Developing simple methods to suppress the coffee-ring effect without modifying colloidal suspensions (e.g., inherent properties of the solute or solvent) is critical for related industrial and bio-medical applications. This study experimentally investigates adding air bubbles in droplets as a means of suppressing the coffee-ring effect. The added air bubbles induce a concave meniscus and an increased receding contact angle, resulting in fast and smooth retreating of the three-phase contact line and a relatively uniform stain pattern. This method can be employed to droplets at a volume ranging from 2.5 μL to 0.1 mL. These findings can be easily exploited to modulate the drying process and the morphology of stain patterns, with potential applications in scientific and industrial fields.

开发简单的方法来抑制咖啡环效应而不改变胶体悬浮液（例如溶质或溶剂的固有特性）对于相关的工业和生物医学应用至关重要。这项研究实验性地研究了在小滴中添加气泡以抑制咖啡环效应的方法。所添加的气泡会导致弯月面凹进并增加后退接触角，从而导致三相接触线快速顺畅地后退，并产生相对均匀的污点图案。该方法可用于液滴的体积范围从2.5μL到0.1 mL。这些发现很容易用于调节干燥过程和污渍图案的形态，在科学和工业领域具有潜在的应用。