Microfabricated thermal conductivity sensor: a high resolution tool for quantitative thermal property measurement of biomaterials and solutions
Microfabricated thermal conductivity sensor: a high resolution tool for quantitative thermal property measurement of biomaterials and solutions
复制标题
微加工热导率传感器：用于定量测量生物材料和溶液热性能的高分辨率工具
DOI：
10.1007/s10544-011-9561-3
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发表时间：
2011-10-01
影响因子：
2.8
通讯作者：
Gao, Dayong
中科院分区：
文献类型：
--
作者：
Liang, Xin M.;Ding, Weiping;Gao, Dayong
准确获取生物材料的热性能在低温生物学领域具有重要意义。目前，热针是唯一可用的能够测量生物材料热导率的设备，它是通过在金属护套中包裹一层绝缘涂层的手工缠绕的细金属线来构建的。主要缺点，如大尺度传感器尺寸，缺乏通用格式以适应各种形状和尺寸的样品，忽略了探头内部传热和传感元件与探头体之间的热接触电阻的影响，难以批量生产，数据可重复性和可靠性差，传感器校准劳动强度大，已经大大降低了它们作为提供生物标本关键热性能信息的基本测量工具的潜力。在这项研究中，我们描述了一种使用基于MEMS的概念验证热探头测量液体和软生物组织导热系数的方法的发展。通过采用微制造紧密包裹的金线作为加热器和热敏电阻，所介绍的热传感器可用于测量流体和天然软生物材料的导热性（特别是，传感器可直接插入活体动物/植物体内的软组织或与动物/植物体分离的组织中），而其他更标准的方法无法使用。使用热标准材料在室温下对两个随机选择的热探针进行校准。所得到的系统校准常数之间的差异小于10%。通过结合之前得到的系统校准常数，我们成功地利用随机选择的三个热探针测量了不同温度下不同溶液和组织样品的热导率。总体而言，测量值与推荐值一致（百分比误差小于5%）。与传统的宏观热传感器相比，微制造热导传感器具有更优越的特性，例如(a)降低了热质量和热电阻，(b)改善了传感器与样品之间的热接触，(c)易于批量生产，(d)可灵活地重新配置传感器几何形状以测量各种尺寸和形状的样品。(e)减少了同一批次微加工的所有传感器的校准工作量。基于MEMS的热导传感器是一种很有前途的方法，可以克服现有宏观器件的固有局限性，并能够提供各种形状和尺寸的生物材料的精确热导测量。
Obtaining accurate thermal properties of biomaterials plays an important role in the field of cryobiology. Currently, thermal needle, which is constructed by enclosing a manually winded thin metal wire with an insulation coating in a metallic sheath, is the only available device that is capable of measuring thermal conductivity of biomaterials. Major drawbacks, such as macroscale sensor size, lack of versatile format to accommodate samples with various shapes and sizes, neglected effects of heat transfer inside the probe and thermal contact resistance between the sensing element and the probe body, difficult to mass produce, poor data repeatability and reliability and labor-intense sensor calibration, have significantly reduced their potential to be an essential measurement tool to provide key thermal property information of biological specimens. In this study, we describe the development of an approach to measure thermal conductivity of liquids and soft bio-tissues using a proof-of-concept MEMS based thermal probe. By employing a microfabricated closely-packed gold wire to function as the heater and the thermistor, the presented thermal sensor can be used to measure thermal conductivities of fluids and natural soft biomaterials (particularly, the sensor may be directly inserted into soft tissues in living animal/plant bodies or into tissues isolated from the animal/plant bodies), where other more standard approaches cannot be used. Thermal standard materials have been used to calibrate two randomly selected thermal probes at room temperature. Variation between the obtained system calibration constants is less than 10%. By incorporating the previously obtained system calibration constant, three randomly selected thermal probes have been successfully utilized to measure the thermal conductivities of various solutions and tissue samples under different temperatures. Overall, the measurements are in agreement with the recommended values (percentage error less than 5%). The microfabricated thermal conductivity sensor offers superior characteristics compared to those traditional macroscopic thermal sensors, such as, (a) reduced thermal mass and thermal resistivity, (b) improved thermal contact between sensor and sample, (c) easy to manufacture with mass production capability, (d) flexibility to reconfigure sensor geometries for measuring samples with various sizes and shapes, and (e) reduced calibration workload for all sensors microfabricated from the same batch. The MEMS based thermal conductivity sensor is a promising approach to overcome the inherent limitations of existing macroscopic devices and capable of delivering accurate thermal conductivity measurement of biomaterials with various shapes and sizes.