Characterizing Thermal Conductivity of Sub-Millimeter Biological Tissues Using Photothermal Shadowgraph Technique: Impact of Nanoparticle

The thermal conductivity of a biological tissue, which depends on the tissue’s molecular structure, provides crucial insights into its physiological function. Furthermore, various medical diagnostic and therapeutic strategies are based on the tissue’s thermal properties. Here, we have employed the photothermal shadowgraph technique, an optical method to measure the tissue’s thermal conductivity and diffusivity. In this regard, five distinct tissues extracted from three NMRI (Naval Medical Research Institute) male mice were examined. We investigated the quantitative impact of different nanoparticles present within the tissues on the thermal conductivity. The findings reveal a strong agreement between the measured values of the thermal conductivity and diffusivity obtained through the photothermal shadowgraph technique and those obtained using other methods. Additionally, the results indicate that Au, ZnO and CaCO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> significantly enhance the thermal conductivity of the tissues by 4, 2 and 2 times respectively. The TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> exhibited no discernible impact on the thermal conductivity of the tissue. Consequently, we can infer that the photothermal shadowgraph technique offers a contactless, quick, precise, and accurate method for determining the thermal properties of samples from biological tissues obviating the need for complicated instrumentations or a specific sample preparation procedure.