441453 Silica Microsphere Assembly

Monday, November 9, 2015
Exhibit Hall 1 (Salt Palace Convention Center)
Lyle A. Menk, Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM

Beginning in May 2015, I have had the opportunity to work with my faculty mentor, Prof. Sang M. Han and his graduate research assistant, Sarun Atiganyanun.  Prior to being assigned a specific project, I first participated in optimizing the Langmuir-Blodgett assembly of microspheres that are size-focused by density gradient centrifugation.  I then learned about silicon substrate etching techniques, such as deep reactive ion etching.  I also learned how the etch profiles in the substrate were examined by scanning electron microscopy.

The purpose of my project is to produce unique silica microsphere assemblies and to assess the optical properties of these structures.  Prior to microsphere assembly, channels must be etched into a silicon substrate.  Microspheres are then assembled into the channels, and a thin adhesive tape is laid over the channel-etched silicon substrate.  The tape, along with a microsphere layer, is carefully removed from the substrate.  Multiple layers of microsphere-coated tape are then stacked in various patterns to create structures with interesting optical qualities.  The adhesive is burned off, ideally leaving only the silica microsphere assembly behind.  The assembly’s structures and optical properties are then characterized.  To properly coat only the channels with the silica microspheres, one must have an understanding of the surface chemistry of the microspheres and each of the surfaces on the substrate.  Other key concepts, such as the periodicity of the channels and the resulting light scattering efficiency must be used to optimize the assembly.  Lastly, the adhesive must be carefully chosen, so that it burns off with minimal impact on the quality of the assembly.  The results of this unique project can be applied to future experimentation on the wide range of optical, thermal, photochemical, and biological applications of silica microsphere assemblies.

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