Differential microthermometry enables high-throughput calorimetry

Abstract

The assessment of heat capacity, or calorimetry, is critical to the development of fluids that will cool electrified processes and systems, such as computing infrastructure, data centres, and high-performance electric vehicle batteries. However, the throughput of conventional measurement approaches is limited by the need to quantify heat flux. Here, we present an approach that is independent of heat flux quantification, eliminating the intrinsic bottleneck in calorimetry and enabling high-accuracy, high-speed fluid screening. The principle is the measurement of an advective temperature bias introduced by a sample fluid vs. a reference fluid, flowing in parallel symmetric microchannels. This microthermometric approach is tested in non-insulated flow-through microfluidic channels, demonstrating heat-flux independence while enabling continuous heat capacity measurement of a fluid stream. We assessed performance by measuring the heat capacity of 35 pure liquids and gases, liquid mixtures, and nanofluids, exhibiting a broad range of viscosities (0.015–400 mPa s), thermal conductivities (0.02–0.6 W m⁻¹ K⁻¹), temperatures (5–120 °C), and pressures (1–70 bar). We achieve an accuracy of ±1.1%, matching that of the gold standard, with a throughput that exceeds the incumbent by two orders of magnitude (∼1 min vs. hours). This approach enables continuous and rapid screening in a high-throughput manner, enabling the accelerated discovery of energy-carrying fluids.