Method and apparatus for forming multiple emulsions

A method comprising:

• flowing a first fluid stream exiting a first microfluidic channel in a first direction;
• flowing a second fluid stream contained within a second microfluidic channel in a direction substantially in the first direction, the second stream circumscribing the first stream upon exiting of the first fluid stream from the first microfluidic channel, the first microfluidic channel being disposed in the second microfluidic channel;
• flowing a third fluid stream within the second microfluidic channel in a second direction that is substantially opposed to the first direction;
• and
• altering the direction of flow of the third fluid stream to flow substantially in the first direction upon contact with the second fluid.

A method of packaging a species comprising:

• suspending a species in a first fluid;
• flowing the first fluid in a stream in a first direction;
• surrounding a portion of the first fluid with a portion of a second fluid upon contact of the first fluid stream with a second fluid stream flowing substantially in the first direction, the second fluid being substantially immiscible with the first fluid;
• introducing a third fluid stream flowing in a direction substantially opposed to the first direction;
• and
• altering the direction of flow of the third fluid stream to flow substantially in the first direction upon contact of the third fluid stream with the second fluid stream, the third fluid stream surrounding the second fluid stream upon contact;
• and
• forming multiple droplets of the first fluid wherein the droplets contain at least one of the species.

A method for forming droplets, comprising:

• flowing a first fluid in a first direction in a first microfluidic conduit having a first diameter;
• flowing a second fluid in substantially the first direction in a second microfluidic conduit having an end defining an exit opening, wherein the second microfluidic conduit is disposed in the first microfluidic conduit;
• expelling the second fluid, from the exit opening of the second conduit, into the first fluid in the first microfluidic conduit;
• surrounding the first and second fluids with a third fluid upon contact with a third fluid stream flowing in a second direction that is substantially opposed to the first direction;
• altering the direction of flow of the third fluid stream to flow substantially in the first direction upon contact with the first fluid;
• advancing the second fluid, surrounded by the first fluid, into a restriction under conditions in which droplets of the second fluid in the first fluid are formed within the restriction;
• and
• releasing the droplets of the second fluid carried in the first fluid from the restriction into a region of dimension larger than the restriction.