可撓式垂直排列奈米碳管叢應變感測計

Abstract

奈米碳管應用於應變感測計已有許多項研究，但大多研究皆利用奈米碳管混和聚合物於薄膜，進而做成可撓式應變感測計，很少有單純垂直排列奈米碳管叢應變感測計之研究。本論文將先利用化學氣相沉積法，以控制成長區溫度的方式，在鋁箔紙上成長出不同高度的填鐵奈米碳管叢。本研究之填鐵奈米碳管具有均勻且等高及垂直排列特性。 本研究將利用垂直排列填鐵奈米碳管叢分別製作四種不同應變感測計，分別為第一類應變感測計、第二類應變感測計、第三類應變感測計及第四類應變感測計。其中最為特別的是第三類應變感測計，藉由施加外應力的方式把奈米碳管叢原始高度降低，並利用封裝等外在拘束的方式把縮短的奈米碳管叢拘束住，其方式可以增加奈米碳管叢之間的起始接觸面積，當有彎曲應變產生時，因為接觸面積改變率變大，進而提高應變規因子。 實驗結果顯示當奈米碳管高度接近於12.5μm時，有最高應變規因子表現；另一方面，利用12.5μm單層垂直排列填鐵奈米碳管叢製作成第三類應變感測計，可以得到208之應變規因子，線性度達到0.989；更近一步延伸為第四類應變感測計，應變規因子甚至可以達到367。除此之外，預先施加一外應力於第三類應變感測計是一個很重要的因素，可以發現其量值與應變規因子存在一簡單數學關係式，因此可藉由應變規因子，進而推出施加於應變感測計上之應力。最後經由簡單動態量測可發現經由多次上下振動測試後，電阻值依然對應變有著顯著變化，甚至利用本研究應變感測計成功量取人體脈搏波形圖。本研究之應變感測計具有高線性度、高再現性及高應變規因子表現。

There are many researches about producing strain sensors with carbon nanotubes (CNTs). But most of them are studying nanocomposite film of CNTs and polymer and using nanocomposite film to fabricate the strain sensor. There are few researches about fabricating the strain sensors with vertically aligned carbon nanotubes (VA-CNTs). In this research, we synthesize the different height of iron-filled CNTs on aluminum foil by controlling the synthesis temperature in furnace and using the chemical vapor deposition method (CVD). There are some characters for iron-filled CNTs in this research, such as uniformity, equal height and vertically aligned. In this research, we fabricate four different strain sensors by iron-filled VA-CNTs, such as sensor type 1, sensor type 2, sensor type 3 and sensor type 4. One of the most special is sensor type 3. We constrain the height of CNTs by using package method and exerting an external force to depress the initial height of CNTs. This method can enlarge the initial contact area between the CNTs. When the bending strain occurs in the CNTs, it will lead the change rate of contact area increase. That is why this result can enhance the gauge factor (GF). The experimental results show that the height of CNTs near 12.5μm has the best GF performance. We use 12.5μm single layer iron-filled VA-CNTs to fabricate the sensor type 3. We find out that this kind of sensor has the value 208 of GF and the value 0.989 of linearity. After that, we even extend this kind of CNTs to sensor type 4. The results show that the GF of sensor type 4 can reach to 367. Furthermore, previously exerting an external force to sensor type 3 is an important factor in our research. We find out that there is a mathematical relationship between the external force and the GF. So we can use the result of GF to derive the external force value which is exerted on the strain sensor. At the last, we also show that resistance still has the significant changes by the simple up-down-shaking dynamic measurement. We even successfully apply strain sensor to measure the human pulse. The strain sensors in this research have high linearity, good repeatability and big GF value.