Geometric Tools for Controlling Platelet Adhesion

Surfaces are ubiquitous in nature and technology. While natural surfaces excel in self-renewal and preventing bio-fouling, synthetic materials placed in contact with complex fluids like blood quickly foul. We present a novel biophysics inspired strategy for synthetic surface renewal using actuating surface topography. Using experiments, simulation, and theory, we study a general mechanism by which an adhered adlayer detaches from a surface undergoing wrinkling. We calculate a critical surface curvature beyond which surface renewal occurs. The scaling law is well validated using finite element simulations and physical experiments. While the de-adhesion model is deterministic, a statistical analogue is developed to study the effect of topography actuation in dynamically growing fouling adlayers such as platelet aggregates from blood contact. Using a system of actuating cylindrical grafts with varying wrinkle wavelengths placed in contact with whole blood, we show a dramatic over 90% decrease in platelet surface adhesion with topographic actuation. Moreover, the predictions of our statistical model are in strong agreement with the blood experiment data. Our cylinder data complement a second set of platelet adhesion data performed on PDMS surfaces and general mechanism is validated using macroscopic silicone patch experiments. The composite cylinders have been tuned for optimal actuation with arterial pulse pressure variation to function as a novel bypass graft.