Plug-in tubes allow tunable oil removal, droplet packing, and reaction incubation for time-controlled droplet-based assays

Here, we report a unique microfluidic technique that utilizes a membrane filter and plug-in tubes to remove oil and pack water-in-oil droplets for controlled incubation of droplet-based assays. This technique could be modularly incorporated into most droplet-generation devices without a need to alter the original designs. Our results show that removing excess oil to form tightly packed droplets allows for extended and controllable incubation for droplets traveling in microchannels. The efficiency of this technique was evaluated and confirmed using a time-dependent enzyme assay with a fluorometric readout. The system is also readily generalizable to control inter-droplet distance, crucial for studying droplet communication and pattern formation.

Automated summary

This unique microfluidic technique utilizes a membrane filter and plug-in tubes to remove oil and pack water-in-oil droplets for controlled incubation of droplet-based assays. The system allows for extended and controllable incubation of droplets in microchannels, and can be easily integrated into most droplet-generation devices without altering their original designs. Additionally, the technique is evaluated and confirmed to be efficient for time-dependent enzyme assays with a fluorometric readout, and can be generalized to control inter-droplet distance for studying droplet communication and pattern formation.