Observing phase separation in colloid-polymer mixtures with a custom light-sheet rheoscope
Date:
Excerpt of abstract: We study liquid-liquid phase separation (LLPS) with a colloid-polymer system subjected to shear. Our colloid-polymer mixture consists of temperature-responsive PNIPAM microgel particles and polymers acting as a depletant. This mixture separates into two phases: a colloid-poor, or “gas” phase, and a colloid-rich, or “liquid” phase. We observe the process of phase separation using a custom-built light-sheet microscope, which allows for simultaneously acquiring optically-sectioned images of our sample and shearing the sample in a Couette geometry. We measure the size and shape of elongated liquid domains that have been deformed due to flow as a function of shear rate. The temperature-responsive feature of our colloidal particles allows us to further explore the kinetics of phase separation under shear flow. We hope our study of phase separation under shear can provide fundamental insights into hydrodynamics and thermodynamics and provide novel strategies for structuring soft materials.