An apparatus, comprising: a downhole tool for conveyance within a wellbore extending into a subterranean formation, wherein the downhole tool comprises: a moveable member (310, 520) comprising: opposing first and second piston heads of different sizes; a first surface defining a moveable boundary of a first chamber; wherein the first surface is a first surface of the first piston head; the first chamber is a first working chamber; and a second surface defining a moveable boundary of a second chamber wherein the second surface is a first surface of the second piston head; the second chamber is a second working chamber; wherein a second surface of the first piston head defines a moveable boundary of a sampling chamber in selective fluid communication with the subterranean formation; a second surface of the second piston head defines a moveable boundary of a third working chamber; a high-pressure chamber containing fluid at a first pressure, a low-pressure chamber containing fluid at a second pressure that is substantially less than the first pressure; and hydraulic circuitry including: a first valve configured to fluidly connect the first working chamber to the high-pressure chamber in a first position, thereby exposing the first working chamber to the first pressure and translating the moveable member (310, 520) in a first direction, and configured to fluidly connect the first working chamber to low-pressure chamber in a second position, thereby exposing the first working chamber to the second pressure and translating the moveable member in a direction opposite to the first direction; a second valve configured to fluidly connect the third working chamber to the high-pressure chamber in a first position and low-pressure chamber in a second position; and at least one flowline configured to fluidly connect the second working chamber to the low- pressure chamber. a moveable member (310, 520) comprising: opposing first and second piston heads of different sizes; a first surface defining a moveable boundary of a first chamber; wherein the first surface is a first surface of the first piston head; the first chamber is a first working chamber; and a second surface defining a moveable boundary of a second chamber wherein the second surface is a first surface of the second piston head; the second chamber is a second working chamber; wherein a second surface of the first piston head defines a moveable boundary of a sampling chamber in selective fluid communication with the subterranean formation; a second surface of the second piston head defines a moveable boundary of a third working chamber; opposing first and second piston heads of different sizes; a first surface defining a moveable boundary of a first chamber; wherein the first surface is a first surface of the first piston head; the first chamber is a first working chamber; and a second surface defining a moveable boundary of a second chamber wherein the second surface is a first surface of the second piston head; the second chamber is a second working chamber; a high-pressure chamber containing fluid at a first pressure, a low-pressure chamber containing fluid at a second pressure that is substantially less than the first pressure; and hydraulic circuitry including: a first valve configured to fluidly connect the first working chamber to the high-pressure chamber in a first position, thereby exposing the first working chamber to the first pressure and translating the moveable member (310, 520) in a first direction, and configured to fluidly connect the first working chamber to low-pressure chamber in a second position, thereby exposing the first working chamber to the second pressure and translating the moveable member in a direction opposite to the first direction; a second valve configured to fluidly connect the third working chamber to the high-pressure chamber in a first position and low-pressure chamber in a second position; and at least one flowline configured to fluidly connect the second working chamber to the low- pressure chamber. a first valve configured to fluidly connect the first working chamber to the high-pressure chamber in a first position, thereby exposing the first working chamber to the first pressure and translating the moveable member (310, 520) in a first direction, and configured to fluidly connect the first working chamber to low-pressure chamber in a second position, thereby exposing the first working chamber to the second pressure and translating the moveable member in a direction opposite to the first direction; a second valve configured to fluidly connect the third working chamber to the high-pressure chamber in a first position and low-pressure chamber in a second position; and at least one flowline configured to fluidly connect the second working chamber to the low- pressure chamber.