自1980年代以後，全球平均氣溫每年皆異常上升，最主要原因便是每年大氣中的溫室氣體含量大幅增加，大氣中二氧化碳濃度逐年上升源自於化石燃料過量的使用而破壞了生態體系中的碳循環，使得地底岩層中大量封存的碳快速被帶至地表進入大氣中而來不及循環回地底中，因此碳捕捉系統(Carbon Capture and Storage system, CCS)應運而生，然而其運作成本相當高，因此近年來利用植物行自發性光合作用來固定二氧化碳的研究相當受矚目，其中微藻相較其他植物擁有更高的光合成效率以及生長速率，此外，微藻於固定二氧化碳後產生的生物質也可再次被利用作為生質燃料或是健康食品，被視為相當有潛力的二氧化碳減量技術。然而生物質的產量相當容易受到培養時的條件如溫度、光照、溶液酸鹼值等影響，因此若要達到最高二氧化碳捕捉效率，則需篩選出微藻的最適化生長環境。本研究設計數種微型電化學感測器，冀望能整合於微藻微型生物反應器中，觀察其生長時環境中的溶氧值以及pH值，並於培養槽的出入口處設置二氧化碳感測器，比較兩處濃度的差異得知微藻捕捉二樣化碳的多寡。
本研究使用FeCl3在銀表面反應生成Ag/AgCl薄膜結構當作參考電極，在連續20天的觀察中與商用參考電極的電位差異僅為-4.97 ±0.90 mV，在微型反應器中微藻僅需3 - 4天便可達到生長穩定期，因此20天的穩定足以用於微型反應器中的電化學檢測。
pH感測器使用氧化銥薄膜當作感測電極，根據溶液中氫離子濃度的不同而使感測電極與參考電極之間量測到不同電位差。使用氧化石墨烯當作電極保護層，可使pH電極達到長時間的穩定，保護層提供電極物理性的保護防止其遭受環境汙染，同時保有高度的導電性質而不影響量測，在其量測範圍(pH4 – pH7)內電壓與pH值具有高度的線性關係。
溶氧感測器使用金當作感測電極，藉由施加電壓來強迫電極表面溶氧還原成水，量測還原電流的大小來得知溶氧濃度，其中使用Nafion/PDMS的修飾可以提升溶氧電極的穩定度及壽命，其中Nafion當作電解質層，而PDMS薄膜的作用為隔開感測電極與感測環境並確保氧氣擴散暢通的氣體擴散層，在其量測範圍內(2 – 9 mg/L)內電流大小與溶氧濃度具有高度的線性關係。
二氧化碳感測器使用聚乙烯亞銨(PEI)薄膜當作選擇層來抓住氣態的二氧化碳，形成碳酸氫根並釋放出氫離子，參雜進下方的聚苯胺奈米纖維層(PANI nano fiber)中，再利用最下層之氧化銥薄膜來感測其表面氫離子濃度的變化，藉以回推二氧化碳的濃度。然而目前二氧化碳感測器尚無法進行實際感測，需做更進一步的分析與改進方可用於微藻二氧化碳捕捉能力的分析。

Since 1980s, the average of global temperature increased year by year due to burning lots of fossil fuel caused a huge amount of carbon dioxide emission. Carbon capture and storage system (CCS) was developed in order to decrease the amount of carbon dioxide in atmosphere, yet its operation cost was high. Therefore, we can utilize plants doing photosynthesis to absorb the carbon dioxide in atmosphere. Microalgae have greater photosynthesis efficiency and growing rate compared to other kinds of plants; meanwhile, carbon was the most element in microalgae composition and most of the carbon needed when it growing was absorbing carbon dioxide from the air. Therefore, microalgae has great potential for capturing carbon dioxide. Furthermore, biomass of microalgae can be made for other valuable products, such as biofuel or medicine. However, the growing environment influenced the pathway of microalgae’s metabolism, influencing the growth of microalgae. Therefore, the growing environment parameter of microalgae should be optimized in order to gain highest carbon dioxide capturing efficiency. In this research, few electrochemical sensors was developed to monitor the concentration of dissolved oxygen and pH value of the environment during microalgae growing. Dissolved carbon dioxide sensor was set to calculate the amount of carbon dioxide consumed by microalgae.
Ag/AgCl film electrode was used as reference electrode in electrochemical measuring system in this research. The potential of Ag/AgCl film was -4.97 ±0.90 mV in 20 days. Usually, microalgae achieved stationary phase in 3 to 4 days. Therefore, the Ag/AgCl film was stable enough for being reference electrode in micro-bioreactor.
Iridium oxide electrode was used as sensing electrode in pH sensor. The open circuit potential between iridium oxide electrode and reference electrode changed by the amount of hydrogen ion in solution. The stability could be enhanced by using graphene oxide as the protected layer to prevent it from contaminated by environment. The potential of the senor and pH vale have great linear relationship in the range of pH4 to pH7.
Gold electrode was used as dissolved oxygen sensor. By applying potential on gold, oxygen was forced to reduce to water. Therefore, the concentration of dissolved oxygen could be known by the reduce current. The stability could be enhanced by coating Nafion as electrolyte layer and coating PDMS as gas permeable layer. The amount of reduce current and the concentration of dissolved oxygen have great linear relationship in the range of 2 to 9 g DO/mL..
While carbon dioxide was absorbed by the polyethylenimine selective layer of the sensor, carbon became carbonic acid and released hydrogen ion which was latter doped in the polyaniline layer. The hydrogen ion doped in polyaniline layer was detect by the beneath iridium oxide electrode. However, the carbon dioxide sensor was not yet for on-chip detection. It needed more analysis and improvement in order to being functional.

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