05. Micro- and Nano-Scale Transport, MEMS

The thermal conductivity of liquids is dispensable for the design and analysis of thermal devices. The 3-omega method is one of the suitable tools to measure the thermal conductivity of liquids. There are many past reports on the measurement of the thermal conductivity of liquids using the 3-omega method. In conventional 3-omega methods, substrates with low thermal conductivity such as glass are used, however, it has some drawbacks. For instance, joule heat generated at the heater escapes to the substrate in case the thermal conductivity of a glass substrate is larger than that of liquid, which causes a decrease in the output signal. Second, when measuring with conductive liquids on the 3-omega sensor, adding an insulation layer between conductive liquids and the sensor is necessary. However, the fabrication process becomes complicated by adding an insulation layer, and measurement sensitivity is decreased due to an additional insulation layer. In this research, we demonstrate a new 3-omega sensor whose substrate is a thin and insulative parylene film to overcome drawbacks of conventional 3-omega sensors. To fabricate a device with thin parylene substrate, we developed new fabrication process. A thermal peeling film is used as a supporting substrate during device fabrication and thin parylene film is peeled off by heating the thermal peeling film after completing device fabrication. We confirmed that measurement sensitivity is increased by using thinner parylene substrate devices. Thermal conductivities of water, alcohol, and their mixtures were successfully measured by flexible 3-omega sensors on the submicron-thickness parylene film, and measured thermal conductivities are matched with literature values within 7 %.

Prof.

Toshiyuki Tsuchiya