Date of Graduation

8-2011

Document Type

Thesis

Degree Name

Master of Science in Microelectronics-Photonics (MS)

Degree Level

Graduate

Department

Graduate School

Advisor

Ajay Malshe

Committee Member

Min Zou

Second Committee Member

Ken Vickers

Third Committee Member

Z. Ryan Tian

Abstract

Atmospheric icing event is problematic for outdoor structures because it can damage, slow, impede, and danger general routine. For a wind turbine blade, it can damage, disrupt movement, and cause potentially dangerous ice throw. Anti-icing based on a surface texture is advantageous due to the low cost of maintenance and there is no additional requirement of energy output for preventing the icing problem. This work is based on the biomimicry of the superhydrophobic nature of the lotus leaf, whereas the limited wettability supports the water to flow freely from the surface structure. The phenomenon is based on a morphology and composition of the micro-nano scale hierarchical surface features: papilla, micro-pillars, coated in wax nanostructures. The objective of this research is the creation and testing of a surface texture, similar to the lotus formed onto the surface structure of polyurethane coatings. The hypothesis is that a micron size surface texture will prevent the water from penetrating the surface features based on the water's surface tension. Also, it is hypothesized that due to the decreased wetting contact between the water and surface, there is a delay in the time for the water to freeze. The thesis objective was realized through a soft lithography imprinting of a surface texture from a created template. A short timed acid texture created the additional submicron-nanostructure on the surface, resulting in a coating modification with similar structure to the lotus. Characterizations of the coatings were performed using Contact Angle Measurements (CAM), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Optical Microscopy (OM) and Surface Profilometer (SP). The textured polyurethane surfaces showed an increase of the water contact angles as compared to the non-textured surfaces. The air trapped within the surface texture forced the water to bead-up on top of the surface structures. The texture surfaces gave a decrease in the ice to surface contact area consequently resulting in the delayed icing mechanism.

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