Periodic Reporting for period 1 - CoffeeRings (Understanding the drying behavior of polymer-coated particle dispersions using optical tweezers)
Reporting period: 2022-08-01 to 2024-07-31
The "coffee ring effect" leads to the concentration of dispersed particles at the edges of a drying droplet, which poses challenges for technologies like coating and ink-jet printing that require uniform particle deposition. Traditional methods to counteract this effect, such as increasing liquid viscosity or inducing Marangoni flows, often involve complex systems and restrict material flexibility.
In my initial studies, I found that coating dispersed particles with surface-active polymers can effectively mitigate this effect, resulting in a uniform particle film regardless of the particle type, shape, or solvent used. However, my preliminary data were based on an empirical approach—mixing particles with polymers and observing the drying behavior—which provided limited insights. This approach is insufficient for a fundamental investigation because commercial polymers exhibit a broad molecular weight distribution, and the mechanisms of polymer adsorption onto particle surfaces are not well understood. Consequently, a deeper understanding of how polymer coatings influence drying behavior remains necessary.
In my initial studies, I found that coating dispersed particles with surface-active polymers can effectively mitigate this effect, resulting in a uniform particle film regardless of the particle type, shape, or solvent used. However, my preliminary data were based on an empirical approach—mixing particles with polymers and observing the drying behavior—which provided limited insights. This approach is insufficient for a fundamental investigation because commercial polymers exhibit a broad molecular weight distribution, and the mechanisms of polymer adsorption onto particle surfaces are not well understood. Consequently, a deeper understanding of how polymer coatings influence drying behavior remains necessary.
In the COFFEERINGS project, I employed optical tweezers to analyze and quantify the impact of polymer coatings on interactions at each stage of the drying process with single-particle precision. I synthesized a series of core-shell model particles and evaluated their interaction potential based on chain length and pH responsiveness, linking these factors to the drying behavior of dispersions. This approach has yielded fundamental insights into how polymer-coated particles interact with one another and adsorb onto the liquid interface. These findings not only refine particle-polymer-solvent mixtures to prevent the coffee ring effect and ensure uniform particle deposition but also enhance our understanding of particle interactions with liquid interfaces. This knowledge paves the way for developing more efficient methods to create particle-stabilized interfaces.
During COFFEERINGS, we developed a novel method to quantify particle adsorption at liquid interfaces. Our findings revealed that polymers adsorbed onto particles act as catalysts, promoting their adhesion to the liquid interface. This insight allowed us to understand how these polymers mitigate the coffee ring effect and lead to uniform drying.
The modified mini-tweezer setup created during COFFEERINGS has promising applications for characterizing interactions between particles and liquid interfaces. This method is expected to benefit various research fields, including the study of particle interactions with biological membranes and the formation of particle-stabilized foams and emulsions. Additionally, measuring particle interaction potential at liquid interfaces will be invaluable for understanding particle self-assembly.
The modified mini-tweezer setup created during COFFEERINGS has promising applications for characterizing interactions between particles and liquid interfaces. This method is expected to benefit various research fields, including the study of particle interactions with biological membranes and the formation of particle-stabilized foams and emulsions. Additionally, measuring particle interaction potential at liquid interfaces will be invaluable for understanding particle self-assembly.