(221d) Using Textured Surfaces To Separate Microcapsules

The need to identify diseases on the spot mandates low-cost and efficient separation techniques for biological cells. We show that, for a similar system of artificial microcapsules, separation can be achieved based on mechanical properties by employing a simple fork geometry with different chemical and mechanical textures on the substrate. We study the dynamics in this system using a coupling of the lattice-Boltzmann method for fluid flow and lattice-spring model for an elastic particle and the substrate. The geometry consists of an adhesive delivery patch and two branches. One of the branches is both mechanically and chemically textured while the second one is only chemically textured, however, with a higher adhesive interaction. The interplay between the substrate and capsule deformability and the difference in adhesive properties of the two patches leads to a separation based on mechanical properties of the capsules. The stiffer capsules passively follow the mechanically patterned soft branch whereas softer capsules actively make a decision to follow the more adhesive branch. We present a systematic study of the effects of various parameters, such as the shear rate of the host fluid, mechanical and chemical properties of both the branches and the delivery patch.