Feasibility study of noninvasive measurement of thermal conductivityand thermal diffusivity for biological materials

A noninvasive technique was developed to measure the thermophysical properties of biological materials. In this technique the temperature response of a material surface heated by CO₂ laser irradiation is measured with an infrared thermometry and compared with the theoretical response. The thermal conductivity and the thermal diffusivity are determined as the both values which yield the smallest deviation between the measured and analyzed temperature responses. The objective of the present study is to establish this technique by investigating the uncertainty of the method. An appropriate model of heat transfer is discussed first by taking into account of the effect of the laser absorption within the material and a heat loss from the material surface to the ambient. Then the accuracy of measurement is examined by using virtual experimental data with temperature fluctuation expected in an actual experiment. The virtual experimental data are generated by adding artificial fluctuation to a theoretical temperature response. The accuracy of measurement is estimated as a function of the standard deviation (S.D.) of the temperature fluctuation and the laser irradiation time. The effect of uncertainty in the absorption coefficient of the target material is also examined.