Taming the coffee ring effect : enhanced thermal control as a method for thin-film nanopatterning
Sliz, Rafal; Czajkowski, Jakub; Fabritius, Tapio (2020-07-22)
Rafal Sliz, Jakub Czajkowski, and Tapio Fabritius, Langmuir 2020 36 (32), 9562-9570, DOI: 10.1021/acs.langmuir.0c01560
© The Authors 2020. This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.
Predicting and controlling a droplet’s behavior on surfaces is very complex due to several factors affecting its nature. These factors play a crucial role in colloidal material deposition and related solution-based manufacturing methods such as printing. A better understanding of the processes governing the droplet in the picoliter regime is needed to help develop novel thin-film manufacturing methods and improve the current ones. This study introduces the substrate temperature as a method to control the droplet’s behavior during inkjet printing, especially the coffee-ring phenomena, at an unprecedented temperature range (25—250 °C). To explain the particular behavior of the droplet, this research associates the creation of specific coffee-ring micro/nanostructures at elevated temperatures with the Leidenfrost effect that is responsible for creating a vapor pocket under the drying drop. Herein, we combine experimental data and numerical methods to explain the drying dynamic of the picoliter-size droplet on the substrate at elevated temperatures. The achieved results indicate that the coffee-ring effect is correlated with the heat-transfer changes caused by the Leidenfrost effect and can be controlled and used to produce micro/nanostructured thin films without additional processing steps.
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