The performance of helical inserts in existing tubular filters has been investigated by Bellhouse et al. [12]. The insert and filter combination was found to deliver high filtration fluxes at low cross-flow rates over a wide range of applications, covering reverse osmosis to microfiltration. In addition the flow shear stresses were viscous, and fluids containing delicate organisms, such as marine algae, were concentrated without damage. The increased fluxes were attributed to the generation of corkscrew vortices, formed by the interaction of Dean vortices and an axial flow component. If this explanation is correct, it should be possible to generate similar corkscrew vortices in internal helical passages, which surround a central lumen. By coating the internal surface of the helical passages with a suitable membrane, a one-piece filter, capable of emulating the performance of the insert and tubular filter, could be constructed. Ruiz et al. [ 16] had demonstrated their ability to produce ceramic filters with internal helical grooves, and the Laboratoire des Materiaux et Procedes Membranaires at Montpellier University produced a number of prototype filters to a design derived from the geometries used in [12]. These filters were tested using high concentrations of bakers' yeast. Similar fluxes to those obtained with the inserts and tubular filters were achieved, over the same range of flow rates. Whilst the mechanism of concentration polarisation reduction by corkscrew vortices works over the whole range of filtration applications, the unique combination of viscous flow, high fluxes, low cross-flow rates and high feed concentrations is particularly suited to microfiltration in bio-processing applications.