Reusable bi-directional 3ω sensor to measure thermal conductivity of 100-μm thick biological tissues

• Published in: Review of scientific instruments 2015-01, Vol.86 (1), p.014905-014905
• Main Authors: Lubner, Sean D, Choi, Jeunghwan, Wehmeyer, Geoff, Waag, Bastian, Mishra, Vivek, Natesan, Harishankar, Bischof, John C, Dames, Chris
• Format: Article
• Language: English
• Subjects: Ablation; Animals; Biological properties; Computer Simulation; Electrical Equipment and Supplies; Error analysis; Heat conductivity; Heat transfer; Ice; Liver; Liver - chemistry; Mice; Models, Biological; Numerical methods; Scientific apparatus & instruments; Temperature; Thermal Conductivity; Tissues; Water; Water - chemistry
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.4905680

Accurate knowledge of the thermal conductivity (k) of biological tissues is important for cryopreservation, thermal ablation, and cryosurgery. Here, we adapt the 3ω method-widely used for rigid, inorganic solids-as a reusable sensor to measure k of soft biological samples two orders of magnitude thinner than conventional tissue characterization methods. Analytical and numerical studies quantify the error of the commonly used "boundary mismatch approximation" of the bi-directional 3ω geometry, confirm that the generalized slope method is exact in the low-frequency limit, and bound its error for finite frequencies. The bi-directional 3ω measurement device is validated using control experiments to within ±2% (liquid water, standard deviation) and ±5% (ice). Measurements of mouse liver cover a temperature ranging from -69 °C to +33 °C. The liver results are independent of sample thicknesses from 3 mm down to 100 μm and agree with available literature for non-mouse liver to within the measurement scatter.