A Dual-Mode Microwave Resonator for Liquid Chromatography Applications
A Dual-Mode Microwave Resonator for Liquid Chromatography Applications
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DOI：
10.1109/jsen.2020.3018683
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发表时间：
2021-01
影响因子：
4.3
通讯作者：
D. Ye;.. Omkar-Omkar-51447685;Pingshan Wang
中科院分区：
文献类型：
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作者：
D. Ye;.. Omkar-Omkar-51447685;Pingshan Wang
本文介绍了一种用于高效液相色谱（HPLC）的微波微流控传感器。该传感器基于改进的方形环负载谐振器（SRLR），其中传输线和环被电短路并产生中心间隙。微流控通道粘接在间隙上方，用于测试液体（LUT）测量。当LUT介电常数大于阈值时，谐振器的两个退化模式被分离，产生两个传输零频率。阈值介电常数可以很容易地通过间隙大小来调整。当LUT介电常数接近阈值时，灵敏度较高。这些特点使所提出的谐振器可以针对不同的微流体应用进行优化。为了验证设计，构建了三个间隙尺寸为$10~\mu \text{m}$、$30~\mu \text{m}$和$90~\mu \text{m}$的谐振器，并在不同体积分数的水-甲醇溶液中进行了测试。此外，该传感器与HPLC系统串联，用于咖啡因和蔗糖的检测。检测线性的特点是测量水-咖啡因样品从0.77 ppm到1000 ppm。达到了0.231 ppm的检测限（LOD），显示出与商用紫外线（UV）探测器相当的灵敏度。该传感器对梯度洗脱的兼容性也得到了证明。
This work presents a microwave microfluidic sensor for high performance liquid chromatography (HPLC) applications. The sensor is based on a modified square ring loaded resonator (SRLR), where a transmission line and a ring are electrically shorted with a center gap. A microfluidic channel is bonded above the gap for liquid-under-test (LUT) measurement. When the dielectric constant of LUT is above a threshold value, two degeneration modes of the resonator are separated, resulting in two transmission-zero frequencies. The threshold dielectric constant can be easily tuned by the gap size. High sensitivity is achieved when LUT dielectric constant is close to the threshold value. These features enable the proposed resonator to be optimized for different microfluidic applications. To validate the design, three resonators with $10~\mu \text{m}$ , $30~\mu \text{m}$ and $90~\mu \text{m}$ gap sizes are built and tested with water-methanol solutions in various volume fractions. Additionally, the sensor is connected in series with HPLC system for caffeine and sucrose detection. The detection linearity is characterized by measuring water-caffeine samples from 0.77 ppm to 1000 ppm. A 0.231 ppm limit of detection (LOD) is achieved, revealing a comparable sensitivity with commercial ultraviolet (UV) detectors. The compatibility of the proposed sensor to gradient elution is also demonstrated.