Flow of complex suspensions

The flow of complex suspensions is ubiquitous in nature and industrial applications. These suspensions are made of complex particles (anisotropic, deformable, or active) suspended in simple fluids. The macroscopic non-Newtonian properties of these suspensions depend on the nature of the suspended particles and their interaction with given flows. Here, we describe how one can make use of novel micro-fabrication techniques and microfluidic rheometers to determine their flow properties under well controlled experimental conditions. We discuss three different aspects important for the study of the flow of complex suspensions. First, we use a well known complex fluid to design a novel microfluidic rheometer. Then we measure the non-Newtonian shear viscosity of a dilute suspension of microswimmers adapting an existing microfluidic rheometer. And finally we use a micro-fabrication technique to produce well controlled model fibers inside microfluidic channels and give some examples of the flow dynamics when these model fiber suspensions are forced through constrictions.