Spatially variable hydrophobic layers for digital microfluidics

A digital microfluidic device, comprising:

• a substrate comprising a plurality of driving electrodes coupled to a set of thin-film-transistors, and a dielectric layer covering both the plurality of driving electrodes and the set of thin-film-transistors;
• a controller operatively coupled to the set of thin-film-transistors and configured to provide:
• a driving voltage to at least a portion of the plurality of driving electrodes;
• a first spatially variable wettability layer covering the dielectric layer comprising a first portion having a first contact angle, and a second portion having a second contact angle;
• a singular top electrode;
• a top hydrophobic layer covering the singular top electrode, wherein the top hydrophobic layer includes a second spatially variable wettability layer comprising a first portion having a first contact angle, and a second portion having a second contact angle;
• a spacer separating the variable wettability layer and the top hydrophobic layer creating a microfluidic region between the variable wettability and top hydrophobic layers, wherein the contact angles of the first and second variable wettability layers are the same along an axis perpendicular to the plane of the substrate comprising a plurality of driving electrodes.