The influence of flap inclination angle on fluid transport at ciliated walls

In optimizing fluid flow at walls, research has turned to artificial cilia to mimic the propulsion of their whip-like beat of a metachronal traveling wave. Recently we developed a pneumatically actuated micro-membrane device which has rows of long flaps positioned off-center on membranes over a row of cavities, much like the comb row of a ctenophore. As little is known about how the flap inclination angle influences the fluid transport near the wall of such devices, this paper presents a detailed modeling and experimental investigation of this question using combined FEM-FVM (finite element method-finite volume method)-based simulations for inclination angles of 0 degrees, 20 degrees, 30 degrees, and 45 degrees. The experimental results agree well with those of the FEM-FVM simulations. Antiplectic fluid transport was observed for flap inclination angles lower than 20 degrees whereas symplectic fluid transport was determined for those higher than 20 degrees. In conclusion, the inclination angle of the flaps decisively affects the fluid transport direction and velocity.