Bhattacharya Ranajoy, Cornell Ken, Browning Jim
Department of Electrical and Computer Engineering, Boise State University, Boise, ID 83725, USA.
Department of Chemistry and Biochemistry, Boise State University, Boise, ID 83725, USA.
Appl Sci (Basel). 2024 Jun 1;14(11). doi: 10.3390/app14114342. Epub 2024 May 21.
This paper describes the principles behind the radio-frequency (RF) sensing of bacterial biofilms in pipes and heat exchangers in a dairy processing plant using an electromagnetic simulation. Biofilm formation in dairy processing plants is a common issue where the absence of timely detection and subsequent cleaning can cause serious illness. Biofilms are known for causing health issues and cleaning requires a large volume of water and harsh chemicals. In this work, milk transportation pipes are considered circular waveguides, and pasteurizers/heat exchangers are considered resonant cavities. Simulations were carried out using the CST studio suite high-frequency solver to determine the effectiveness of the real-time RF sensing. The respective dielectric constants and loss tangents were applied to milk and biofilm. In our simulation, it was observed that a 1 μm thick layer of biofilm in a milk-filled pipe shifted the reflection coefficient of a 10.16 cm diameter stainless steel circular waveguide from 0.229 GHz to 0.19 GHz. Further sensitivity analysis revealed a shift in frequency from 0.8 GHz to 1.2 GHz for a film thickness of 5 μm to 10 μm with the highest wave reflection (S11) peak of ≈-120 dB for a 6 μm thick biofilm. A dielectric patch antenna to launch the waves into the waveguide through a dielectric window was also designed and simulated. Simulation using the antenna demonstrated a similar S11 response, where a shift in reflection coefficient from 0.229 GHz to 0.19 GHz was observed for a 1 μm thick biofilm. For the case of the resonant cavity, the same antenna approach was used to excite the modes in a 0.751 m × 0.321 m × 170 m rectangular cavity with heat exchange fins and filled with milk and biofilm. The simulated resonance frequency shifted from 1.52 GHz to 1.54 GHz, for a film thickness varying from 1 μm to 10 μm. This result demonstrated the sensitivity of the microwave detection method. Overall, these results suggest that microwave sensing has promise in the rapid, non-invasive, and real-time detection of biofilm formation in dairy processing plants.
本文描述了利用电磁模拟对乳制品加工厂管道和热交换器中细菌生物膜进行射频（RF）传感的原理。乳制品加工厂中生物膜的形成是一个常见问题，若不能及时检测并随后进行清洁，可能会导致严重疾病。生物膜会引发健康问题，而清洁需要大量的水和刺激性化学物质。在这项工作中，牛奶输送管道被视为圆形波导，巴氏杀菌器/热交换器被视为谐振腔。使用CST工作室套件高频求解器进行模拟，以确定实时RF传感的有效性。将各自的介电常数和损耗角正切应用于牛奶和生物膜。在我们的模拟中，观察到在充满牛奶的管道中，1μm厚的生物膜层使直径为10.16cm的不锈钢圆形波导的反射系数从0.229GHz移至0.19GHz。进一步的灵敏度分析表明，对于5μm至10μm的膜厚度，频率从0.8GHz移至1.2GHz，对于6μm厚的生物膜，最高波反射（S11）峰值约为-120dB。还设计并模拟了一个介质贴片天线，用于通过介质窗口将波发射到波导中。使用该天线的模拟展示了类似的S11响应，对于1μm厚的生物膜，观察到反射系数从0.229GHz移至0.19GHz。对于谐振腔的情况，使用相同天线方法在一个0.751m×0.321m×170m的带有热交换翅片且充满牛奶和生物膜的矩形腔中激发模式。对于1μm至10μm变化的膜厚度，模拟的共振频率从1.52GHz移至1.54GHz。该结果证明了微波检测方法的灵敏度。总体而言，这些结果表明微波传感在乳制品加工厂生物膜形成的快速、非侵入式和实时检测方面具有前景。
