High-throughput dynamic reagent delivery system

An apparatus for creating a droplet library via a microfluidic system, the apparatus comprising:

• (a) a carrier fluid channel having a carrier fluid flowing therein at an adjustable or predetermined flow rate;
• (b) a plurality of droplet dispensers, each of which is in fluid communication with the carrier fluid channel for dispensing the contents therein into the carrier fluid flowing in the carrier fluid channel, wherein each droplet dispenser comprises:
• (i) a supply of reagent fluid;
• and
• (ii) an outlet channel,
• wherein the outlet channel is in fluid communication with the carrier fluid channel for the transfer of an on-demand volume of reagent fluid from the droplet dispenser into the carrier fluid, thereby releasing a droplet, wherein the droplet dispensers are each disposed within an array structure, wherein passageways are formed between an exterior of the array structure and an exterior structure of the droplet dispensers, and wherein droplets are released from the droplet dispensers in a direction perpendicular to the flow of the fluid flowing in the carrier fluid channel;
• (c) two or more controlled actuators, wherein each controlled actuator is connected to a droplet dispenser, and wherein activation of the two or more controlled actuators releases distinct species of reagent droplets from the droplet dispensers;
• (d) a focusing channel, wherein the focusing channel and the outlet channel of each droplet dispenser are in fluid communication, and wherein the focusing channel is configured to group the reagent droplets into a set of droplets;
• (e) a microfluidic cross-channel, wherein the microfluidic cross-channel and the focusing channel are in fluid communication at a ‘T’ junction, and wherein the microfluidic cross-channel comprises an emulsion droplet upstream of the junction;
• (f) a detector for detecting the emulsion droplet, wherein the detector is disposed in the microfluidic cross-channel and upstream of the junction, wherein the detector is in electronic communication with the two or more controlled actuators, and wherein the emulsion droplet is larger than the reagent droplets;
• and
• (g) a feedback control system for coordinating activation of the two or more controlled actuators upon detection of the emulsion droplet by the detector so that arrival of the set of droplets at the junction coincides with arrival of the emulsion droplet at the junction such that the set of droplets arrives at the junction behind the target droplet and, due to their smaller size, catch up to the larger droplet prior to arrival at a merging feature disposed downstream of the junction for merging the set of droplets with the emulsion droplet.