| dc.description.abstract | The coffee ring phenomenon observed during the evaporation of droplets occurs not only in everyday life but also in applications such as ink-jet printing and coating technologies. The coffee ring effect in these applications can negatively affect product quality and performance, among other factors. In this study, we employed two methods to suppress the coffee ring: varying the substrate temperature and adding different concentrations of surfactant (sodium dodecyl sulfate, SDS). The aim is to achieve a uniform deposition pattern. During the droplet evaporation process, four major factors influenced the droplet: capillary flow, surface tension gradients, Marangoni flow induced by temperature gradients, and the descent of the droplet interface. All of these factors can affect the final droplet deposition.
This study conducted experiments at three different temperatures (30˚C, 50˚C, and 70˚C) and with four different SDS concentrations (0 wt %, 0.05 wt %, 0.50 wt %, and 1.00 wt %). The experimental results reveal that coffee ring deposition pattern only occurs when the substrate temperature is at 30˚C and the SDS concentration is low (0 wt % and 0.05 wt %). Increasing the SDS concentration or raising the substrate temperature leads to most particles being depositing within the droplet or in its central region, demonstrating the suppression of the coffee ring phenomenon.
Keywords: coffee-ring phenomenon, inkjet printing, surfactant | en_US |