Collaborative Research: ISS: Microgravity enabled studies of particle adsorption dynamics at fluid interfaces

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Particle-laden droplets have received attention for their applications in emulsions, catalysis, sensing, optical materials, as well as environmental remediation. An important step in creating particle-laden fluid interfaces is the transport and attachment (adsorption) of the particles to a fluid droplet. Unfortunately, it is challenging to study directly the attachment process on Earth with the competing effects of sedimentation (gravitational settling) of the particles dispersed in the bulk of the fluid. In other words, there is competition between particles attaching to a fluid interface and settling because of gravity. To alleviate the effect of gravity, this award aims to study adsorption of particles to fluid interfaces under microgravity in the international space station. The project will elucidate the critical steps of how particles attach to droplets in the absence of sedimentation. Findings from this award will lead to engineering strategies to optimize the design of materials that rely on particle-laden interfaces. From a technological standpoint, the knowledge gained will be directly applicable to emerging technologies in additive manufacturing and optical materials to impact life on Earth. The stability of particle-stabilized emulsions strongly depends on the particle coverage at the interface. Kinetic limitations during particle adsorption limit Pickering emulsions from reaching their full technological potential. This award aims to advance our understanding of particle adsorption at interfaces by developing: 1) fundamental knowledge in structure-property (surface pressure-area fraction) relationships at fluid interfaces, 2) an understanding of the transition from fluid to glassy (sluggish) dynamics at fluid interfaces, and 3) a validated model describing diffusion-limited adsorption. This award aims at understanding the mechanisms limiting the adsorption of particles to fluid interface by conducting experiments in microgravity. Microgravity experiments are necessary and allow to investigate adsorption dynamic in the absence of sedimentation. The time scale for gradient diffusion to a fluid interface can be of order of hours, making parabolic flights not a realistic option to avoid gravitational effects. While key experiments will be conducted under microgravity, the scientific and technological impacts of the work will benefit life on Earth. Findings will benefit any processes involving particles adsorption to fluid interfaces including in manufacturing, consumer products, flotation, oil recovery, and environmental remediation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.