Simultaneous thermal conductivity and diffusivity sensing in liquids using a micromachined device

Due to unique features like small thermal masses and reduced conductivities, membrane-based micromachined thermal sensors offer features 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 membrane and recording the resulting temperature at a specified distance using integrated germanium thermistors, the liquid's thermal parameters can be determined. A simple two-dimensional (2D) 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.