Bipolar electrochemistry for cargo-lifting in fluid channels

We report for the first time the vertical propulsion of conducting beads in liquid filled capillaries by bipolar electrochemistry. The beads, when exposed to an external electric field, act as bipolar electrodes showing hydroquinone oxidation on one side and proton reduction on the other side. The related asymmetric bubble generation occurring at the bottom part of the beads drives their motion. The characteristic features of the propulsion can be tuned by changing parameters such as the applied electric field or the capillary shape. Using a conical capillary, we show that a Yo-Yo type motion can be induced. The quite versatile concept can then be used for cargo-lifting and is of potential interest for microfluidic applications in LOC devices.