NSF Award
2306371
This award is an experimental and computational study of how soft materials flow. The flow of materials like mud, cement, foam, and dirt in landslides is quite different from the flow of liquids. These materials have been studied before but their complexity makes it difficult to determine general principles about how these interesting substances flow. Some past studies used simple systems to try to mimic these complicated materials: a standard simple system is a liquid full of round particles with a specific size. It is clear that these simple systems fail to reproduce many of the interesting flow behaviors of the real materials. This work studies the flow of materials with intermediate complexity: liquids with particles with a mixture of sizes in the same sample. Microscopy is used to view the trajectories of particles in a flowing sample. These observations will be used to develop basic ideas about the flow of disordered materials, which will lead to better understanding of how to move, mix, and process complex materials of industrial relevance. The researchers will regularly host field trips of visiting students (first grade through high school) to teach them about soft squishy materials and how scientists study these materials.<br/><br/>The objective of this award is to understand how amorphous solids flow, in particular to connect particle-scale rearrangements to macroscopic flow profiles and rheological behavior. The main samples to be studied are highly polydisperse emulsions, where the largest droplets are ten times the radius of the smallest droplets; and computational models that mimic these emulsions. Flowing and sheared samples are studied with video and confocal microscopy with a goal of simultaneous tracking of individual droplets for long times. These trajectories will be characterized in terms of magnitudes of displacements, relative motions of neighboring droplets, and cascading rearrangements that might be triggered as the sample flows. Similar analysis will be done for the computational data. These microscopic observations will be connected to macroscopic rheological properties. The overall motivation is to bridge the gap between prior model systems that studied mixtures of particles of fairly similar sizes, and complex real-world materials such as mud and cement. The research team will also host field trips each year to demonstrate to visiting students that cutting edge science can be done with simple materials which they can literally get their hands on.<br/><br/>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.
