A fluid displacement device (100) having a homopolar motor (110). The homopolar motor includes a rotatable disk (115) with at least one fluid displacement structure (120) disposed thereon. The fluid displacement structure can be a blade. The rotatable disk can be disposed within a cavity (145) defined in a substrate (105), such as a ceramic substrate, a liquid crystal polymer substrate, or a semiconductor substrate. A closed loop control circuit (235) can be included to control the rotational speed of the rotatable disk. For example, the control circuit can control a voltage source or a current source that applies voltage across the rotatable disk. The control circuit also can control a strength of a magnet (210) that applies a magnetic field (205) substantially aligned with an axis or rotation (155) of the rotatable disk.