Electrowetting Microdroplet Formation with ISFET Sensing

The dielectric layer is segmented into multiple regions with different surface properties (hydrophilic and hydrophobic regions). The hydrophilic regions act as trapping zones that capture portions of the bulk droplet, while the hydrophobic regions allow the droplet to move over. This segmentation enables efficient formation of multiple uniform microdroplets from a single bulk droplet by strategically distributing the trapped portions across the substrate.

Different regions of the dielectric layer are given different surface properties: hydrophilic regions with high surface energy to trap and hold liquid, and hydrophobic regions with low surface energy to allow movement. This local differentiation creates zones where the droplet is attracted to and retained, forming uniform microdroplets of predetermined volume based on the geometry and distribution of the hydrophilic regions.

The patent merges the EWOD droplet manipulation functionality with sensing capabilities by integrating ISFET sensors directly into the dielectric layer structure. The ISFET sensors are positioned within or adjacent to the hydrophilic regions, allowing simultaneous droplet movement and pH measurement. This integration enables accurate measurement of pH and DNA concentration in the microdroplets without requiring separate measurement devices, thereby reducing overall system complexity while improving measurement precision.

The dielectric layer structure serves multiple functions: it provides the electrowetting mechanism for droplet movement, defines the geometry for microdroplet formation through its hydrophilic/hydrophobic patterning, and houses the ISFET sensors for chemical measurement. This multi-functionality allows a single integrated structure to accomplish droplet manipulation and analytical measurement, improving measurement accuracy while avoiding the complexity of separate systems.

Instead of using complex three-dimensional structures or multiple separate components, the patent achieves precise microdroplet formation by applying different surface properties to different regions of the dielectric layer. The hydrophilic regions are created through surface treatment or material selection, while the hydrophobic regions provide contrast. This two-dimensional patterning of surface properties is simpler to manufacture than volumetric structuring while achieving the same microdroplet uniformity.

The patent controls microdroplet formation by adjusting surface energy parameters of the dielectric layer regions rather than changing the bulk material composition or adding complex mechanical components. By varying the surface energy (hydrophilic vs. hydrophobic) and the geometric parameters of the hydrophilic regions, precise control over microdroplet volume and uniformity is achieved through a relatively simple modification of surface properties rather than complex device architecture.