A method of monitoring one or more specified reactions in a fluid medium sample using a thermal and mechanical signature, said method comprising: providing at least one calibrated micro-cantilever sensor having a calibrated micro-cantilever response characteristic, said micro-cantilever sensor comprising at least two materials having different coefficients of thermal expansion, and having a heater and piezo-resistive sensor integrated therein, said at least one calibrated micro-cantilever sensor being calibrated to thermal and mechanical changes, and a free end of said at least one micro-cantilever being operable to immerse into the fluid medium sample; pulsing the heater with one or more electrical pulses to induce heat generation in the micro-cantilever; sampling the output of the integrated piezo-resistive sensor to characterise a response of the micro-cantilever during the specified reaction in the fluid medium; and subtracting the calibrated micro-cantilever response characteristic from the sampled output to determine a characteristic of the one or more specified reactions in the fluid medium sample; wherein pulsing the heater with one or more electrical pulses to induce heat generation in the micro-cantilever causes sweeping of the micro-cantilever through a volume of the fluid medium sample; wherein providing at least one calibrated micro-cantilever sensor further comprises providing at least one calibrated micro-cantilever sensor having both a mechanical sensing mode and a thermal sensing mode; wherein the mechanical sensing mode senses changes to at least one physical property of the fluid medium sample by sensing damping of the sweeping of the micro-cantilever; wherein the thermal sensing mode senses changes to at least one thermal property of the fluid medium sample by sensing dissipation of heat into the surrounding fluid medium sample; and wherein the method further comprises tuning the at least one micro-cantilever to be more thermally sensitive, or more mechanically sensitive, on a sliding scale between the two, dependent on a test to be carried out on the fluid medium sample. providing at least one calibrated micro-cantilever sensor having a calibrated micro-cantilever response characteristic, said micro-cantilever sensor comprising at least two materials having different coefficients of thermal expansion, and having a heater and piezo-resistive sensor integrated therein, said at least one calibrated micro-cantilever sensor being calibrated to thermal and mechanical changes, and a free end of said at least one micro-cantilever being operable to immerse into the fluid medium sample; pulsing the heater with one or more electrical pulses to induce heat generation in the micro-cantilever; sampling the output of the integrated piezo-resistive sensor to characterise a response of the micro-cantilever during the specified reaction in the fluid medium; and subtracting the calibrated micro-cantilever response characteristic from the sampled output to determine a characteristic of the one or more specified reactions in the fluid medium sample; wherein pulsing the heater with one or more electrical pulses to induce heat generation in the micro-cantilever causes sweeping of the micro-cantilever through a volume of the fluid medium sample; wherein providing at least one calibrated micro-cantilever sensor further comprises providing at least one calibrated micro-cantilever sensor having both a mechanical sensing mode and a thermal sensing mode; wherein the mechanical sensing mode senses changes to at least one physical property of the fluid medium sample by sensing damping of the sweeping of the micro-cantilever; wherein the thermal sensing mode senses changes to at least one thermal property of the fluid medium sample by sensing dissipation of heat into the surrounding fluid medium sample; and wherein the method further comprises tuning the at least one micro-cantilever to be more thermally sensitive, or more mechanically sensitive, on a sliding scale between the two, dependent on a test to be carried out on the fluid medium sample.