Removing the ceiling on droplet microfluidics

Abstract We developed an open channel droplet microfluidics system that autonomously generates droplets by utilizing competing hydrostatic and capillary pressure. With only our open channel PTFE device, pipettes, and commercially available carrier fluid, we produce hundreds of microliter droplets; tubing, electronics, or pumps are not required, making droplet technology feasible for research labs without external flow generators. Furthermore, we demonstrated conceptual applications that showcase the process of droplet generation, splitting, transport, incubation, mixing, and sorting in our system. Unlike conventional droplet microfluidics, the open nature of the device enables the use of physical tools such as tweezers and styli to directly access the system; with this, we developed a new method of droplet sorting and transfer that capitalizes on the Cheerios effect, the aggregation of buoyant objects along a liquid interface. Our open channel platform offers enhanced usability, direct access to the droplet contents, easy manufacturability, compact footprint, and high customizability.