Measurements of thermal properties and blood perfusion using the heat flux microsensor

A thin-film heat flux sensor was used in two transient conduction applications. First it was used in a device for simultaneously determining the thermal conductivity, κ, and the thermal diffusivity, α, of solid materials. The device was heated and then touched to metal samples at room temperature. The thermal properties were characterized based on the heat flux response of the gage, and the change in temperature of the metal surface at a specified distance away from the gage. A finite difference program was developed and used to model the system response. The effect of α was most evident by the time delay in the temperature response on the metal surface. The effect of κ was most evident in the heat flux response after the first few seconds of contact.

In the second application, the gage was used in a probe that was cooled and then touched to biological materials. A numerical model was used to demonstrate the effect of tissue blood perfusion on the surface heat flux. Experimental tests were performed on live dogs. Both the numerical model and the experiments showed that increases in blood perfusion could be detected from the transient heat flux measurements. In both applications, this research forms the basis for instrumentation which will be able to measure κ, α, and blood perfusion.