This project represents a comprehensive investigation of the individual dynamics and the collective interactions of vesicles, capsules, and capsule/particle mixtures. The collaborative research is a synergistic effort between high performance computer (HPC) simulations of multiphase flow phenomena as well as detailed experiments using microfluidics and microrheology. Novel aspects of the simulation algorithm include a smooth particle mesh Ewald boundary element code employing both spectral, Loop subdivision, and boundary element resolution of the deforming and interacting interfaces. Essentially, arbitrary shear, bending, and dilatational moduli in the interfacial modeling can be included thus allowing the full range of dynamics from capsules to vesicles including rigid particles and mixtures to be simulated in complex microfluidic geometries. Moreover, nonBrownian and Brownian suspensions can be simulated with high resolution of the interfaces. The experiments include direct visualization, via fluorescence microscopy, of the detailed time varying dynamics of vesicles, and, by creative interfacial chemistry, capsules with varying shear modulus in (a) the microfluidic four roll mill device (capable of reproducing any planar mixed flow in the vicinity of a stagnation point at which the vesicle/capsule may be trapped and observed for extended times) and (b) microchannel geometries designed for examination of collective suspension dynamics. Experiments will also focus on measurements, through fluorescence microscopy and particle tracking, of the shear-induced diffusion of particles and the rheological behavior as the confinement length scale is varied. Applications including understanding platelet hemostasis in the microcirculation as well as engineering vesicles for medical applications.
