Filter for perfusion cultures of animal cells and the like

A bioreactor comprising:

• a container for fluid, the container being suitable for the cultivation of animal cells under sterile conditions;
• a conduit extending from within the container to outside the container, the conduit having an opening for flow of fluid into the conduit;
• means in the container for stirring the fluid and provide a flow of fluid with a component of flow parallel to the opening to sweep material away from the opening;
• a pump for pumping fluid into the conduit through the opening;
• and
• means for producing a negative dielectrophoretic force on target particles carried by the fluid, wherein the negative dielectrophoretic force is adapted to have a component opposed to the flow of fluid and the component of the negative dielectrophoretic force has sufficient strength to prevent the target particles from passing into the conduit.

A method for filtering target particles from a fluid contained in a bioreactor, the method comprising the steps of:

• pumping fluid from the container into a conduit through an opening in the conduit;
• moving fluid in the container in a direction that includes a component of flow parallel to the opening to sweep material away from the opening;
• and
• applying a negative dielectrophoretic force to target particles at the opening, the negative dielectrophoretic force having sufficient strength to prevent the target particles from entering the conduit.