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Abstract：
Since different quantities of white blood cells (WBCs) in solution possess an adaptive osmotic pressure of cells, the WBCs themselves and in solution have similar concentrations, resulting in them having similar dielectric properties. Therefore, a microwave sensor could have difficulty in sensing the quantity variation when WBCs are in solution. This paper presents a highly sensitive, linear permittivity-inspired microwave biosensor for WBCs, counting through the evaporation method. Such a measurement method is proposed to record measurements after the cell solution is dripped onto the chip and is completely evaporated naturally. The proposed biosensor consists of an air-bridged asymmetric differential inductor and a centrally located circular fork-finger capacitor fabricated on a GaAs substrate using integrated passive fabrication technology. It is optimized to feature a larger sensitive area and improved Q-factor, which increases the effective area of interaction between cells and the electromagnetic field and facilitates the detection of their changes in number. The sensing relies on the dielectric properties of the cells and the change in the dielectric constant for different concentrations, and the change in resonance properties, which mainly represents the frequency shift, corresponds to the macroscopic change in the concentration of the cells. The microwave biosensors are used to measure biological samples with concentrations ranging from 0.25 × 106 to 8 × 106 cells per mL in a temperature (26.00 ± 0.40 °C) and humidity (54.40 ± 3.90 RH%) environment. The measurement results show a high sensitivity of 25.06 Hz/cells·mL-1 with a highly linear response of r2 = 0.99748. In addition, a mathematical modeling of individual cells in suspension is performed to estimate the dielectric constant of individual cells and further explain the working mechanism of the proposed microwave biosensor.
摘要：
由于溶液中不同数量的白细胞（WBC）具有细胞的适应性渗透压，WBC本身和溶液中的浓度相似，导致它们具有相似的介电性能。因此,当WBC在溶液中时，微波传感器可能难以感测数量变化。本文提出了一种高度敏感的，用于WBC的线性介电常数启发微波生物传感器，通过蒸发法计数。提出了这种测量方法以记录细胞溶液滴落到芯片上并自然完全蒸发之后的测量结果。拟议的生物传感器由使用集成无源制造技术在GaAs衬底上制造的空气桥接非对称差分电感器和位于中心的圆形叉指电容器组成。它被优化为具有更大的敏感区域和改进的Q因子，这增加了细胞与电磁场之间相互作用的有效面积，并有助于检测它们的数量变化。传感依赖于细胞的介电特性和不同浓度的介电常数的变化，以及共振特性的变化，主要代表频率偏移，对应于细胞浓度的宏观变化。微波生物传感器用于在温度（26.00±0.40°C）和湿度（54.40±3.90RH％）环境中测量浓度为0.25×106至8×106个细胞/mL的生物样品。测量结果表明，高灵敏度为25.06Hz/cells·mL-1，高度线性响应为r2=0.99748。此外,对悬浮中的单个细胞进行数学建模，以估计单个细胞的介电常数，并进一步解释所提出的微波生物传感器的工作机理。
