Progressive techniques that enable reagent-free detection and analysis of low-concentration and low-volume chemical samples are of great interest for scientific and technological investigations in biochemical and physiological areas. Highly sensitive microwave-based sensors are promising approaches among such techniques. In this work, we present a novel microwave-based noncontact sensing method to determine the concentration of standard bovine serum albumin (BSA) solution. It is demonstrated that the modal suppression technique can excite a split-ring resonator by two independent microstrip lines with reversed phase, resulting in high quality factor and resolution. The quality factor exceeding 5.5×1055.5\times 10^{5} with lossy-liquid loaded can be achieved at ∼4.3\sim 4.3 GHz. The obtained high resolution in frequency is ∼20\sim 20 kHz for the concentration of BSA from 0 to 1 mg/mL. The measured concentration level ranges from 1 to 200 mg/mL in 0.9% sodium chloride, which covers most commercial standard BSA solutions. An equivalent circuit model is built to study and explain its working principle. Using the fit premeasurement data of standard solutions, the concentration and permittivity of an unknown BSA solution can be estimated.

中文翻译：

---

基于高 Q/高分辨率谐振器的牛血清白蛋白溶液微波测量


能够实现无试剂检测和低浓度、低体积化学样品分析的先进技术对于生化和生理领域的科学技术研究具有极大的意义。高灵敏度微波传感器是此类技术中最有前途的方法。在这项工作中，我们提出了一种新颖的基于微波的非接触式传感方法来测定标准牛血清白蛋白（BSA）溶液的浓度。结果表明，模态抑制技术可以通过两个独立的反相微带线激励开环谐振器，从而获得较高的品质因数和分辨率。在加载有损液体的情况下，可以在 ~4.3\sim 4.3 GHz 下实现超过 5.5×1055.5\times 10^{5} 的品质因数。对于 0 至 1 mg/mL 的 BSA 浓度，获得的高分辨率频率为 ∼20\sim 20 kHz。 0.9% 氯化钠中测量的浓度范围为 1 至 200 mg/mL，涵盖大多数商业标准 BSA 溶液。建立等效电路模型来研究和解释其工作原理。利用标准溶液的拟合预测数据，可以估计未知 BSA 溶液的浓度和介电常数。