Micro-beam sensor for detection of thermal conductivity of gases and liquids

•A new method for detecting thermal conductivity of liquids and gases was proposed.•The method provides a steady-state measurement that is unique for measuring fluid samples.•The principle of the method is simpler and more robust than previously proposed methods that use MEMS sensors.•Feasibility of the method was demonstrated by prototypes of the sensor.•The issues to be examined were pointed out for establishing the method.

A prototype of “micro-beam” MEMS sensor that is made of a thin metallic film suspended across a trench on a silicon substrate was fabricated for examination of the feasibility of detecting thermal conductivity of gases and liquids. Heating the sensor in a sample demonstrated the potential measurement at a steady state because no natural convection took place during heating. The measured temperature rise of the sensor agreed fairly well with the temperature rise estimated by a numerical analysis of heat conduction to a sample fluid from the sensor with given measured dimensions. The temperature of the sensor was significantly higher in the air than FC-72 as well, indicating the feasibility of detecting thermal conductivity by the proposed method.