Breast pump apparatus

A breast pump apparatus for expressing breast milk, comprising a container unit for receiving expressed breast milk, and a pump unit including a pump body and a pumping device for applying negative pressure to a pump volume defined by the pump body, the pump body comprising an inlet portion adapted to be received on a female breast and an outlet portion adapted to channel expressed milk to the container unit wherein the pump body further comprises an actuator element comprising an active material capable of deforming upon application of a control signal to it and configured to have a bi-stable or multi-stable configuration, wherein deformation of the actuator element modifies at least one of a shape and size of the pump volume and wherein the actuator element is arranged at the pump body distant from the portion designated to be in contact with the female breast, wherein a deformation of the actuator element modifies the volume of the pump volume defined inside the pump body.