A cartridge (2) for use in an electrowetting sample processing system, the cartridge (2) comprising at least one inlet port (19') for introducing an input liquid (60, 61) in an internal gap (6) of the cartridge (2), wherein the gap (6) comprises at least one hydrophobic surface (17) and is configured to provide an electrowetting induced movement of a microfluidic droplet (23) of input liquid (60, 61), wherein the input liquid (60, 61) comprises a carrier liquid (60) and a processing liquid (61) and the gap (6) comprises a capture zone that is configured to capture at least a part of the processing liquid (60,61) as a microfluidic droplet (23) by use of electrowetting force and the gap (6) further comprises a transfer zone that is configured to provide a passage for the carrier liquid (60) next to the microfluidic droplet (23), while processing liquid (61) is captured in the capture zone (62).