Microfluidic devices are miniature fluidic devices dealing with small fluidic volumes, usually in the sub-milliliter range. Microfluidic devices typically have micromechanical structures (microchannels, microtracks, micropaths, microvalves and others) and employ various fluid-moving mechanisms, such as mechanical parts (e.g., micropumps) hydro-pneumatic devices/methods and electrically-based effects (electrophoretic, dielectrophoretic, electro-osmotic, electrowetting, opto-electrowetting, and variations of these effects as well as other effects).
For biomedical applications, some microfluidic devices are designed to conduct sample processing, including concentration, filtration, washing, dispensing, mixing, transport, sample splitting, sample lysing and other sample handling functions.
Exemplary microfluidic devices of the present application include digital fluidic cartridges comprising a top plate, usually made of plastic, which is coated with a conductive coating layer, two hydrophobic layers with tracks or paths of electrode in between, a dielectric coating and a printed circuit board (PCB) bottom. The space between the two hydrophobic layers can be filled with a filler fluid which is immiscible with the sample fluid. In some instances, the conductive coating layer comprises poly(3,4-ethylenedioxythiophene) (PEDOT). One or more ionenes are often added to the conductive coating layer to increase the solubility of PEDOT for deposition. One example is polystyrene sulfonic acid (PSS) or polystyrene sulfonate.