Photodirecting surface energy driven Marangoni convection to pattern thin polymer films
Significant research effort in the last several decades has been devoted to controlling surface topography at different length scales. Especially important are the micro- to nano-meter length scales because of their overarching importance in a variety of applications including cell biology, tissue engineering, coatings, optics, and microelectronics. While the requirements of many applications are well-served by conventional patterning methods such as photolithography and contact printing, there still remains a need for processes possessing eco-friendly and non-contact fabrication steps. These aspects are particularly crucial in laboratory and industrial settings where access to expensive clean room infrastructure, use of toxic developing solvents, and etching protocols required for conventional methods are often not readily available. Bearing the aforementioned perspective in mind, my research topic has been focused on developing a new polymer film patterning method by photodirecting Marangoni flow in thin films. The Marangoni effect causes liquids to flow towards localized regions of higher surface tension. In a thin film, such flow results in smooth thickness variations and may represent a practically useful route to manufacture topographically patterned surfaces. This document describes my research efforts first focused on fundamentally understanding the Marangoni effect. This fundamental understanding is then exploited for developing and optimizing a number of different materials and processing protocols that enable generalization of the approach as a polymer film patterning method. Finally, taking these findings in entirety, this thesis suggests this eco-friendly and non-contact fabrication approach could potentially be implemented in high-throughput manufacturing environments.