This stepper motor-driven positive displacement pump is engineered to control more challenging fluids reliably, including those with high concentrations of surfactants and fluids prone to crystallization, across an extensive cycle life. It utilizes two seals and two fluidic chambers to isolate the motor from the working fluid. The portion of the piston in contact with the working fluid does not retract past the second seal, and the isolation chamber can be plugged with air, filled with a barrier fluid, or actively flushed to dilute fluid residue on the piston. All designs are equipped with a home sensor to establish the end of stroke and an optical motor encoder to provide feedback on piston movement