Chip calorimeter for thermal characterization of bio-chemical solutions

Abstract

A chip calorimeter to measure thermal properties of bio-chemical fluid samples is successfully demonstrated. The chip calorimeter design enables the simultaneous measurement of thermal conductivity and thermal diffusivity of 2.5 μl liquid samples with high-sensitivity and high-throughput. The micro-calorimeter consists of two silicon nitride membranes, with integrated heaters and thermopiles that are 300 μm apart and enclose the liquid chamber. The sensor shows 5 V/W sensitivity and 200 K/W thermal resistance for water. The applicability of the micro-calorimeter to bio-chemical fluids thermal characterization is demonstrated by measuring thermal conductivity and thermal diffusivity of methanol–water mixtures and protein aqueous solutions (bovine serum albumin, BSA). Methanol–water mixtures thermal properties reveal good agreement with earlier reported experimental and theoretical data, showing approximately 2% deviation. Thermal properties of BSA solutions with concentrations up to 20% (w/v) were measured and values for thermal conductivity and diffusivity of (pure) BSA were estimated to be 0.20 W/Km and 0.64 × 10 −7 m 2/s, respectively. The fluidic chip-calorimeter resolves thermal properties for concentrations down to 1% of both methanol and BSA.