Methods for sampling a liquid flow are provided. The method includes supplying a continuous liquid flow from a continuous flow fluid input source to a surface along a first flow path. The method additionally includes sampling the continuous liquid flow by performing an electric field-based technique to split off a sample droplet from a portion of the liquid flow, whereby the sample droplet is distinct from the liquid flow and controllable independently of the liquid flow, wherein the electric field-based technique is performed by providing a set of electrodes on the surface and selectively biasing the set of electrodes, whereby the sample droplet is formed on one of the set of electrodes.