- 學位論文
提升孔洞駐極體材料致動與感測特性之研究
Research and Development on Enhancing Porous Electret Sensing and Actuating Characteristics
摘要
本論文以孔洞駐極體材料的性質與製程改善為研究主軸。對於應用於超薄型可撓駐極體揚聲器的研究，本文將對以移動式多針電暈放電系統對駐極體產生空間電荷注入的各項參數進行探討，希望能夠提升大面積超薄型駐極體揚聲器的製作效率，以利其大型化的應用趨勢。此外本文將使用聚對二甲苯的氣相沉積方式在多孔聚四氟乙烯高分子材料基材上沉積特定圖案，藉以針對多孔聚四氟乙烯在超薄型可撓式駐極體揚聲器使用上，如中等水平的儲電能力與容易塑性變形等缺點加以修飾，經實驗證實，本論文所提出的改進方法可有效提升駐極體揚聲器的聲壓值2dB，並保有其低頻頻寬，因此使改進後的孔洞駐極體材料可被應用為一寬頻揚聲器。另外對於可撓式類皮膚感測器與超音波換能器等的研發，本論文提出一種多孔聚四氟乙烯薄膜與氟化三氟聚乙烯複合材料的製法，相對於常見的化學溶液製程，可有效且簡單的進行孔洞氟化三氟聚乙烯薄膜的製作，透過其孔洞結構可使整體薄膜具相當的柔軟性與空氣有較好的聲阻匹配等，使改進後的孔洞駐極體材料可有效的作為空氣介質中的超音波換能器，此外也將孔洞結構所營造出的不對稱之電偶極與偶極駐極體材料內部所具有的電偶極結合，使其可產生更佳的壓電效應，所產生的壓電係數為結合前的四倍，可因此增加其作為感測器壓力方向的靈敏度。這個特性可以降低感測器的橫軸雜訊，整體提昇感測器的應用潛能。
並列摘要
Improving the material property and manufacture process of porous electret were the main research targets in this thesis. With the application of ultra-thin flexible electret-speaker in mind, we identified the optimal parameters of using multiple-needle corona discharge system to enhance the production efficiency of large-area thin electret-speakers. The Parylene C was deposited in a particular pattern on the ePTFE substrate to modify the shortcomings of ePTFE such as medium charge storage stability and easy plastic deformation at low stress when adopted as ultra-thin flexible electret-speaker. The experimental results confirmed that the hybrid electret diaphragm can effectively increase the sound pressure level of electret loudspeaker 2dB and maintain the low-frequency response to form a wide bandwidth loudspeaker. In addition, we presented a novel method to form the porous structure of P(VDF-TrFE) by coating the solution of P(VDF-TrFE) onto the ePTFE substrate for developing flexible skin-like sensors and ultrasonic transducers. Comparing to the traditional chemical solution process, this newly developed method can easily produce porous structure of P(VDF-TrFE) to form large-area film. The ePTFE/P(VDF-TrFE) composite film is a suitable material for ultrasound transducer and film type sensor as its porous structure make the acoustic impedance of the film matched well with that of the air. It should be noted that porous ePTFE/P(VDF-TrFE) composite film is also softer, which makes it even more suitable for flexible ultrasonic or skin transducers. Finally, we combined the spatial dipole of porous electret and the dipole charge of dipole electret to enhance the piezoelectric effect and quadruple piezoelectric constant with an attempt to improve the sensor pressure directional sensitivity. This behavior can reduce the cross-axis sensitivity and thus enhance the potential of sensor applications.