A calorimetric determination of protein concentration for a picoliter (pL) liquid sample is proposed using a microfluidic calorimeter on a thermally isolated membrane. The concentration measurement of cytochrome c in a pL solution based on an AC calorimeter by the absorbance of a 532 nm diode laser is demonstrated to monitor the temperature change of the microchannel. The resolution of the concentration is defined by measuring the temperature change against various concentrations. In the case of the fabricated micro-calorimeter, the heat resistance of the isolated membrane is obtained as 1579 K/W. The composed heat resistance, including the support membrane and the solution in the channel, is obtained as 118 K/W. Although the heat loss is extensive, the resolution is calculated as 3.3 mM as a concentration sensor with 1.5 mol/K sensitivity. The calorimetric device has more potential to be used for detection of extremely small concentrations in liquid by optimizing the thermal isolation with a higher concentration resolution.
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