A miniature pump device, with a fluid reservoir that can contain an intravenous drug, hydraulic fluid, or the like. The miniature pump has a motor disposed adjacent the fluid reservoir, and a piston disposed within the fluid reservoir. A power transfer linkage transfers power from the motor to the piston in the fluid reservoir, and a stationary flexible seal is coupled between the fluid reservoir and the power transfer linkage to seal a portion of the power transfer linkage within the fluid reservoir.