System and apparatus for injecting droplets in a microfluidic system

A microfluidic apparatus with a controlled system for delivering one or more release of a volume of a first fluid with one or more droplets of a second fluid comprising:

• a main channel, with a carrier fluid having a flow direction, the carrier fluid carrying one or more droplets of the second fluid immersed in the carrier fluid;
• an auxiliary channel, formed as a reservoir having a predefined closed volume, fluidly coupled to the main channel at two intersections wherein the auxiliary channel connects to:
• a first intersection via a first orifice configured to create a first fluid interface between the carrier fluid and the first fluid in the auxiliary channel;
• a second intersection downstream to the first intersection via a second orifice configured to create a second fluid interface between the carrier fluid and the first fluid;
• wherein a flow of the carrier fluid is configured to induce a difference of pressure between the first and second orifice generating a balance condition such that a meniscus of the second fluid interface is maintained in the auxiliary channel, at the vicinity of the second orifice;
• wherein a balance deviation, with regard to the balance condition, greater than a predefined threshold, triggers a release of a volume of the first fluid from the second fluid interface into the main channel, and
• wherein the microfluidic apparatus further comprises one or more further auxiliary channels, each formed as a further reservoir having a predefined closed volume, fluidly coupled to the main channel at two further intersections wherein the auxiliary channel connects to the main channel.

A method of releasing one or more droplets of a first fluid with one or more droplets of a second fluid within a microfluidic apparatus, the method comprising:

• providing a main channel carrying one or more droplets of the second fluid immersed in the carrier fluid,
• providing an auxiliary channel, formed as a reservoir having a predefined closed volume and comprising the first fluid, fluidly coupled to the main channel at two intersections, with a first intersection via a first orifice of the auxiliary channel configured to create a first fluid interface between the carrier fluid and the first fluid in the auxiliary channel, and with a second intersection downstream to the first intersection via a second orifice of the auxiliary channel configured to create a second fluid interface between the carrier fluid and the first fluid,
• imparting a flow of the carrier fluid into the main channel, inducing therefrom a difference of pressure between the first and second orifice generating a balance condition such that a meniscus of the second fluid interface is maintained in the auxiliary channel, at the vicinity of the second orifice,
• creating a balance deviation, with regard to the balance condition, greater than a predefined threshold, thereby triggering a release of a volume of the first fluid from the second interface into the main channel,
• wherein the balance deviation with regard the balance condition at the second fluid interface is generated by:
• at least one droplet of the second fluid passing in the main channel between the first intersection and the second intersection, thereby increasing the pressure drop and triggering a release of a volume of the first fluid from the second fluid interface, and/or an actuator allowing a release of a volume of the first fluid from the second fluid interface.