High-frequency temperature pulse-response behavior through a porous nanocomposite scaffold for measuring the uptake of biological fluids.

The measurement of biological fluid uptake into a scaffold sensor has been modeled by measuring the response of induced high-frequency temperature pulses. For this, a heat transport equation is used, developed from Extended Thermodynamics, also equivalent to Cattaneo's equation, as well as an effective thermal conductivity. The effective thermal conductivity is experimentally validated against data measurements of a carbon nanotube porous nanocomposite, embedded with silica nanoparticles. This nanocomposite serves also as the case study for the scaffold sensor. The uptake of the biological fluid in this scaffold sensor is equivalent to a change in the effective thermal conductivity, monitored by an increase of the interstitial volume fraction. By imposing a high-frequency temperature oscillation, the temperature response at the other end of the porous medium is calculated. Depending on the ratio of the relaxation time and the thermal diffusion time, the temperature response can be of oscillatory nature or of an exponential growth to an asymptotic limit. It is observed that an observed phase lag in the temperature response indicates a change in the effective thermal conductivity and thus is a criterion denoting the amount of uptake.