A flow-control system (100, 150) comprising: a fluid reservoir (102, 154) configured to store a fluid (112, 156); a pressure accumulator (104, 152, 304) in flow communication with and positioned downstream from the fluid reservoir; a loading zone configured to receive and fluidly couple to a flow cell having a biological or chemical sample, the loading zone being in flow communication with and positioned downstream from the pressure accumulator; and a system pump (110, 158) in flow communication with and positioned downstream from the loading zone, the system pump configured to induce a flow of the fluid from the fluid reservoir and through the pressure accumulator and the loading zone; wherein the pressure accumulator includes a wall actuator and an interior chamber (186, 254) that is defined by a movable chamber wall (184, 258, 260, 282) and has an operating volume, a processing unit configured to selectively control the system pump to induce flow of the fluid through the flow-control system and selectively control the pressure accumulator to assist the system pump in delivering the fluid to the flow cell,wherein the processing unit is configured to control the wall actuator to selectively move the chamber wall and thereby change the operating volume of the interior chamber, the pressure accumulator being configured to receive fluid into the interior chamber from the fluid reservoir during a filling operation of the interior chamber (186, 254), wherein the processing unit is configured to control the wall actuator to move the chamber wall to impart pressure on the fluid and drive the fluid toward the loading zone during a pressure-assist operation. a fluid reservoir (102, 154) configured to store a fluid (112, 156); a pressure accumulator (104, 152, 304) in flow communication with and positioned downstream from the fluid reservoir; a loading zone configured to receive and fluidly couple to a flow cell having a biological or chemical sample, the loading zone being in flow communication with and positioned downstream from the pressure accumulator; and a system pump (110, 158) in flow communication with and positioned downstream from the loading zone, the system pump configured to induce a flow of the fluid from the fluid reservoir and through the pressure accumulator and the loading zone; wherein the pressure accumulator includes a wall actuator and an interior chamber (186, 254) that is defined by a movable chamber wall (184, 258, 260, 282) and has an operating volume, a processing unit configured to selectively control the system pump to induce flow of the fluid through the flow-control system and selectively control the pressure accumulator to assist the system pump in delivering the fluid to the flow cell,wherein the processing unit is configured to control the wall actuator to selectively move the chamber wall and thereby change the operating volume of the interior chamber, the pressure accumulator being configured to receive fluid into the interior chamber from the fluid reservoir during a filling operation of the interior chamber (186, 254), wherein the processing unit is configured to control the wall actuator to move the chamber wall to impart pressure on the fluid and drive the fluid toward the loading zone during a pressure-assist operation.