This work reports the demonstration of a thermopneumatic microfluidic actuator used to determine blood coagulation time. In this new system, the detection principle is the obstruction of a microfluidic channel by clotted blood. The sample actuation is done by aspiration due to air cooling in a cavity. We made a study of the position of the blood plug depending on the presence in the channel of coagulation reagent and observe a slowdown of the plug on a coated channel compared to a blank one.