Abstract: A biosensor (10) for measuring changes in viscosity, density and/or mass in a fluid to be examined, for example a blood coagulation sensor or immunoassay system. According to the invention, the reagents necessary for the test are contained in a support (13) which is put onto the measurement surface (18) of a piezoelectric element (8). As a blood coagulation sensor, the measurement surface (18) may according to the invention itself have a coagulation activator action or else be coated with coagulation activators.

Abstract: A disposable biosensor for measuring changes in viscosity and/or density in a test fluid includes a disposable housing surrounding a measuring chamber. A piezoelectric element is disposed in the measuring chamber and constitutes an oscillating unit. The piezoelectric element has a measuring surface adapted to be wetted with a measuring mixture comprising the test fluid and a reaction component. The reaction component is disposed inside the measuring chamber in a vicinity of and not touching the measuring surface of the piezoelectric element before any test fluid is introduced into the measuring chamber. Access is provided in the disposable housing for introducing the test fluid into the measuring chamber so that the test fluid comes into contact with the reaction component and the measuring surface of the piezoelectric element upon its introduction into the measuring chamber.