Taming the Coffee Ring Effect: Enhanced Thermal Control as a Method for Thin-Film Nanopatterning

Abstract

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.

Quantification of Desiccated Extracellular Vesicles by Quartz Crystal Microbalance

“…During the evaporation of a droplet on a substrate, a deposit of concentrated particles often tends to appear in the form of a ring-shaped pattern that is commonly referred to as the “coffee ring”. This coffee ring effect was first introduced by Deegan R. D. et al [ 47 ], and this phenomenon has been thoroughly studied both experimentally and theoretically in order to find the determining factors that provide control over the patterns composed of deposited particles [ 48 ]. The application of the coffee ring effect has already had an impact on various fields, such as DNA/RNA microarrays, nanoparticle assembly, and biophysical detection [ 49 ].…”

Inkjet Printing: A Viable Technology for Biosensor Fabrication

“…It is possible to print a smooth and uniform line with uniform edges by controlling the drop frequency, temperature, and spacing, as reported by [231]. Recently, a study by Sliz et al [233] showed both experimentally and through simulation modeling that droplet behavior can be controlled by the substrate's temperature, thus controlling the coffee-ring effect. They showed that up to a critical temperature, an increase in heat transfer causes an increase in the capillary effect, and consequently, an increase in the size of the coffee-ring effect.…”

3D-printed flexible organic light-emitting diode displays

“…One obstacle lies in the nonuniformity of extrusion-printed active layers, owing to the directional mass transport within the printed droplets that is driven by the capillary flow during solvent evaporation ( 27 , 28 ). A second challenge is the creation of repeatable and stable polymer-metal junctions between the active layer and the cathode using the 3D printing approach at room temperature ( 29 , 30 ).…”