Nature's design principles of manta ray filter lobes

Manta rays feed on zooplankton using a specialized filtration apparatus featuring arrays of filter lobes, which deflect food particles away from the filter surface. Although this ricochet functionality shows promise for anticlogging filtration, the structure-property relationship governing this phenomenon remains unclear. We investigate nature's design principles of manta rays filter lobes and draw inspiration for microfiltration. We propose a generic filter structure and construct a scaling law to characterize the leakage flow through the gaps of the filter lobes. The scaling law is then validated through simulations and experiments. By further incorporating the gap-level scaling law into a macroscopic leaky channel model and analyzing particle trajectories, we establish the trade-offs between water permeability and particle selectivity. Our findings reveal that the manta-ray-inspired filter structure achieves an optimal balance between permeating water and ricocheting zooplankton-sized particles.