A new fluid-filtering mechanism inspired by the mouth structure of filter-feeding fish allows particles to be effectively trapped thanks to vortices in the fluids. This mechanism allows particles to be retained, potentially even when the particles are smaller than the mesh size of the filter itself, finds a study in Nature Communications. The findings may be used in a range of industrial applications where effective filtration of fluids is required, such as production of beer and dairy foods.
Filter-feeding fish, such as goldfish and whale sharks, are able to retain food particles without clogging their oral filter with unwanted debris. However, the fluid dynamic processes that enable filter-feeding fish to avoid clogging have been unclear until now.
Laurie Sanderson and colleagues design cone shaped, 3D printed, nylon plastic models inspired by structures known as gill arches in the mouths of paddlefish and basking sharks. They study the models’ activity in an experimental flow tank, as well as the mouth structure of three paddlefish specimens. The authors show that the filtering structures in the models and the fish operate by creating vortices in the fluid that trap food particles and prevent clogging. The gill arches - bony or cartilaginous arches that support the gills - function as specific ribs (so-called ‘d-type’) that help to channel the flow of water in the fish mouth, creating currents and vortices. These ribs help to concentrate small particles, improving the efficiency of food capture.
The authors propose that this mechanism - so-called ‘vortical cross-step filtration’ - can be extended to other filter feeding organisms with similar oral architecture, such as tadpole gill filters, duck beak lamellae and whale baleen plates. The findings may also pave the way for more efficient industrial filters to be designed, potentially leading to more efficient filter processes.