傳統力量感測器多使用剛性材料製成，使用上易有疲勞、破裂等問題產生，本研究使用聚二甲基矽氧烷(Polydimethylsiloxane, PDMS)為基材製作微流道裝置，其可撓性相較於剛性材料能有較大的適用範圍。實驗原理為使用推拉力計施壓於一儲存槽上方的PDMS表面，儲存槽內的流體將會往微流道流動，藉由記錄期間液體的位移或是電容的改變，製作出一施力與輸出的校正曲線。為先驗證實驗可行性，先使用直流道裝置測試其是否可隨外力改變而有相對應的液體介面位移，但因直流道內的流體只有一個方向可流動，無法正確判斷外力方向，僅能進行正向力量測實驗，故另設計十字流道，使裝置能感測側向力施力的大小及方向且更接近實際應用。
本研究以兩種不同的實驗原理進行量測，其一為光學式量測法，另一為非光學式量測法。在光學式量測法中使用PFPE油與去離子水作為工作流體與內部流體，並於相關實驗中確認了當十字流道在相同施力條件下，不會因施力方向與對應的流道分支不同而有不同趨勢的結果。在非光學實驗方法中使用鎵銦共晶體與空氣作為工作流體與內部流體，在此實驗中測試初始電容值對結果的影響以及後續設計四種電極的比較。結果顯示電容初始值並不會影響相同外力下電容變化的程度，四種電極設計則以平行電極反應最佳，其與靈敏度第二高之交指狀電極反應差約44.39%。在十字流道之正向力實驗中，其四分支之電容變化程度相同，在外力為2 N時電容變化量約為1.5 nF。側向力於十字流道中一流道平行方向施加時，其四分支對應之電容變化程度依大小分為三型態，當外力為2 N時其最大與次大之電容變化量相差54%，最大與最小則差95.8%。側向力於十字型流道45度方向施加時，四分支之電容變化程度分為兩型態，與施加力量方向相同的流道有較大的電容改變，相反方向則有較小的改變量，兩者變化程度相差26.04%，由此可得該微流道裝置可辨別施力方向。在實際應用層面，將直流道裝置固定於機械夾爪前端，透過實驗所得之校正曲線推測未知外力的大小。在研究的最後使用磁性流體，利用其可隨外加磁場改變性值的特性，達到改變適用外力量測範圍之目的，透過比較發現磁場的有無使裝置在0~3 nF電容改變範圍內，可感測外力的範圍由2 N增加至3.5 N。

Conventional force sensors are commonly made of rigid material, which are prone to fatigue and cracking. In this study, the micro force sensors were fabricated by using polydimethylsiloxane (PDMS) material with capability of measuring both normal and shear forces. It’s more suitable for fabrication of force sensors than rigid material due to its flexibility. During the measurements, force is applied on the top of inlet reservoir of microchannel and the reservoir deforms and pushes the fluid into the channel. The applied force can be detected and quantified based on the movement of the liquid from inlet reservoir. In this study, both straight and cross microchannel devices were fabricated to detect the magnitude and direction of the applied forces.
In this study, two different experimental methods including optical method and non-optical method were conducted. For the optical method experiments, PFPE oil and DI water were served as working fluid in the inlet reservoir and base fluid in the microchannel respectively. For the cross microchannel devices, the displacement response in each channel would not be much different from the direction of the channel. For the non-optical method experiments, eGaIn and air were served as working fluid in the inlet reservoir and base fluid in the microchannel respectively. The influence of the initial capacitance and the comparison of four electrode types were examined. The capacitance response was similar after the normalization with the initial capacitance. In terms of sensitivity, the microchannel with the parallel electrode exhibited 44.39% higher than the one with cross-fingered electrode. In the normal force experiments, the capacitance variation of four channels increased to 1.5 nF with 2 N force applied. In the shear force experiments, there were three different increments of capacitance variation for four channels. The capacitance variation in the microchannel with parallel to the force direction with 0 degree showed 54% more capacitance increase than the microchannels at 90 degree direction. It showed up to 95.8% higher than the capacitance in microchannel with 180 degree to the force direction. When the force applied 45 degree toward to the center of cross microchannel, there are two different rates of capacitance variation observed. The capacitance in microchannels with 45 degree to the force direction show 33.69% more than the ones in the microchannels at the opposite direction. Therefore, shear force measurements can be demonstrated by the micro force sensors with cross microchannel design.
In practical application, the straight microchannel device with eGaIn and air was positioned at the robotic gripper and a calibration curve was applied to get the magnitude of the gripping forces during the robotic gripper operation. Additionally, the ferrofluid was used as base fluid and the response of capacitance would change with the magnetic field applied. The range of force measurement can be extended from 2 N to 3.5 N and it could be used to adjust the application range of the force sensors in this study.

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