Microfluidic valve

A microfluidic valve comprising:

• a first portion of a liquid conduit to contain a gas, the first portion including a sensor to detect a flow of a liquid;
• a second portion of a liquid conduit to contain the liquid;
• a constriction between the first portion and the second portion and across which a capillary meniscus is to form between the gas and the liquid, wherein the constriction is an interface where the liquid conduit undergoes dimensional changes from a larger flow passage to a smaller flow passage and the constriction includes:
• a first side wall parallel to a direction of the flow of the liquid,
• a second side wall parallel to the first side wall, and
• a pillar disposed within the liquid conduit at a location between the first side wall and the second side wall, wherein the pillar extends into the first portion of the liquid conduit;
• a drop jetting device within the second portion proximate to the constriction to open the microfluidic valve by breaking the capillary meniscus across the constriction, wherein the drop jetting device includes a resistive element;
• a controller to activate the drop jetting device based upon signals from the sensor to break the capillary meniscus across the constriction and in response to the break of the capillary meniscus, to provide continuous flow of the liquid to the first portion from the second portion of the liquid conduit;
• and
• a second constriction between the first portion and the second portion in parallel with the constriction.

A microfluidic valve comprising:

• a liquid conduit including a first portion to contain a gas, a second portion to contain a liquid, a first side wall parallel to a direction of flow of a liquid, and a second side wall parallel to the first side wall, wherein the liquid conduit includes a plurality of constrictions in series along a microfluidic conduit, each of the plurality of constrictions being sized such that a capillary meniscus forms at a gas-air interface existing at one of the constrictions and is an interface where the liquid conduit undergoes dimensional changes from a larger flow passage to a smaller flow passage, and wherein each of the constrictions is provided by a plurality of teeth disposed along the first side wall and along the second side wall and are disposed within the second portion of the liquid conduit;
• at least one drop jetting device positioned proximate to the plurality of constructions to break the capillary meniscus, wherein the drop jetting device includes a resistive element;
• a controller to activate the drop jetting device based upon signals from a sensor disposed within the microfluidic valve to break the capillary meniscus and in response to the break of the capillary meniscus, to provide continuous flow of the liquid to the first portion from the second portion of the liquid conduit;
• and
• a spout which forms a constriction and part of the second portion and provides an outlet of the second portion to the first portion, the spout having an end projecting into the interior of the first portion to locate the constrictionformed by the spout within the first portion, and wherein the at least one drop jetting device is disposed within a portion of the interior of the spout.