Highly sensitive ac nanocalorimeter for microliter-scale liquids or biological samples

We developed an ultrasensitive ac nanocalorimeter for use with biological liquids by means of microfabrication technologies. The volume of the cell measurement is only 5 μL. This nanocalorimeter, tested on deionized water, allows the measurement of heat capacity variation above ±150 nJ/K (resolution of ±5×10−6) with an operating temperature ranging from −20 to 120 °C and a stability of 100 μK. Its use is demonstrated on diluted lysosyme solution measured at the frequency of 3 Hz. At 3 Hz, this ac calorimeter gives only the variation of the heat capacity during the denaturation, which allows complementary thermodynamic investigations as regards to classical differential scanning calorimetry measurements.