Laser Microtexturing of Surfaces and Applications

Chakraborty, Anustup, Electrical Engineering - School of Engineering and Applied Science, University of Virginia
Gupta, Mool, EN-Elec & Comp Engr Dept, University of Virginia

Surface properties play an essential role in many applications and allow the control of adhesion, wettability, and durability, etc. Surface microtexturing is a well-established method to enhance the surface properties of materials, including fatigue strength, corrosion resistance, anti-biofouling, adhesion, and hydrophobicity. Standard surface microtexturing techniques, such as chemical etching, electrical discharge, sandblasting, micro-milling, ion beam texturing, and lithography, often involve toxic chemicals, lack controllability, require multiple steps, use of elevated temperatures, or heavy equipment. In this thesis, we investigated the laser microtexturing process and its application in two key areas: enhancing the adhesion strength of thermal spray coatings on metallic surfaces and creating superhydrophobic and superhydrophilic surfaces. Laser microtexturing allows the generation of high-quality surfaces in a single, contactless step, addressing the limitations of traditional methods. Surfaces of materials like aluminum, steel, and glass were laser microtextured. A full-area laser microtexturing method was developed based on the thermomechanical rearrangement of surface features with minimal ablation.
The laser-microtextured surface was subjected to a thermal spray process, resulting in the accumulation of metallic particles. Compared to grit-blasted samples, surfaces with a 5 μm deep microtexture exhibited an adhesive tensile strength surpassing grit-blasted samples by over 17%, offering improved durability, resilience, and reduced maintenance costs for metal components.
The laser microtexturing method was also used to demonstrate the fabrication of superhydrophobic and superhydrophilic properties. Furthermore, the controlled transition between superhydrophobicity and superhydrophilicity was explored and a cost-effective laser microtexturing technique for inducing superhydrophilicity was introduced. A thin polydimethylsiloxane (PDMS) coating can transform the laser-microtextured surface into a superhydrophobic state, and this thin layer can be easily removed through laser ablation, enabling a reversible shift between superhydrophilicity and superhydrophobicity. Additionally, the superhydrophobic surfaces created using laser ablation of PDMS achieved water contact angles exceeding 150°, roll-off angles less than 3°, and optical transmission values of over 90% on transparent glass surfaces.
The study of laser microtextured superhydrophilic and superhydrophobic surfaces will impact numerous applications, including self-cleaning surfaces, corrosion protection, anti-icing coatings, microfluidic systems, water collection, and efficient thermal management.

PHD (Doctor of Philosophy)
Laser Microtexturing, Superhydrophobic, Adhesion Strength, Thermal Spray, Suraface Science, Laser-mater Interaction
Sponsoring Agency:
NASA, Commonwealth Institute of Advanced Manufacturing
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