Red blood cells(rbcs) in the presence of macromolecules(proteins, polymers etc.) aggregate to form stacked coin like linear structures called rouleaux. The shape selective aggregation here is not governed by the brownian motion of the monomer unit as is common with most self assembling systems but instead is dictated by the deformability of rbcs. This non brownian type shape selective self assembly of rbcs makes it an interesting system to understand assembly phenomena at the microscale. Our goal in this project is to study the effect of deformability of cells in self assembly. We are using a microfluidic system to mix the red blood cell solution with a polymer solution and study the kinetics of aggregation of cells using optical microscopy under different flow conditions. We are also developing a theoretical model for aggregation that takes into account effect of shape, size, hydrodynamics and deformability of red blood cells. We expect to relate the findings of theoretical and experimental approach to gain insight on the role of deformability in aggregation.