Designing Active Surface Structures to Regulate Heat Transport in Microchannels

We used three dimensional computer simulations to examine heat transport in a microchannel that encompasses a periodic array of biomimetic synthetic cilia. We modeled two different configurations of tilted cilia. Both configurations consisted of a grid of evenly spaced cilia with length L and square cross-section 0.1L×0.1L. The cilia were spaced at a distance δx between cilium rows and the inter-cilia spacing in the rows was fixed at δz = 0.25L for one configuration and δz = 0.5L for the other. The channel was filled with a viscous fluid and its top and bottom walls were maintained at different temperatures. The cilia were attached to the bottom channel wall at a specific angle and were actuated by a periodic external force applied vertically to their free ends. The periodical beating of cilia induces fluid mixing inside the fluid that facilitates heat transport. To model this multi-component system, we employed a thermal lattice Boltzmann model coupled with the lattice spring model. In order to investigate how the active cilia affect the heat transfer between the channel walls we varied three parameters in the system. Specifically, we systematically changed the tilt of the cilia, the spacing between cilia and the oscillation frequency of the cilia. Our investigations have allowed us to determine the optimal conditions for using cilia to increase the heat flux from a heated surface. Our findings could be useful for developing new methods for temperature control in microscale devices.