Contact measurement of thermal conductivity and thermal diffusivity of solid materials: Experimental validation of feasibility with a prototype sensor

A contact method has been proposed for measuring thermal transport properties of solids including soft materials. The method has an advantage of potential utilization for in-situ measurement without preparing a sample specimen. A unique feature of the method is to prepare a shallow cavity around a film sensor for a layer of a gel that is used to eliminate the thermal contact resistance between the sensor and the sample. A prototype sensor, 3 mm in diameter, was fabricated on the surface of 0.16-mm thick glass substrate, and used with a 50-μm thick silicon rubber sheet as a spacer for the gel. The transient temperature rise of the sensor was determined from the electrical resistance after heating the sensor at a constant current. The thermal conductivity and the thermal diffusivity of a sample as well as the thickness of the gel layer were then determined from an iteratively obtained theoretical temperature rise that agreed with the measured temperature rise. The results obtained by the experiments with four different materials indicated that the thermal conductivity could be determined within 10% errors. The present study therefore demonstrated feasibility of the method, while improvement is still needed to reduce the error particularly in the thermal diffusivity.