Optimizing coffee ring patterns through enhanced thermal control: Effects of artificial temperature gradients

The coffee-ring effect, driven by droplet evaporation, significantly affects the performance of printed films and nanostructured materials. Despite various strategies to mitigate this effect, challenges persist, particularly for suspensions with high solute concentrations. This study investigates the influence of temperature gradients on evaporation patterns using experimental and numerical methods, demonstrating how radial flow within the droplet can modulate capillary flow. We propose a laser-assisted local heating method to control coffee-ring formation by inducing a non-uniform temperature field within the droplet. A thermal vector model is introduced to predict the resulting evaporation pattern morphology. Our findings offer a practical approach for controlling coffee-ring formation and provide insights into temperature-gradient-driven particle deposition.