Principle of tangential flow ultrafiltration? How to separate biomolecules

In tangential flow (also known as cross flow) ultrafiltration, the pump pushes the fluid through the surface of the filter membrane to wash away the trapped molecules, so as to minimize the scale on the surface of the filter membrane. The pressure close to the filter membrane is generated in the residual logistics to make solutes and small molecules pass through the filter membrane. In this way, the filtering can be completed. The simulation experiment of separating sand and pebbles by subdivision screen is helpful to understand the mechanism of tangential flow ultrafiltration: the screen hole symbolizes the pores on the filter membrane, while sand and pebbles symbolize the molecules to be separated. In DC filtration, the sand pebble mixture is forced to move towards the screen hole. As some smaller sand particles fall through the screen hole, a pebble layer is formed on the screen surface, Prevent the top sand from moving towards the screen and passing through the screen mesh. In DC filtration, increasing the pressure can only exert pressure on the mixture, which is not conducive to the promotion of separation; In contrast, in the tangential flow ultrafiltration mode, the formation of the limiting layer is prevented by the recirculation of the mixture, which is similar to vibration to remove the pebbles blocking the screen mesh, so that the sand particles at the top of the mixture fall and pass through the screen mesh. Therefore, the use of tangential flow ultrafiltration for biomolecular separation has higher efficiency and faster concentration or washing filtration speed.