Wash through pipettor

A pipettor comprising an actuator assembly and a piston assembly, the actuator assembly comprising:

• an actuator frame;
• linear bearings within and connected to the actuator frame;
• an actuator plate moveable on and along the linear bearings;
• a ball screw;
• a ball screw nut connected to the ball screw;
• and
• an actuator motor positioned on a top end of the actuator frame, wherein the actuator motor is configured to turn the ball screw to drive the ball screw nut that is connected to the actuator plate to move the actuator plate along the linear bearings,
• the piston assembly comprising:
• a top seal plate;
• a cylinder block;
• a wash plate including a wash chamber, the wash chamber defined by a space between the top seal plate and the cylinder block suitable for containing wash fluid;
• a piston plate coupled to the actuator plate;
• a plurality of channels that pass through the top seal plate and the cylinder block;
• a plurality of pistons positioned in and movable in respective channels of the plurality of channels, a first end of each of the plurality of pistons coupled to the piston plate;
• and
• an upper seal and a lower seal configured to isolate the plurality of pistons from the wash chamber,
• wherein the actuator assembly is coupled to the piston assembly for advancing and retracting the plurality of pistons in the respective channels, and wherein the plurality of channels is fluidly coupled with the wash chamber such that retraction of the plurality of pistons causes the pistons to lose sealing contact with the lower seal.