披覆醋酸纖維薄膜之電容式感測系統應用於土壤碳源酵素活性之檢測

Abstract

電容式感測器是電化學感測的方法之一，基於電極與液面之間的界面形成電容性質。電容式感測器具有成本低廉、反應快速、非侵入式、靈活性高的優點，但「絕緣性」極重要，若反應介面的絕緣不佳，將導致離子通透使感測系統短路或不穩定。網版印刷碳膠電極經常使用在電化學生物感測器系統中，其電路設計上彈性高，優點為成本低、製程簡單、一次性。現行土壤綜合能力檢測之研究利用綿狀條織物、木材、混合纖維、天然纖維等可降解材料，埋入土壤中進行長期性的降解試驗，透過機械應力的拉伸強度以及重量損失等，定義土壤的總體微生物量。為了簡化檢測土壤總體微生物量之量測方法，並且產生更有效率的量測模式，可以應用在各式理想實驗室條件下調配之溶液中，我們使用了電容式感測器並且結合網版印刷碳膠電極，藉由披覆醋酸纖維薄膜在量測點上作為降解材料，透過化學、酵素、化學加酵素的溶液中降解，並且實際在不同菌量的土壤中降解，得到電容響應和時間的關係，研究化學條件、碳循環酵素降解醋酸纖維薄膜的趨勢、速率等，研究薄膜降解後之電容響應與土壤碳源酵素的關聯性。我們提出了成熟的單層披覆薄膜製程，能夠維持一定的絕緣度，證實薄膜厚度53±2.23 μm 在Cap-sensor電容量測系統量測有效範圍內，且研究披覆薄膜的製程，藉由薄膜品質管理驗證披覆薄膜的穩定度高，經長期浸泡中性緩衝液中，薄膜在第35天電容值變化量0.04±0.03 %。後續在單純化學條件、化學加上酵素條件，將披覆醋酸纖維薄膜的網版印刷碳膠電極浸泡在溶液中，依時間間隔量測其電容響應。使用全反射傅立葉紅外光譜分析醋酸纖維薄膜經過時間的降解，C=O與C-O化性變化以及薄膜粗略性之厚度變化與電容響應的關係。最終展示在實際土壤中，先使用成熟的土壤微生物含量測定方法（二乙酸螢光素方法）驗證，且將披覆薄膜的網版印刷碳膠電極埋入不同菌量的土壤中，該電容式生物感測器測得的電容響應反應曲線有顯著差異，定義土壤總微生物量指標。本研究提出利用電容式感測器檢測土壤總微生物量，深入研究碳源酵素降解醋酸纖維薄膜的效力，相比於傳統有機質分解的檢測手法：使用拉伸應力、重量損失等方法測定分解袋、棉織物或木材，電容式感測器結合網版印刷碳膠電極披覆薄膜整合人機介面操作，使用者可以透過特定應用場景，切換適當的量測模組，並且即時讀取資料和匯出整理。因而達成即時、有效、快速且操作容易之感測器架構，對於土壤品質的評估和其他生物學方面具有研究潛力，不論是農業、環境監測或是生醫應用後續都是此項技術可以切入的場域。

The capacitive sensor is one of the methods of electrochemical sensing, based on the capacitive nature of the interface between the electrode and the liquid surface. Capacitive sensors have the advantages of low cost, fast response time, non-intrusive, and high flexibility. However, insulation is crucial that poor insulation of the response interface can lead to ion penetration, short circuit, or instability of the sensing system. Screen-printed carbon electrode are commonly used in electrochemical biosensor systems due to their high flexibility in circuit design and the advantages of low cost, simple and disposable process. In the current study, degradable materials such as cotton, wood, mixed fibers, and natural fibers are buried in the soil and subjected to long-term degradation tests to determine the total microbial load of the soil through mechanical stress, tensile strength, and weight loss. In order to simplify the method of measuring the microbial load of soil and to produce a more efficient measurement model that can be applied to various solutions prepared under ideal laboratory conditions. We used a capacitive sensor combined with screen-printed carbon electrode to study the relationship between capacitive response and time by coating cellulose acetate film as degradation material at the measurement points, degradation by chemical, enzymatic, and chemical plus enzymatic solutions, and actual degradation in soil with different amounts of bacteria to study the chemical conditions, the trend and the rate of degradation of cellulose acetate film by carbon cycle enzymes, and the relationship between capacitive response and soil carbon cycle enzymes after cellulose acetate film degradation. The correlation between the capacitive response and soil carbon source enzymes was studied. We propose a mature single-layer cellulose acetate film process that can maintain a certain degree of insulation and confirm that the film thickness of 53±2.23 μm is within the effective range of measurement by the Cap-sensor capacitance measurement system. 0.03 % at day 35 after long term immersion in neutral buffer solution. Subsequently, the screen-printing carbon electrode coated with cellulose acetate film were immersed in the solution under pure chemical conditions and chemical plus enzymatic conditions, and the capacitive response was measured according to the time interval, and the relationship between the degradation of cellulose acetate film over time. Attenuated total reflectance fourier transform infrared spectroscopy was used to analyze the relationship between the degradation of acetate films over time, changes in C=O and C-O chemical properties, and changes in thickness of film roughness and capacitive response. The capacitive biosensor measured significant differences in the response curves of capacitive response to define the total microbial load of the soil, which was verified in real soil using a well-established method for soil microbial content determination (fluorescein diacetate method), and the screen-printed carbon electrodes coated with cellulose acetate films were buried in soil with different bacterial load. This study proposes the use of capacitive sensors to detect the total microbial load of soil and to investigate the effectiveness of carbon source enzymes in degrading cellulose acetate films. Compared with the traditional methods of organic decomposition: using tensile stress, weight loss, etc. to determine the decomposition of bags, cotton fabrics or wood. The capacitive sensors combined with screen-printed carbon electrode coated cellulose acetate film integrate human-machine interface operation, allowing users to switch between the appropriate measurement modules, and to read and export data in real time. This results in a real-time, effective, fast and easy-to-use sensor architecture with research potential for soil quality assessment and other biology applications, whether in agriculture, environmental monitoring or biomedical applications.