Droplet interfaces in electro-wetting devices

An electro-wetting device for taking measurements across a droplet interface, the electro-wetting device comprising:

• a first substrate supporting an array of actuation electrodes;
• an insulator layer covering the actuation electrodes and having a hydrophobic surf ace,
• a second substrate facing the hydrophobic surface of the insulator layer and supporting at least one set of at least two sensor electrodes, wherein the second substrate is coated by a hydrophobic material forming a further hydrophobic surf ace facing the hydrophobic surface of the insulator layer, the electro-wetting device being arranged to receive the fluid medium and the droplets disposed on the further hydrophobic surface of the hydrophobic material coating the second substrate, as well as the hydrophobic surf ace of the insulator layer, wherein the hydrophobic material coating the second substrate has apertures exposing at least part of the sensor electrodes,
• the electro-wetting device being arranged to receive a fluid medium and droplets comprising liquid in the fluid medium disposed on the hydrophobic surface, the actuation electrodes being configured to receive actuation signals for electro-wetting and moving received droplets in order to form at least one system of droplets having one or more droplet interfaces between droplets, and the sensor electrodes of each set being configured to make electrical connections to respective droplets in the at least one system of droplets.