Digital Microfluidic Cartridge Refractive Index Sensing with Waveguides

The patent introduces waveguide-based optical sensing as an intermediary between the droplet and the detection system. The waveguide serves as a mediator that guides light through the droplet in a controlled manner, eliminating stray light interference while maintaining optical sensing capability. The waveguide structure confines light within specific pathways, preventing unwanted light scattering that plagues free-space optics.

The patent replaces the mechanical free-space optical system with an integrated waveguide-based optical system. Instead of using free-space light paths that are susceptible to stray light, the system uses waveguides to confine and guide light through the droplet, substituting a more controlled optical mechanism that eliminates the harmful stray light effect.

The patent merges the optical sensing function directly into the microfluidic cartridge by integrating waveguides with the droplet manipulation structure. This consolidation eliminates the need for separate lenses, filters, and optical components that would otherwise be required to achieve stray light rejection. The waveguide structure itself performs the function of light confinement and guidance that would otherwise require multiple discrete optical elements.

The waveguide acts as an intermediary structure that is integrated directly into the cartridge, replacing the need for multiple external optical components. By incorporating the waveguide within the cartridge body, the system achieves precise optical measurement without requiring separate lenses, filters, or other optical elements, thereby reducing device complexity while maintaining measurement quality.