本研究是利用量測電流的方式，進而推算出紙張的孔隙率。離子溶液在紙張中流動時，因為纖維的阻擋，通量較沒有纖維的管道低，使得量測電流較小，我們藉由此概念作進一步的研究。為了降低蒸發量並且使管道壁面一致，我們利用兩片聚二甲基矽氧烷(PDMS)夾住紙管道，再用雙面膠固定，進行量測電流的實驗。除此之外，我們改變量測電壓、使用的溶液、管道尺寸，分析不同條件下的量測結果。由實驗結果可知，不同電壓下所測得的孔隙率變動不大，因此，此方法也可用於較低的工作電壓。使用氯化鉀、氯化鈉進行量測，都能得到相近的實驗結果，由此可推論出強電解質可用於此量測方法。改變管道的尺寸，依然不會對量測結果造成太大的影響，可以選擇體積較小的紙張進行量測。此研究提供一個新的紙張孔隙率量測法，在選擇紙基微流體晶片的材質時，能夠由此方法得到一個參考依據。

In this research, we measured the electric current in a paper channel to estimate the porosity of paper. When ions flow in a paper channel, the fibers in the paper obstruct the flow. Therefore, channels with fibers have lower flux and lower current because the volumetric flow rate in a paper channel with fibers is lower than that of a hollow channel (without fibers). Based on this concept, we conducted the following study. In order to reduce the evaporation effect and create the same channel surface, we used two pieces of polydimethylsiloxane (PDMS) to sandwich the paper channel and fixed them together with double-sided tape. In addition, we changed the applied voltage, solution, and the size of the channels to analyze the experimental results under different conditions. It was found from the experimental results that the measured porosity of the paper wasn’t changed significantly at different applied voltages. Therefore, this method can be carried out at a low voltage. Similar results can be obtained using potassium chloride (KCl) and sodium chloride (NaCl) to measure the porosity of paper. This infers that a strong electrolyte can be used in this method. Changing the size of the channels didn’t affect the experiment results, so a lower volume of paper can be used to measure porosity. This research offers a new method to measure the porosity of paper. This method can serve as a reference when choosing the material for use in microfluidic paper-based devices (μPADs).

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