A micro-cantilever sensor for measuring fluid properties

A method of monitoring a reaction in, or a thermal property of, a fluid medium sample comprises providing at least one micro-cantilever sensor 300 further comprising at least two materials having different coefficients of thermal expansion and having a heater 310 and piezo-resistive sensor 320 integrated therein. The heater is pulsed with one or more electrical pulses to induce heat generation in the micro-cantilever and the output of the piezo-resistive sensor is used to characterize the response of the micro-cantilever to the changes in the fluid medium. A calibration response of the micro-cantilever is subtracted from the detected response. In a further embodiment a second micro-cantilever is used that includes a coating that causes or accelerates a reaction to be monitored in the fluid medium. The responses of the coated and uncoated cantilevers are then compared. Reactions may include binding, antibody-antigen or agglutination and thermal properties may include conductivity, temperature and heat capacity.