The invention relates to a device for pumping a fluid into a bioreactor. Polsatile pumping is made possible by valve arrangement so that growth of the cells in the bioreactor is increased. Pumping function can be achieved though several mechanisms. A piston can be displaced in a cylinder, especially by an electromagnet, wherein a permanent magnet or likewise an electromagnet can be arranged in the piston. The piston can also be displaced by compressed air. An elastic, hollow body can also be provided, wherein said hollow body can be deformed by mechanical electromagnetic forces so that pumping function is achieved by a change in volume. The pumping device can also be used as implant for assisting or replacing heart function.