A surgical device comprises a base unit having a hydraulic controller and at least one control piston, a surgical end effector including at least one actuator piston, and a flexible shaft having at least one tube containing hydraulic fluid in hydraulic communication with the base unit and the surgical end effector. The hydraulic controller includes an electric motor configured to drive the control piston to generate hydraulic force. The hydraulic force is transferable from the base unit to the actuator piston of the surgical end effector through the hydraulic fluid in the at least one tube in the flexible shaft, such that the driving of the control piston by the electric motor under the control of the hydraulic controller transfers the hydraulic force from the control piston of the base unit to the actuator piston of the end effector in proportion to the ratio of the area of the control piston and the area of the actuator piston by metering the hydraulic fluid transferred by the control piston.