磁感應式生乳品質檢測晶片

Magnetic Induced MEMS Biochip for Quality Inspection of Raw Milk

李瑋晨(Wei-Chen Li) ； 鄒慶福(Ching-Fu Tsou)

《科儀新知》 212期 (2017/09) Pp. 13-25

摘要

生乳中的體細胞數（Somatic cell count, SCC）目前在國際上被視為生乳等級評量的重要標準之一，其含量的多寡會直接影響生乳的價格、品質風味以及保存期限。因此，如何精確的檢測出生乳的體細胞數含量，對於酪農、生乳加工廠及消費者之間均具有相當重要的參考價值。有鑒於此，本研究提出一種磁感應式的生乳品質檢測晶片，其元件係利用微機電系統（MEMS）技術於矽基板上製作出兩個微型的共平面線圈，因此當施加一個特定頻率的交流訊號於激勵線圈時，由於待測物（生乳）感應的渦電流效應，便會造成感應線圈的輸出相位差產生變化，藉由上述的方式，便可直接量測生乳的體細胞數並達到及時檢測的功能。在本研究中，共平面雙線圈的磁感應特性及其感測效能，已分別利用模擬軟體COMSOL以及實驗的方式進行定性與定量的評估；此外，針對相同的生乳檢測樣本，也透過商用的體細胞數檢測儀進行量測，以作為檢測結果的對照數據。根據初步的實驗結果顯示，生乳的體細胞數含量越多，產生的相位差越大，兩者之間大約呈對數的變化關係；當施加9 MHz的激勵頻率在25環的線圈結構時，其量測靈敏度可達3°/log（SCC）。相較於現有的體細胞數檢測技術，本研究開發的雙線圈磁感應檢測晶片能夠有效的減少尺寸與降低成本，並能達到即時檢測之目的，使其具有較佳的生乳品質檢測效率。

並列摘要

In determining the degree of mastitic infection in raw milk, the somatic cell count (SCC) is the most widely accepted criterion that is used to quantify milk quality. A higher SCC can significantly reduce milk yield and increase treatment costs, so milk testing and quality control are essential if the milk processing industry is to protect raw milk from the risk of contamination by bacteria and other substances. For this, this article presents a novel inspection method that uses dual-coil inductance to evaluate the quality of raw milk. The device principally contains a silicon-based chip with two co-planar coils, which is fabricated using a simple microelectroplating process. When the coils are entirely immersed in raw milk and a specific alternating electrical signal is applied to one of the coils, the other coil induces a phase-shifted electrical signal because of the effect of eddy currents. Using the phase variation between both coils, the quality of the raw milk, in terms of the SCC (kcells/mL), can be evaluated. In this study, the characteristics of the magnetic inductance for a specified coil design and its sensing performance are simulated and evaluated using COMSOL software and by experiment. The experimental results show that higher SSCs cause larger phase shifts. This shift increases as the excitation frequency is increased. For a typical fabrication result, using a sensing coil with 25 loops, the measurement sensitivity in terms of SCC is 3°/log (SCC) at an excitation frequency of 9 MHz. The proposed dual-coil chip reduces size and cost and has a rapid response, which allows efficient quality inspection of raw milk.