Self-priming microfluidic structures

A self-priming microfluidic junction, comprising:

• a first microfluidic channel comprising a floor and a ceiling, wherein a channel height is defined as a distance between the floor and ceiling;
• a channel height step in the floor, or ceiling, or both, wherein the channel height downstream of the channel height step is greater than the channel height upstream of the channel height step;
• an interior pillar positioned in the first microfluidic channel and extending from the floor to the ceiling, wherein the interior pillar comprises a widening portion at an upstream end of the interior pillar and a tapering portion at a downstream end of the interior pillar, wherein the interior pillar overlaps with channel height step such that the interior pillar is partially upstream of the channel height step and partially downstream of the channel height step;
• and
• a second microfluidic channel joining the first microfluidic channel at a capillary break opening in a wall of the first microfluidic channel, wherein the capillary break opening is positioned downstream of the channel height step, and wherein the capillary break opening has a height that is less than the channel height of the first microfluidic channel downstream of the channel height step.

A method of priming a microfluidic structure, comprising:

• providing a microfluidic channel comprising a floor and a ceiling, wherein a channel height is defined as a distance between the floor and the ceiling, wherein the channel height increases, in a fluid flow direction through the microfluidic channel, at a channel height step in the floor, or ceiling, or both, wherein an interior pillar is positioned in the microfluidic channel and extends from the floor to the ceiling, wherein the interior pillar comprises a widening portion at an upstream end of the interior pillar and a tapering portion at a downstream end of the interior pillar, wherein the interior pillar overlaps the channel height step such that the interior pillar is partially upstream of the channel height step and partially downstream of the channel height step;
• flowing a fluid through the microfluidic channel in the fluid flow direction by capillary action;
• and
• flowing the fluid past the interior pillar and the channel height step by capillary action.