Droplet microfluidics offers great potential toward high-throughput screening but is generally limited by the current tubing-based sample-to-droplet interface that induces large sample wastage, low scalability, and lengthy sample switching idle time. In response, we have developed a universal tubing-free sample-to-droplet interface within a nanodroplet microfluidic device that shows low sample wastage, high scalability, and minimal idle time. The dual interfaces in our device reduce the sample switching downtime via parallelized operation. Cross contamination was minimized with our high washing efficiency protocol. For demonstration, we used our dual sample-to-droplet interfaces and processed 44 FAM dye samples with scrambled orders.