Milliliter-to-microliter platform for on-demand loading of aqueous and non-aqueous droplets to digital microfluidics

We describe a world-to-chip interface for automated, on-demand loading of ~1μL droplets from a large (~1mL demonstrated) off-chip reservoir. Utilizing a combination of compressed inert gas and gravity to exert forces on the liquid, the technique employed is simple and robust, requiring no carrier fluid. Another key feature from a practical point-of-view is that all of the wetted parts are inexpensive and potentially disposable, thus avoiding cross-contamination in chemical and biochemical applications. The proof-of-concept and versatility of the platform are demonstrated with the loading of several aqueous and non-aqueous liquids on an electrowetting-on-dielectric microfluidic device.