A microfluidic device for analysing a test liquid comprising: a sensor provided in a sensing chamber, the sensor comprising a membrane; a sensing chamber inlet and a sensing chamber outlet connecting to the sensing chamber for respectively passing liquid into and out of the sensing chamber, a sample input port (33, 92) in fluid communication with the inlet, for introducing a test liquid into the microfluidic device; a liquid collection channel downstream of the outlet; a flow path comprising the sample input port (33,92), the sensing chamber inlet, the sensing chamber, the sensing chamber outlet and the liquid collection channel, and wherein the sensing chamber inlet, sensing chamber and liquid collection channel are arranged such that displacing liquid from the liquid collection channel into the sensing chamber in turn displaces liquid from the sensing chamber into the sensing chamber inlet; a flow path interruption between the sensing chamber outlet and the liquid collection channel, wherein the microfluidic device is configured to be changeable from an inactive state, in which liquid is prevented by the flow path interruption from flowing into the liquid collection channel from upstream, to an active state in which the flow path between the sample input port (33, 92) and the liquid collection channel is completed; and a buffer liquid, filling from the sample input port (33, 92) to the flow path interruption such that the sensor is covered by liquid and unexposed to a gas or gas/liquid interface; wherein the device is configured such that following a change of the device into the active state, the capillary pressure at the liquid collection channel and the capillary pressure at the sample input port (33, 92) are balanced such that the buffer liquid does not freely drain out of the sensing chamber and one or more volumes of test liquid may be introduced, via a wet surface of the input port (33, 92), such that the capillary pressure at the input port (33, 92) is less than the capillary pressure at the liquid collection channel so as to draw the test liquid into the device and displace the buffer liquid into the liquid collection channel. a sensor provided in a sensing chamber, the sensor comprising a membrane; a sensing chamber inlet and a sensing chamber outlet connecting to the sensing chamber for respectively passing liquid into and out of the sensing chamber, a sample input port (33, 92) in fluid communication with the inlet, for introducing a test liquid into the microfluidic device; a liquid collection channel downstream of the outlet; a flow path comprising the sample input port (33,92), the sensing chamber inlet, the sensing chamber, the sensing chamber outlet and the liquid collection channel, and wherein the sensing chamber inlet, sensing chamber and liquid collection channel are arranged such that displacing liquid from the liquid collection channel into the sensing chamber in turn displaces liquid from the sensing chamber into the sensing chamber inlet; a flow path interruption between the sensing chamber outlet and the liquid collection channel, wherein the microfluidic device is configured to be changeable from an inactive state, in which liquid is prevented by the flow path interruption from flowing into the liquid collection channel from upstream, to an active state in which the flow path between the sample input port (33, 92) and the liquid collection channel is completed; and a buffer liquid, filling from the sample input port (33, 92) to the flow path interruption such that the sensor is covered by liquid and unexposed to a gas or gas/liquid interface; wherein the device is configured such that following a change of the device into the active state, the capillary pressure at the liquid collection channel and the capillary pressure at the sample input port (33, 92) are balanced such that the buffer liquid does not freely drain out of the sensing chamber and one or more volumes of test liquid may be introduced, via a wet surface of the input port (33, 92), such that the capillary pressure at the input port (33, 92) is less than the capillary pressure at the liquid collection channel so as to draw the test liquid into the device and displace the buffer liquid into the liquid collection channel.