Boundary waves in a microfluidic device as a model for intramural periarterial drainage.

The failure to clear amyloid-Beta from an aging brain leads to its accumulation within the walls of arteries and potentially to Alzheimer's disease. However, the clearance mechanism through the intramural periarterial pathway is not well understood. We previously proposed a hydrodynamic reverse transport model for the cerebral arterial basement membrane pathway. In our model, solute transport results from fluidic forcing driven by the superposition of forward and reverse propagating boundary waves. The aim of this study is to experimentally validate this hydrodynamic reverse transport mechanism in a microfluidic device where reverse transport in a rectangular conduit is driven by applying waveforms along its boundaries. Our results support our theory that while the superimposed boundary waves propagate in the forward direction, a reverse flow in the rectangular conduit can be induced by boundary wave reflections. We quantified the fluid transport velocity and direction under various boundary conditions and analyzed numerical simulations that support our experimental findings. We identified a set of boundary wave parameters that achieved reverse transport, which could be responsible for intramural periarterial drainage of cerebral metabolic waste.