Fluid control in microfluidic devices

A microfluidic device, comprising:

• a microfluidic channel network comprising a microchannel configured to receive a liquid and a mechanical manipulation zone in fluidic communication with the microchannel, the mechanical manipulation zone comprising an upper wall and a lower wall disposed in opposition to one another and wherein a mechanical compression or decompression of one of the upper or lower walls with respect to the other of the upper and lower walls induces movement of a liquid if present in the microchannel;
• a first electrode disposed to contact liquid within the microchannel at a first location;
• a first electrically conductive lead extending from the first electrode to a first electrical contact disposed on the microfluidic device outside of the microfluidic channel network, the first electrically conductive lead comprising a first lead portion disposed within, or adjacent, the mechanical manipulation zone;
• a second electrode disposed to contact liquid within the microchannel at a second location spaced apart from the first location;
• a second electrically conductive lead extending from the second electrode to a second electrical contact disposed on the microfluidic device outside of the microfluidic channel network and spaced apart from the first electrical contact, the second electrically conductive lead comprising a second lead portion disposed within, or adjacent, the mechanical manipulation zone;
• wherein, the first and second electrodes are each configured to perform a respective liquid sensing or target detection function at the respective first and second location and a mechanical compression of one of the upper or lower walls with respect to the other of the upper and lower walls brings the first and second electrical contacts into electrical communication with one another and, if the first and second lead portions are in electrical communication with one another, a mechanical decompression of one of the upper or lower walls with respect to the other breaks the electrical communication between the first and second electrical contacts.

A method of operating a microfluidic device, comprising:

• placing the microfluidic device in an operative position with respect to a diagnostic reader, the microfluidic device comprising (a) a microfluidic channel network, the microfluidic network comprising an application zone, a microchannel configured to receive a liquid applied to the application zone, and a gas bladder in gaseous communication with the microchannel and (b) (i) a first electrical contact disposed on the microfluidic device outside of the microfluidic channel network and in electrical communication with a first lead portion disposed within or adjacent the gas bladder and a first liquid sensing electrode disposed to contact liquid within the microchannel at a first location and (ii) a second electrical contact disposed on the microfluidic device outside of the microfluidic channel network and in electrical communication with a second lead portion disposed within or adjacent the gas bladder and a second liquid sensing electrode disposed to contact liquid within the microchannel at a second location spaced apart from the first location, wherein the first and second electrical contacts are in electrical communication with one another when the gas bladder is in a fully compressed state;
• compressing a wall of the gas bladder until the gas bladder is in the fully compressed state with the first and second electrical contacts in electrical communication with one another;
• applying a liquid sample to an application zone of the microfluidic channel network;
• decompressing the wall of the gas bladder thereby moving the liquid sample within the microfluidic channel network;
• and
• after the step of decompressing the wall of the gas bladder, sensing the presence of the liquid sample at the first liquid sensing electrode by detecting a first electrical signal at the first electrical contact and sensing the presence of the liquid sample at the second liquid sensing location by detecting a second electrical signal at the second electrical contact.