Digital Microfluidics - Implementation

Implementation

In one of various embodiments of EWOD-based microfluidic biochips, investigated first by Cytonix in 1987 and subsequently commercialized by Advanced Liquid Logic, there are two parallel glass plates, and the bottom plate contains a patterned array of individually controllable electrodes, and the top plate is coated with a continuous grounding electrode. A dielectric insulator coated with a hydrophobic is added to the plates to decrease the wettability of the surface and to add capacitance between the droplet and the control electrode. The droplet containing biochemical samples and the filler medium, such as the silicone oil, a fluorinated oil or air are sandwiched between the plates; the droplets travel inside the filler medium. In order to move a droplet, a control voltage is applied to an electrode adjacent to the droplet, and at the same time, the electrode just under the droplet is deactivated. By varying the electric potential along a linear array of electrodes, electrowetting can be used to move droplets along this line of electrodes.