Understanding the drying behavior of polymer-coated particle dispersions using optical tweezers

Project Information

CoffeeRings

Grant agreement ID: 101064381

DOI

10.3030/101064381

Project terminated on 30 June 2024

EC signature date 5 July 2022

Start date 1 August 2022

End date 31 July 2024

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 222 727,68

Coordinated by

GOETEBORGS UNIVERSITET
Sweden

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

Summary of the context and overall objectives of the project

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.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

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.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

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.

Coffee Ring Outreach at Gothenburg Science Festival