Methods and Apparatus for Flow-Controlled Wetting

A method of determining a first position at which a dispersed phase droplet wets a surface of a channel, the method comprising:

• (a) immersing the dispersed phase droplet in a continuous phase fluid, wherein the continuous phase fluid is immiscible with the dispersed phase droplet;
• (b) flowing the dispersed phase in the continuous phase through the channel at a dispersed phase droplet velocity, wherein the dispersed phase droplet is separated from the surface by a film of the continuous phase fluid having a film thickness;
• and
• (c) reducing the film thickness to rupture the film at the first position, wherein the droplet wets the surface at the first position.

A method of removing a first portion of a dispersed phase immersed in a continuous phase fluid, wherein the continuous phase fluid is immiscible with the dispersed phase, from a dispersed phase retaining chamber operably configured to retain the portion provided that the volume of the first portion is less than the volume of the chamber, the method comprising:

• a. immersing one or more dispersed phase droplets in the continuous phase fluid, to form a second portion of the dispersed phase;
• b. flowing the second portion of the dispersed phase into the dispersed phase retaining chamber, wherein the total volume of the dispersed phase portions exceeds the volume of the dispersed phase retaining chamber,
• c. contacting the first dispersed phase portion with the second dispersed phase portion for a period sufficient for the first dispersed portion and second dispersed phase portion to combine to form an elution stream encapsulated in the continuous phase fluid, and
• d. flowing the elution stream through a dispersed phase retaining chamber exit.

A process of treating a dispersed phase droplet in a microfluidic device, the process comprising:

• (a) immersing a first dispersed phase droplet in a continuous phase fluid, wherein the continuous phase fluid is immiscible with the first dispersed phase droplet, to form a first portion of a dispersed phase;
• (b) flowing the first dispersed phase droplet into a storage element of the device with a first dispersed phase droplet velocity, wherein the storage element comprises
• a main channel and a dispersed phase retaining chamber for receiving said dispersed phase droplet from the main channel, wherein the main channel is operably configured to reduce dispersed phase droplet velocity as said dispersed phase droplet approaches the retaining chamber, and wherein the retaining chamber is operably configured to retain said dispersed phase droplet within the storage element provided that the total volume of the dispersed phase within the retaining chamber is less than the volume of the retaining chamber,
• wherein the first dispersed phase droplet is separated from a surface of the storage element by a first film of the continuous phase fluid having a first film thickness;
• and
• (c) rupturing the first film at a first position within the storage element, wherein the first dispersed phase droplet wets the surface at the first position.

A microfluidic system for storing and processing dispersed phase droplets, the system comprising:

• (a) an array of at least two parallel independently addressable storage elements, wherein each storage element comprises:
• a main channel and a dispersed phase retaining chamber for receiving at least one of said dispersed phase droplets from the main channel, wherein the at least one of said dispersed phase droplets forms a portion of a dispersed phase within the storage element, and wherein the main channel is operably configured to reduce the velocity of the at least one of said dispersed phase droplets as the at least one of said dispersed phase droplets approaches the dispersed phase retaining chamber, and wherein the dispersed phase retaining chamber is operably configured to retain the at least one of said dispersed phase droplets within the storage element provided that the total volume of the dispersed phase within the dispersed phase retaining chamber is less than the volume of the retaining chamber;
• (b) an inlet channel shared by the at least two storage elements for flowing the at least one of said dispersed phase droplets to a selected storage element;
• and
• (c) an elution channel shared by the at least two storage elements for flowing the dispersed phase from the selected storage element.

A method of determining a first position at which a dispersed phase droplet wets a dispersed phase wetting surface of a microfluidic device, the wetting surface having a uniform wettability, the method comprising:

• (a) immersing the dispersed phase droplet in a continuous phase fluid, wherein the continuous phase fluid is immiscible with the dispersed phase droplet;
• (b) flowing the dispersed phase droplet immersed through the microfluidic device at a dispersed phase droplet velocity, wherein the dispersed phase droplet is separated from the surface of the conduit by a film of the carrier liquid having a film thickness;
• and
• (c) reducing the film thickness to rupture the film at the first position.