Fabrication and Characterization of Photolithographically Patterned Rough Surfaces Demonstrating Extreme Contact Angle Behavior

• Author / Creator

  Koch, Brendan M

• This thesis features experimental work done to fabricate and characterize silicon surfaces patterned using photolithographic techniques, both standard and novel, to produce a variety of surfaces with roughness of controlled geometric properties. In specific, one set of the surfaces fabricated had pillars with vertical sidewalls to explore the effects of feature size on contact angle, and another set of surfaces had pillars with undercut geometry to test for superoleophobicity. Contact angles were measured on these surfaces using three different test fluids: water, ethylene glycol, and hexadecane. This allowed for a broad range of surface tensions to be examined and thus for a variety of behaviors to be observed during characterization. In analyzing the data new complexities already seen in the literature but not fully explored became apparent. In order to understand these complexities a new framework was developed to empirically describe how liquids behave on rough surfaces such as the ones that were fabricated. This new framework has provided considerable insight and has greatly improved understanding of the behavior of contact angles on the fabricated surfaces and other surfaces in the literature. The framework has allowed us to better understand how drops on textured surfaces behave and how measurements relate to various methods of understanding contact angles, such as the Cassie and Wenzel equations. This is particularly important when assessing surfaces with novel texturing features such as the overhanging cap structure and comparing their behaviors with that of surfaces better characterized in the literature such as surfaces with vertical sidewall pillars, and being able to more accurately and precisely determine what the strengths and weaknesses of these new surfaces really are.

• Subjects / Keywords

  • Superhydrophobic
  • Photolithography
  • Superoleophobic
  • Contact angle

• Graduation date

  Fall 2014

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3VT1GZ2K

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.