Control of coffee-ring formation by vertical thermal gradients in confined droplets

Abstract The coffee ring effect is a common manifestation of evaporative self-organization. Conventional strategies to control this effect, such as particle modification or surfactant addition, can be effective but often compromise the intrinsic physicochemical properties of substrates, solvents, or particles, thereby limiting their applicability. This study demonstrates a versatile route for modulating coffee-ring deposition, providing a complementary strategy for controlling evaporative self-organization in functional coatings and droplet-based material processing.