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Nanotechnology for Tissue Engineering and Regenerative Medicine
Published in Šeila Selimovic, Nanopatterning and Nanoscale Devices for Biological Applications, 2017
Şükran Şeker, Y. Emre Arslan, Serap Durkut, A. Eser Elçin, Y. Murat Elçin
Replica molding [91] includes the transfer of a pattern from a rigid or elastomeric mold into another material by solidifying a liquid polymer precursor against a topo-graphically patterned mold to fabricate objects with a specific topography. Replica molding can be further divided into subgroups: microtransfer molding, micromolding in capillaries, and ultraviolet (UV) molding. Embossing can be defined as a process that involves imprinting a pattern onto an initially flat surface by pressing a mold into the surface. This technique can generally be divided into two subgroups based on the master type used: nanoimprinting (uses a rigid master) and solvent-assisted micro-molding (uses a soft mold as the master). There are differences between the replica molding and embossing techniques. The mold is a solid film in embossing, while in replica molding it is a liquid precursor [90]. Printing includes material transfer from the mold onto the substrate. This technique can be further divided into the subgroups of microcontact printing and nanotransfer printing (Figure 14.12).
Plastic Optics
Published in Anees Ahmad, Handbook of Optomechanical Engineering, 2017
Embossing consists of generating features into a substrate by pressing a master form into it. There are two general types of embossing, roller based and stamper based. Roller-based embossing is a continuous process, where a roll of plastic film is unwound and passed between a pair of rollers, which imprint a pattern onto the film. The film is then typically wound back into a roll. The pattern is imparted onto the film through the use of the pressure of the rollers. The film may be heated to soften it before it reaches the rollers, then cools to affix the pattern that has been embossed. A variant of pressure roller embossing is UV embossing. In this case, a layer of UV curable liquid is applied to the plastic film by the roller. The film is then exposed to UV light, which cures the liquid layer, affixing the pattern applied by the roller.
LIGA and Micromolding
Published in Mohamed Gad-el-Hak, MEMS, 2005
Replication of micro- and nano-size structures has been successfully achieved using hot embossing [Becker and Dietz, 1998; Kopp et al., 1997; Chou et al., 1996; Schift et al., 1999; Jaszewski et al., 1998; Casey et al., 1997; Gottschalch et al., 1999]. Adding an antiadhesive film to reduce the interaction between the mold and the replica during embossing has also been studied [Jaszewski et al., 1997; Jaszewski et al., 1999]. Instead of the conventional nickel molds, the possibility of using silicon molds has been demonstrated due to its excellent surface quality and easy mold release [Becker and Heim, 1999; Lin et al., 1996]. Also, the use of a plastic mold in the embossing process was recently illustrated [Casey et al., 1999]. In our own efforts [Lee et al., 1999; Juang et al., 2000], we used a cyclic process in a 30-ton Wabash press to fabricate a CD-based fluidic platform (see Figure 4.48). We have worked with optical quality PC (OQPC) (GE Plastics, Lexan Tg = 135°C) and regular PC (GE Plastics, Lexan, Tg = 145°C). The variables explored involve the compression force (from 2 to 25 tons) and the embossing and deembossing temperature. In Figure 4.48, we plot the depths of replicated channels in PC vs. the applied force. The smallest channels can be replicated at a relatively low force and temperature. For the deeper channels, a higher temperature and larger force must be used. This means a longer cycle time and a larger residual stress. That is why embossing is good for small structures and low aspect ratios but difficult for large structures and features. For 3-D structures (e.g., channels with different depth), the embossing pressure can be very high. Correspondingly, the molded-in stresses are also very large (see Figure 4.43).
Finite element analysis of ultrasonic vibration-assisted microstructure hot glass embossing process
Published in Australian Journal of Mechanical Engineering, 2019
LanPhuong Nguyen, Ming-Hui Wu, Chinghua Hung
Nowadays, Field Emission Displays (FED) have been widely used in television, computers as well as in laboratories and medical applications. Figure 1 shows the three parts of the FED screen (http://escience.anu.edu.au/lecture/cg/Display/FED.en.html). Microtips, so-called electron guns, are on the cathode, which emit electrons. In order to manufacture these microstructures, lithography etching technology and micro-machining technology have been applied. However, these methods are usually complex and high cost. Recently, hot embossing technique has been proposed to fabricate microstructures on glass substrate. Compared to the above methods, hot embossing is more simple, productivity and the quality of final products is better. Especially, micro-formability of glass material could be improved with the assistance of ultrasonic vibration.