Koirala Gyan Raj, Dhakal Rajendra, Kim Eun-Seong, Yao Zhao, Kim Nam-Young
RFIC Lab, Department of Electronic Engineering, Kwangwoon University, 01897 Seoul, Korea.
Department of Computer Science and Engineering, Sejong University, 05006 Seoul, Korea.
Sensors (Basel). 2018 Apr 3;18(4):1075. doi: 10.3390/s18041075.
We present a microfabricated spiral-coupled passive resonator sensor realized through integrated passive device (IPD) technology for the sensitive detection and characterization of water-ethanol solutions. In order to validate the performance of the proposed device, we explicitly measured and analyzed the radio frequency (RF) characteristics of various water-ethanol solution compositions. The measured results showed a drift in the resonance frequency from 1.16 GHz for deionized (DI) water to 1.68 GHz for the solution containing 50% ethanol, whereas the rejection level given by the reflection coefficient decreased from -29.74 dB to -14.81 dB. The obtained limit of detection was 3.82% volume composition of ethanol in solution. The derived loaded capacitance was 21.76 pF for DI water, which gradually decreased to 8.70 pF for the 50% ethanol solution, and the corresponding relative permittivity of the solution decreased from 80.14 to 47.79. The dissipation factor increased with the concentration of ethanol in the solution. We demonstrated the reproducibility of the proposed sensor through iterative measures of the samples and the study of surface morphology. Successive measurement of different samples had no overlapping and had very minimum bias between RF characteristics for each measured sample. The surface profile for bare sensors was retained after the sample test, resulting a root mean square (RMS) value of 11.416 nm as compared to 10.902 nm for the bare test. The proposed sensor was shown to be a viable alternative to existing sensors for highly sensitive water-ethanol concentration detection.
我们展示了一种通过集成无源器件（IPD）技术实现的微纳加工螺旋耦合无源谐振器传感器，用于灵敏检测和表征水 - 乙醇溶液。为了验证所提出器件的性能，我们明确测量并分析了各种水 - 乙醇溶液成分的射频（RF）特性。测量结果表明，共振频率从去离子（DI）水的1.16 GHz漂移到含50%乙醇溶液的1.68 GHz，而反射系数给出的抑制水平从 -29.74 dB降至 -14.81 dB。获得的检测限为溶液中乙醇的体积组成为3.82%。对于去离子水，导出的负载电容为21.76 pF，对于50%乙醇溶液，该值逐渐降至8.70 pF，并且溶液的相应相对介电常数从80.14降至47.79。耗散因数随溶液中乙醇浓度的增加而增加。我们通过对样品的迭代测量和表面形态研究，展示了所提出传感器的可重复性。不同样品的连续测量没有重叠，并且每个测量样品的射频特性之间偏差极小。样品测试后，裸传感器的表面轮廓得以保留，与裸测试的10.902 nm相比，均方根（RMS）值为11.416 nm。所提出的传感器被证明是现有传感器用于高灵敏水 - 乙醇浓度检测的可行替代方案。
