Piezoelectric Response of Aligned Electrospun PVDF Nanofiber Membranes

• Main Authors: Wun-Yuan Zeng, 曾玟媛
• Other Authors: Chang-Mou Wu
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/6ewn7b

碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 106 === Polyvinylidene fluoride (PVDF) is a popular piezoelectric polymer because of its high flexibility, biocompatibility, and simplicity in production. These features make PVDF attractive in energy conversion, between mechanical force and electrical power, applications such as strain sensors, mechanical actuators and energy harvesters. The aforementioned applications rely on the piezoelectric property of PVDF and it is well-known that appropriate mechanical stretching and electrical polarization are essential factors to achieve good piezoelectricity. Electrospinning (ES) processes can provide PVDF fibers mechanical stretching and electrical poling simultaneously to produce ultrafine and well-distributed nanofibers. Furthermore, previous studies discovered that the addition of nanoparticles, such as carbon nanomaterials or metallic nanoparticles, can help improve the β content of the electrospun PVDF nanofibers. In this study, a rotation drum was used during the electrospinning process to collect aligned PVDF nanofibers. By adjusting the rotating speed and the applied voltage, the electrospun PVDF nanofiber membranes collected by the rotating drum showed a higher β content, better piezoelectric coefficient (d33) and enhanced mechanical property than the randomly oriented nanofiber membranes collected on a fixed copper grid. The optimal β content and the d33 value of the aligned PVDF fiber membranes reached 88% and 27.4 pC/N at a rotating speed of 3000 rpm with an applied electric field of 1200V/cm. Moreover, the aligned PVDF nanofibers added with carbon nanotubes (CNT) further increased the β phase content to 89% and d33 value to 31.3 pC/N. The piezoelectric response of the as-received PVDF nanofiber membranes were evaluated by three types of mechanical loading: compression, tensile and bending. In the compressive loading range between 200 N to 350 N, the output voltage of the piezoelectric units with aligned electrospun PVDF/CNT increased linearly with the applied loading and presented good stability during the cyclic loading, where its sensitivity was 2.26 mV/N while the piezoelectric units with aligned electrospun PVDF and with randomly oriented electrospun PVDF had sensitivities of 1.93 mV/N and 1.30 mV/N, respectively. In the applied tensile strain range between 4% to 10%, the piezoelectric units with aligned electrospun PVDF/CNT can output linearly with increasing tensile strain, showing sensitivity of 19.22 mV/N while the piezoelectric units with aligned electrospun PVDF and with randomly oriented electrospun PVDF had sensitivities of 18.52 mV/N and 15.32 mV/N, respectively. In the bending angle range between 10° to 180°, all three prepared piezoelectric units generated highest output voltage at bending angle of 100°. When being bent at 100°, the unit with aligned electrospun PVDF/CNT outputted 1.89 V while the piezoelectric units with aligned electrospun PVDF and with randomly oriented electrospun PVDF outputted 1.52 V and 0.75 V, respectively.