Abstract: The pump has a chamber in which a piston reciprocates to pump a liquid. The piston is moved by having secured thereto the armature of at least one electromagnet (preferably two). The coil of the electromagnet is suitably external of the pump casing. A control circuit pulses the electromagnet at a predetermined rate to provide a predetermined periodic output.In a preferred form, the pump is mounted together with a liquid reservoir on a printed circuit board, and the unit is encapsulated for implantation in the human body to infuse a liquid medicine at a controlled rate into the bloodstream.