Process Development of Drawcasting Structures in Thermoplastic Films

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Copenhaver, Katherine
Nadler, Jason
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Polymer surfaces patterned with high-aspect-ratio (AR) micro- or nanostructures are challenging to manufacture on a large scale due to steep fabrication costs and the lack of high-throughput patterning techniques. Furthermore, most surface patterning techniques for high-AR polymer structures performed on a laboratory scale are restrictive in terms of the geometries and materials they can accommodate. In this work, a new process for patterning polymer surfaces with high-AR structures, termed drawcasting, was developed and parameterized. Drawcasting is a viscous deformation process that has been shown to reliably produce arrays of high-AR polymer microstructures whose geometry can be tuned easily by changing a variety of process parameters and has been applied to both thermoplastics and curable resins. The relationship between the properties of the materials used in drawcasting and the process parameters and obtained structures was investigated in this work. The development of the drawcasting system as well as innovations in process optimization techniques such as photo- and soft lithography and microscopy are presented. The process is highly rate-, time-, and temperature-dependent, and it necessitates an understanding of a given polymer’s thermal, wetting, and rheological behavior with respect to the selected process parameters. The properties of three different thermoplastics were investigated as they relate to the drawcasting process. Much of this data was also gathered to support thermofluid models in development. Arrays of three-dimensional structures over a broad range of length scales fabricated using the drawcasting system are presented, and methods to further improve the process in order to fabricate arrays of smaller structures over larger areas are discussed.
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