My major research interest is the experimental study of complex fluids using bulk and microrheology techniques.

A photo collage of fluids
Complex fluids (via Wikipedia.org)

“Complex fluids” generally refers to the class of materials that are solid in one circumstance while flow at another. Examples of complex fluids includes crude oils, plastic melts, inks, asphalts, toothpastes, chocolates, and bloods, etc. In a certain sense, complex fluids simply lay the foundation of modern life and industry. The solid-liquid duality is the most important characteristics of complex fluids. For example, toothpastes squeezed from the tube stands on the brush, yet fluidized again when teeth-brushing. Other circumstances include extruding, stirring, spraying, chewing, dip coating, lubricating, and gelling. The extent of contrast between the solid and the fluid states in a complex fluid is often several orders of magnitudes.

Despite familiarity, the physics of the time and condition when complex fluids stay in one form or transition to another is difficult, since it often involves off-equilibrium, mesoscopic heterogeneity and nonlinear dynamics that, in some cases, do not even have a plausible hypothesis. Experimental works are therefore crucial to the overall development of this field.

The academic website of Weixiang Sun