Effective diffusion coefficient and average drift velocity for a bioinspired drift ratchet

Diatoms are microscopic, phototrophic, unicellular algae encased in a porous, rigid, siliceous, cell wall known as the frustule. They inhabit the euphotic zones in bodies of seawater and freshwater. The nutrient and trace element sorting characteristics of the diatoms frustule is not yet fully understood. It has been proposed that the girdle band pores of the marine diatom species (Coscinodiscus sp.) uses the drift ratchet mechanism to sort and separate nutrients and trace elements from harmful particles (i.e. viruses), based on the particle size. From initial numerical simulation results the girdle band pores do exhibit drift ratchet behaviour for a range of fluid flows. The theory requires further comprehensive analysis of the girdle band pores be undertaken, as the hydrodynamic and thermal environment in which the diatom exist is not understood as of yet.