Efficient dilution method, including washing method for immunoassay

An electrowetting on dielectric (EWOD) device comprising:

• a first shaping electrode that has a shape to shape a first droplet when activated;
• a second shaping electrode that has a shape to shape a second droplet when activated;
• and
• a bridging electrode which when activated joins the first droplet to the second droplet at an aggregate area of contact, wherein the electrodes are controlled in a manner so as to control the area of contact and the degree of mixing of the fluid between the first and second droplets.

A droplet manipulation device comprising:

• a plurality of electrode elements;
• and
• control circuitry configured to activate and de-activate the plurality of electrode elements to perform the steps of:
• activating the plurality of electrode elements to bring a first droplet into proximity of a second droplet;
• controlling the plurality of electrode elements to alter the shape of at least one of the first and second droplets;
• and
• further controlling the plurality of electrode elements to move at least one of the first or second droplets until the droplets are in contact about an aggregate area in a manner so as to control the area of contact and the degree of mixing of the fluid between the first and second droplets.