Disclosed herein are devices, systems and methods for conducting a reaction using electrowetting in a vertical or substantially vertical position. Some embodiments disclosed herein provide fluidic cartridges for use in a substantially vertical position comprising: (a) a front substrate; (b) a back substrate; (c) a droplet operations gap formed between the front substrate and the back substrate; and (d) a plurality of electrodes on the front substrate or the back substrate, wherein the plurality of electrodes are configured to transport a droplet along a substantially vertical plane defined by the front substrate and the back substrate.