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.