11001
Abstract: An innovative constitutive model for the rheological behavior of the polymer/carbon nanotubes composites is proposed in this paper. Based on experimental investigations, this consistent law gives the evolution of the composite shear viscosity versus the shear rate, over a large range, and the temperature with various carbon nanotubes mass fractions. Hence, this consistent could be implemented in a finite element code in order to lead many polymer/carbon nanotubes manufacturing process like injection molding or hot embossing.
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