This project examines the mechanical properties of liquid interfaces that are coated by small particles. When the number of particles on a liquid interface is large, the particles can form arrangements called mesostructures, which can change the mechanical stiffness, permeability, appearance, or other properties of the interface. The project will use a combination of experiments, theory, and numerical calculations to show how mesostructure formation affects mechanical properties of the interface. Interfaces covered with particles appear in a wide variety of technological and biological applications including microcapsule formulations for food products and drug delivery, separations in mining operations, and improved, low-toxicity dispersants for treating oil contamination in bodies of water. The information obtained in this project will provide new methods for scientists and engineers to predict, analyze, and control the mechanical properties of interfaces, which can lead to innovative and mechanically robust products. This project will also support the training of undergraduate and graduate students for careers in science or engineering, and it will support outreach to K-12 students and teachers.
Particle-coated interfaces, called particle sheets, will be fabricated and their stiffness (moduli) for stretching and bending will be measured. Particle sheets will be subjected to stress or geometric distortion to identify three distinct responses, wrinkling or buckling, tearing or cracking, and the formation of particle-packing defects such as disclinations or dislocations. The response of a particle sheet to uniaxial compression will provide the bending modulus. The response to point-like forces imposed on the sheet by poking will provide the stretching modulus. Changing the curvature of a particle sheet by confining it on a curved interface will elucidate the competition among wrinkles, cracks and particle-packing defects. The experimental and theoretical activities in this project will lead to the development of a structural relaxation phase diagram for thin sheets composed of particles.
