Flow control in microfluidic devices

1 . A microfluidic device comprising:

a device body defining a microfluidic pathway, the microfluidic pathway including:

a first channel,

a second channel downstream of the first channel, and

a junction including a transition between the first channel and the second channel, the transition to inhibit fluid entering the transition from the first channel from forming a meniscus across the second channel, thereby inhibiting capillary-driven flow into the second channel;

a valve that, when activated while capillary-driven flow of the fluid is inhibited at the transition, induces capillary-driven flow through the second channel by facilitating formation of the meniscus;

wherein the fluid entering the transition from the first channel is a first fluid,

the valve includes a plurality of valve channels defined by the device body, each of the plurality of valve channels in communication with the junction,

the valve is activated by providing one or more second fluids through the plurality of valve channels such that each of the one or more second fluids reach the junction, and

the meniscus is a combined meniscus formed by combination of the first fluid and each of the one or more second fluids at the junction, the valve facilitating formation of the combined meniscus by delivering each of the one or more second fluids to the junction.

2 . The microfluidic device of claim 1 , wherein:

the valve includes an inwardly deformable portion downstream of the transition,

the valve is activated by depressing and subsequently releasing the inwardly deformable portion, and

releasing the inwardly deformable portion induces a pressure reduction downstream of the transition, the pressure reduction to draw fluid from the first channel across the transition to form the meniscus.

3 . The microfluidic device of claim 1 , wherein:

the valve includes a valve portion upstream of the transition,

the valve is activated by manipulating the valve portion, and

manipulating the valve portion induces a pressure increase upstream of the junction, thereby pushing the fluid from the first channel across the transition to form the meniscus when the fluid is inhibited.

4 . The microfluidic device of claim 1 , wherein:

the valve includes a valve portion having an inner surface, and

the valve is activated by manipulating the valve portion while capillary-driven flow of the fluid is inhibited at the transition such that the inner surface contacts the fluid while the fluid is inhibited.

5 . The microfluidic device of claim 1 , wherein:

the device body is formed from a plurality of laminated layers,

the first channel is defined by a first set of layers of the plurality of laminated layers, and

the second channel is defined by a second set of layers of the plurality of laminated layers, the second set of layers having a greater cross-sectional area than the first set of layers.

6 . The microfluidic device of claim 1 , wherein:

the device body is formed from a plurality of laminated layers,

the first channel is defined by a first set of layers of the plurality of laminated layers,

the second channel is defined by a second set of layers of the plurality of laminated layers, and

the second set of layers is a proper superset of the first set of layers.

7 . The microfluidic device of claim 1 , wherein:

the device body is formed from a plurality of laminated layers,

the first channel is defined by a first set of layers of the plurality of laminated layers,

the valve includes a valve channel in communication with the junction and defined by a second set of layers of the plurality of laminated layers and in communication with the junction,

the fluid entering the transition from the first channel is a first fluid,

the valve is activated by providing a second fluid through the valve channel such that the second fluid reaches the junction and contacts the first fluid,

the meniscus is a combined meniscus formed by combination of the first fluid and the second fluid at the junction, the valve facilitating formation of the combined meniscus by delivering the second fluid to the junction, and

a portion of the valve channel immediately upstream of the junction extends parallel to a portion of the first channel immediately upstream of the junction.

8 . A microfluidic device comprising:

a device body formed from laminated layers, the laminated layers defining a microfluidic pathway, the microfluidic pathway including:

a first channel defined by a first set of layers of the laminated layers,

a second channel downstream of the first channel and defined by a second set of layers of the laminated layers, and

a junction including a transition between the first channel and the second channel, the transition to inhibit fluid entering the transition from the first channel from forming a meniscus across the second channel, thereby inhibiting capillary-driven flow into the second channel; and

a valve that, when activated while capillary-driven flow of the fluid is inhibited at the transition, induces capillary-driven flow through the second channel by facilitating formation of the meniscus;

wherein the fluid entering the transition from the first channel is a first fluid,

the valve includes a plurality of valve channels defined by the device body, each of the plurality of valve channels in communication with the junction,

the valve is activated by providing one or more second fluids through the plurality of valve channels such that each of the one or more second fluids reach the junction, and

the meniscus is a combined meniscus formed by combination of the first fluid and each of the one or more second fluids at the junction, the valve facilitating formation of the combined meniscus by delivering each of the one or more second fluids to the junction.

9 . The microfluidic device of claim 8 , wherein:

the plurality of valve channels in communication with the junction are defined by a third set of layers of the laminated layers and in communication with the junction.

10 . The microfluidic device of claim 8 , wherein the valve includes a deformable portion of the device body that, when at least one of depressed or released, induces a change in pressure along the microfluidic pathway such that the change in pressure results in the fluid being delivered into the second channel to form the meniscus when capillary-driven flow of the fluid is inhibited at the transition.