High accuracy thermal conductivity measurement of aqueous cryoprotective agents and semi-rigid biological tissues using a microfabricated thermal sensor

Abstract

An improved thermal-needle approach for accurate and fast measurement of thermal conductivity of aqueous and soft biomaterials was developed using microfabricated thermal conductivity sensors. This microscopic measuring device was comprehensively characterized at temperatures from 0 °C to 40 °C. Despite the previous belief, system calibration constant was observed to be highly temperature-dependent. Dynamic thermal conductivity response during cooling (40 °C to –40 °C) was observed using the miniaturized single tip sensor for various concentrations of CPAs, i.e., glycerol, ethylene glycol and dimethyl sulfoxide. Chicken breast, chicken skin, porcine limb, and bovine liver were assayed to investigate the effect of anatomical heterogeneity on thermal conductivity using the arrayed multi-tip sensor at 20 °C. Experimental results revealed distinctive differences in localized thermal conductivity, which suggests the use of approximated or constant property values is expected to bring about results with largely inflated uncertainties when investigating bio-heat transfer mechanisms and/or performing sophisticated thermal modeling with complex biological tissues. Overall, the presented micro thermal sensor with automated data analysis algorithm is a promising approach for direct thermal conductivity measurement of aqueous solutions and soft biomaterials and is of great value to cryopreservation of tissues, hyperthermia or cryogenic, and other thermal-based clinical diagnostics and treatments.

Development of a Novel Electromagnetic Rewarming Technology for the Cryopreservation of Stem Cells with Large Volume

“…Thermal conductivity of sample solutions was measured using a micro thermal sensor developed by Liang, et al [38] and manufactured in the lab. The sensor works on the principle of Transient Hot Wire (THW).…”

Investigation of Electromagnetic Resonance Rewarming Enhanced by Magnetic Nanoparticles for Cryopreservation

“…Calibrations of temperature and heat flow were conducted before the Thermal Conductivity Assessment. The thermal conductivity measurement system for CPA solutions developed by Liang et al 26 consists of a digital multimeter (Keithley, Cleveland, OH, USA), a microfabricated thermal sensor, and a computer for data acquisition. The sensor works with the principle of a transient hot wire.…”

Thermographic Detection and Analysis of the Temporal and Spatial Evolution of Temperature upon Optical Heating of Gold Nanorod Assembly Immobilized in Agar

“…13,14 A microfabricated thermal sensor is capable of approaching a spatial resolution of 150 μm in semirigid biological tissues. 15 However, this invasive method is not suitable for measuring the temperature in a living body because of the penetration. It is also difficult to determine the exact temperature in space and in time simultaneously upon scanning detection positions.…”

“…Miscellaneous temporally and spatially resolved thermometric methods can be employed in nonfluidic matrixes of different physical dimensions and in diverse time domains, such as the transient plane source method and the transient hot-wire (THW) method on the 1–100 mm scale within 1–100 s . The THW method with thermocouples has been used to measure the thermal conductivity of tissue materials such as pig organs with the spatial domain in roughly mm. , A microfabricated thermal sensor is capable of approaching a spatial resolution of 150 μm in semirigid biological tissues . However, this invasive method is not suitable for measuring the temperature in a living body because of the penetration.…”