Abstract
Hot embossing is widely used to replicate micro-structures on polymer plate surfaces. The polymer parts of curved surfaces with micro-structures have important functions in various optoelectronic components. However, due to the high precision needed for embossing machines and mold manufacturing, achieving uniform pressure on curved surfaces during the embossing process is difficult. This study modified conventional hot embossing processes to develop an elastic bag embossing system (EBES) for replicating micro-structures on curved surfaces. The pressure equalizing properties of the elastic bag enabled uniform application of pressure on curved surfaces embossed with a general hot compression machine. For the EBES-assisted hot embossing process, a nickel stamper was attached to the elastic bag to compress and replicate micro-structures on the PC film covering the mold surface with single direction curve. This study also developed an EBES-assisted UV exposure process that used a PDMS soft-mold attached to the elastic bag surface to compress the UV curable photoresist covering the surface of the convex lens. Micro-structures were then formed by exposing the photoresist. Experimental results showed that the EBES with Ni stamper could successfully replicated micro-structures onto a 200 mm × 200 mm curved PC film and that the EBES-assisted UV exposure could successfully produced a 50 mm diameter fresnel lens on a convex profile with material of UV photoresist. Experimental tests of pressure-sensitive film showed that EBES enables uniform application of pressure on curved surfaces during the embossing process on standard hot compression machines. The experimental results confirm that the EBES developed in this study is an efficient and economical method for replicating micro-structures on curved surface.
References
Chang, J. H., Yang, S. Y., “Gas Pressurized Hot Embossing for Transcription of Micro-Features”, Microsyst. Technol., 10, 76–80 (2003) 10.1007/s00542-003-0311-1Search in Google Scholar
Chang, J. H., Yang, S. Y., “Developement of Fluid-Based Heating and Pressing Systems for Micro Hot Embossing”, Microsyst. Technol., 11, 396–403 (2005) 10.1007/s00542-004-0481-5Search in Google Scholar
Chang, W. Y., Wu, J. T., Lin, K. H., Yang, S. Y., Lee, K. L. and Wei, P.K., “Fabrication of Gold Sub-Wavelength Pore Array Using Gas-Assisted Hot Embossing with Anodic Aluminum Oxide (AAO) Template”, Microelectro. Eng., 88, 909–913 (2011) 10.1016/j.mee.2010.12.016Search in Google Scholar
Cheng, F. S., Yang, S. Y., Nian, S. C. and Wang, L. A., “Soft Mold and Gasbag Pressure Mechanism for Patterning Submicron Patterns onto a Large Concave Substrate”, J. Vac. Sci. Technol., 24, 1724–1727 (2006) 10.1116/1.2209991Search in Google Scholar
Greener, J., Li, W., Ren, J., Voicu, D., Pakharenko, V., Tang, T. and Kumacheva, E., “Rapid, Cost-Efficient Fabrication of Microfluidic Reactors in Thermoplastic Polymers by Combining Photolithography and Hot Embossing”, Lab Chip, 10, 522–524 (2010) 10.1039/b918834gSearch in Google Scholar PubMed
Jena, R. K., Yue, C. Y., Lam, Y. C., Tang, P. S. and Gupta, A., “Comparison of Different Molds (Epoxy, Polymer and Silicon) for Microfabrication by Hot Embossing Technique”, Sens. Actuators, B, 163, 233–241 (2012) 10.1016/j.snb.2012.01.043Search in Google Scholar
Li, J. M., Liu, C., Qiao, H. C., Zhu, L. Y., Chen, G. and Dai, X. D., “Hot Embossing/Bonding of a Poly(ethylene terephthalate) (PET) Microfluidic Chip”, J. Micromech. Microeng., 18, 015008 (2008) 10.1088/0960-1317/18/1/015008Search in Google Scholar
Mathur, A., Roy, S. S., Tweedie, M., Mukhopadhyay, S., Mitra, S. K. and McLaughlin, J. A., “Characterisation of PMMA microfluidic channels and devices fabricated by hot embossing and sealed by direct bonding”, Curr. Appl. Phys., 9, 1199–1202 (2009) 10.1016/j.cap.2009.01.007Search in Google Scholar
Pan, C. T., Wu, T. T., Chen, M. F., Chang, Y. C., Lee, C. J. and Huang, J. C., “Hot Embossing of Micro-Lens Array on Bulk Metallic Glass”, Sens. Actuators A, 141, 422–431 (2008) 10.1016/j.sna.2007.10.040Search in Google Scholar
Paul, K. E., Prentiss, M. and Whitesides, G. M., “Patterning Spherical Surfaces at the Two-Hundred-Nanometer Scale Using Soft Lithography”, Adv. Funct. Mater., 13, 259–263 (2003) 10.1002/adfm.200304255Search in Google Scholar
Ruchhoeft, P., Colburn, M., Choi, B., Nounu, H., Johnson, S., Bailey, T., Damle, S., Stewart, M., Ekerdt, J., Sreenivasan, S. V., Wolfe, J. C. and Willson, C. G., “Patterning Curved Surfaces: Template Generation by Ion Beam Proximity Lithography and Relief Transfer by Step and Flash Imprint Lithography”, J. Vac. Sci. Technol. B, 17, 2965–2969 (1999) 10.1116/1.590935Search in Google Scholar
Shiu, P. P., Knopf, G. K., Ostojic, M. and Nikumb, S., “Rapid Fabrication of Tooling for Microfluidic Devices via Laser Micromachining and Hot Embossing”, J. Micromech. Microeng., 18, 025012 (2008) 10.1088/0960-1317/18/2/025012Search in Google Scholar
Van Erps, J., Wissmann, M., Guttmann, M., Hartmann, M., Mohr, J., Debaes, C. and Thienpont, H., “Hot Embossing of Microoptical Components Prototyped by Deep Proton Writing”, IEEE Photonic Tech. L., 20, 1539–1541 (2008) 10.1109/LPT.2008.928836Search in Google Scholar
Zhai, M., Lam, Y. C. and Au, C. K., “Runner Sizing and Weld Line Positioning for Plastics Injection Moulding with Multiple Gates”, Eng. Comput., 21, 218–224 (2006) 10.1007/s00366-005-0006-6Search in Google Scholar
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