以彎曲結構提升孔洞駐極體感測能力之研究

Improvement of ElectroMechanical Film sensitivity by using a curved structure

郭凱鈞(Kai-Chun Kuo)

指導教授 ： 李世光

共同指導教授 ： 許聿翔(Yu-Hsiang Hsu)

國立臺灣大學/工學院/應用力學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202103647

摘要

本論文主旨為以商用孔洞駐極體材料(ElectroMechanical Film)製作感測器，透過曲面結構提升其靈敏度，並與平面感測器作比較，然而，在曲面結構上的應力同時存在拉應力與壓應力，這將會降低曲面感測器的靈敏度，因此設計三種不同的感測器貼法，分別是貼於曲面結構上方(CTS)、曲面結構下方(BS)與曲面結構壓力源的側邊(STS)，來比較不同感測器位置的靈敏度差異。
曲面感測器主要由兩個部分所組合而成，分別是EMFi孔洞駐極體感測器與底部的不銹鋼薄片，感測器利用PEDOT:PSS當作電極，做成雙層結構以減少外部雜訊，並提升訊號強度，底部的不銹鋼薄片，可以提供感測器彎曲變形，使外力所產生的應力與應變可以有效分布於感測器上，當感測器貼於CTS時，模擬結果顯示曲面結構感測器其靈敏度皆大於平面結構，當感測器曲率半徑為12 mm時，其靈敏度為平面實心結構(FL)的4.23倍，為平面中空結構(FS)的2.67倍，實驗上利用壓力計與振盪器來量測感測器的靈敏度，並透過雷射位移計量測感測器的正向應變(NS)，不論何種壓力源，曲面感測器靈敏度至少為FL的1.7倍以上，而FS則是在0.05 N以下有相當高靈敏度。
實驗上，當壓力源為1 mm薄板(T1)，感測器曲率半徑為36 mm，NS為0.05，比較BS、STS、CTS與FL的靈敏度，不論是BS、STS或CTS，曲面感測器的靈敏度至少為FL的3.97倍以上，STS相對CTS來說，靈敏度提升2%，BS相對CTS提升76%，以目前實驗結果來說，貼於BS能有效提升感測器的靈敏度。
綜合以上，利用曲面結構能提升EMFi感測器的靈敏度，但若可以只保留感測器受曲面結構形變所產生的訊號，也就是將感測器貼於BS或STS，則能進一步提升曲面感測器的靈敏度。

關鍵字

孔洞駐極體 ； 曲面感測器 ； EMFi

並列摘要

The goal of this study is to use a curved structure to increase the sensitivity of a commercial ElectroMechanical Film. The curve structure introduces a bending deformation and can be used to increase sensitivity. However, the stress on the curved structure contains both tensile stress and compressive stress, which will reduce the sensitivity of the curved sensor. Therefore, three different sensor attachment methods are designed, which are attached to the center top surface (CTS) of the curved structure、the bottom surface (BS) of the curved structure and the side top surface (STS) of the curved structure. Those methods are used to compare the sensitivity differences.
The curved sensor is constructed with a folded EMFi sensor and a stainless-steel sheet. Flexible PEDOT:PSS polymer is used as the sensor electrodes. The folded design of the EMFi sensor can increase signal output and reduce electromagnetic interference. The curved stainless-steel sheet can deform along with the external force and create lateral deformation on the EMFi film. When the sensor is attached to the CTS , the finite element analysis shows that the sensitivity can increase by 4.23 times that of a flat solid structure (FL) and 2.67 times that of a flat suspension structure (FS) with a curved sensor with 12 mm curvature. Experimental study shows that regardless of the pressure source, the sensitivity of the curved sensor is at least 1.7 times that of the FL solid sensor. The FS has a very high sensitivity when the applied force is below 0.05 N.
In experiment, when the pressure source is a 1 mm thin plate (T1), the sensor has a radius of curvature of 36 mm, and NS is 0.05. Compare the sensitivity of BS, STS, CTS and a FL solid structure, whether it is BS, STS or CTS, the sensitivity of the curved sensor is at least 3.97 times that of the FL. Compared with the CTS, the sensitivity of STS is increased by 2%, and the sensitivity of BS is increased by 76% compared with CTS. Based on the current experimental results, attaching to the BS can effectively improve the sensitivity of the sensor.
In summary, we verify that using a curve structure can effectively increase the sensitivity of a commercial ElectroMechanical Film, but if the curved sensor can only retain the signal generated by the deformation of the curved structure, the sensitivity of the curved sensor can be further improved.

並列關鍵字

porous electret ； curved sensor ； EMFi

參考文獻

R. Moreno and B. J. J. o. a. p. Gross, "Measurement of potential buildup and decay, surface charge density, and charging currents of corona‐charged polymer foil electrets," vol. 47, no. 8, pp. 3397-3402, 1976.

J. A. Giacometti, P. Ribeiro, M. Raposo, J. Marat‐Mendes, J. Carvalho Campos, and A. S. J. J. o. a. p. DeReggi, "Study of poling behavior of biaxially stretched poly (vinylidene fluoride) films using the constant‐current corona triode," vol. 78, no. 9, pp. 5597-5603, 1995.

M. Paajanen, J. Lekkala, K. J. S. Kirjavainen, and A. A. Physical, "ElectroMechanical Film (EMFi)—a new multipurpose electret material," vol. 84, no. 1-2, pp. 95-102, 2000.

J. Lekkala and M. Paajanen, "EMFi-New electret material for sensors and actuators," in 10th International Symposium on Electrets (ISE 10). Proceedings (Cat. No. 99 CH36256), 1999, pp. 743-746: IEEE.

S. Rajala and J. J. P. E. Lekkala, "PVDF and EMFi sensor materials—A comparative study," vol. 5, pp. 862-865, 2010.