Apparatus and methods for multi-step channel emulsification

A device for forming droplets, the device comprising:

• a fluid supply channel;
• a collection chamber;
• and
• one or more nozzles disposed between the fluid supply channel and the collection chamber, wherein:
• each nozzle of the one or more nozzles comprises:
• an inlet portion;
• a first step;
• and
• a second step;
• the inlet portion has a channel height;
• the first step has a first step height and a first tread length;
• the first step height is greater than the channel height;
• the second step has a second step height and a second tread length;
• and
• the second step height is greater than the first step height.