Bridge-Based Microsensor for Determining the Thermal Properties of Liquids

Due to unique features like small thermal masses and reduced conductivities, miniaturized thermal sensors offer properties superior to those provided by comparable macroscopic measurement setups. In this contribution a micromachined device is applied to characterize the thermal transport properties of various liquids. By means of sinusoidal excitation of a heater structure placed on a micro-bridge, and recording the resulting temperature at a specified distance using integrated germanium thermistors also located on micro-bridges, the liquid’s thermal parameters can be determined. A simple two-dimensional analytical model allows to interpret the amplitude and the phase of the measured sinusoidal temperature variation, yielding both, the thermal conductivity and the diffusivity of the liquid.