SOLUTION PROCESSING OF STRIPES, PATCHES AND DIGITAL PATTERNS USING A NOVEL SLOT DIE COATING-INSPIRED APPROACH
Parsekian, Ara W.
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In recent decades, printing and coating techniques have received interest for manufacturing of low-cost wearable electronics, sensors, displays, photovoltaics, and energy storage devices. The functionality of these devices depends significantly on the print resolution, with typical feature sizes ranging from millimeters to microns. Although feature sizes across this range are technically feasible with established techniques, processing at commercial scale has emerged as a persistent modern challenge. To address this challenge, this dissertation develops an approach that combines the wide-area advantages of slot die coating with a sophisticated patterning capability. Experimental and analytical investigations are carried out to evaluate the pattern complexity and minimum feature size achievable with this approach, to determine the coupling between process parameters and pattern output, and to establish constraints on material formulation that are unique to the process. The first investigation explores the role of wetting and spreading in a narrow coating bead as phenomena that mediate pattern output. The second investigation considers co-deposition of two materials to form alternating continuous stripes in a single processing step. Finally, co-laminar internal flow of two materials is investigated as a mechanism for reducing feature size and manipulating pattern morphology. Using this approach, fine-pitch features smaller than 50 µm are demonstrated in a wide-area coating process with commercially available conductive inks.