An immunoassay method for determining the presence of a target in a liquid sample, the method comprising: (a) introducing the liquid sample to a proximal portion of a capillary flow channel; (b) advancing the liquid sample at a first flow rate toward a distal portion of the capillary flow channel until at least a distal gas-liquid interface of the liquid sample contacts a conjugate disposed in dry form within the capillary flow channel, the conjugate comprising a binding agent having an affinity for the target; (c) subsequently, by increasing a gas pressure differential between a proximal gas-liquid interface of the liquid sample and the distal gas-liquid interface of the liquid sample, advancing the liquid sample at a second flow rate toward the distal portion of the capillary flow channel until at least the distal gas-liquid interface contacts a detection zone within the capillary flow channel, the detection zone comprising a second binding agent having an affinity for a complex comprising the conjugate and the target, the second flow rate being slower than the first flow rate; and (d) subsequently, by increasing the gas pressure differential between the proximal and distal gas-liquid interfaces of the liquid sample, advancing the liquid sample at a third flow rate toward the distal portion of the capillary flow channel until at least a majority of conjugate is bound to the second binding agent and/or has been advanced beyond the detection zone toward the distal end of the capillary flow channel; wherein any of the steps of "increasing a gas pressure differential" is performed by increasing a volume of gas in communication with the distal gas-liquid interface of the liquid sample, optionally wherein the capillary flow channel is disposed within a microfluidic device. (a) introducing the liquid sample to a proximal portion of a capillary flow channel; (b) advancing the liquid sample at a first flow rate toward a distal portion of the capillary flow channel until at least a distal gas-liquid interface of the liquid sample contacts a conjugate disposed in dry form within the capillary flow channel, the conjugate comprising a binding agent having an affinity for the target; (c) subsequently, by increasing a gas pressure differential between a proximal gas-liquid interface of the liquid sample and the distal gas-liquid interface of the liquid sample, advancing the liquid sample at a second flow rate toward the distal portion of the capillary flow channel until at least the distal gas-liquid interface contacts a detection zone within the capillary flow channel, the detection zone comprising a second binding agent having an affinity for a complex comprising the conjugate and the target, the second flow rate being slower than the first flow rate; and (d) subsequently, by increasing the gas pressure differential between the proximal and distal gas-liquid interfaces of the liquid sample, advancing the liquid sample at a third flow rate toward the distal portion of the capillary flow channel until at least a majority of conjugate is bound to the second binding agent and/or has been advanced beyond the detection zone toward the distal end of the capillary flow channel; wherein any of the steps of "increasing a gas pressure differential" is performed by increasing a volume of gas in communication with the distal gas-liquid interface of the liquid sample, optionally wherein the capillary flow channel is disposed within a microfluidic device.