Methods and apparatus for controlling flow in a microfluidic arrangement, and a microfluidic arrangement

A microfluidic arrangement, comprising:

• a first liquid held predominantly by surface tension in a shape defining a microfluidic pattern on a surface of a substrate, the microfluidic pattern comprising at least an elongate conduit and a first reservoir;
• and
• a second liquid in direct contact with the first liquid and covering the microfluidic pattern, wherein:
• the microfluidic pattern and the depth and density of the second liquid are such that when a flow of liquid is driven through the elongate conduit into the first reservoir the first reservoir grows in volume, without either of the size and shape of an area of contact between the first reservoir and the substrate changing, until an upper portion of the first reservoir detaches from a lower portion of the first reservoir due to buoyancy and rises upwards through the second liquid, thereby allowing the first reservoir to continue to receive liquid from the flow of liquid without any change in the size and shape of the region of contact between the first reservoir and the substrate.

An apparatus for driving flow in a microfluidic arrangement, comprising:

• a microfluidic arrangement comprising a first liquid held predominantly by surface tension in a shape defining a microfluidic pattern on a surface of a substrate, the microfluidic pattern comprising at least an elongate conduit and a first reservoir;
• and a second liquid in direct contact with the first liquid and covering the microfluidic pattern;
• and
• a pumping mechanism comprising a delivery member having an internal lumen leading to a distal opening through which liquid can be delivered;
• and
• a control system configured to control the pumping mechanism to drive flow of liquid through the elongate conduit into the first reservoir by pumping liquid from outside of the microfluidic pattern into the microfluidic pattern via the distal opening, wherein:
• the microfluidic pattern and the depth and density of the second liquid are such that the first reservoir grows in volume during the flow of liquid into the first reservoir, without either of the size and shape of an area of contact between the first reservoir and the substrate changing, until an upper portion of the first reservoir detaches from a lower portion of the first reservoir due to buoyancy and rises upwards through the second liquid, thereby allowing the first reservoir to continue to receive liquid from the flow of liquid without any change in the size and shape of the area of contact between the first reservoir and the substrate.