非均勻表面和液滴特性在固液摩擦奈米發電機下之研究

Abstract

摩擦起電是一種常見的環境現象，當許多材料在不經意的接觸或摩擦時，會發生電荷分離，從而產生靜電。在過去，人們通常會將這種現象視為負面影響。在2013年Zong Hong ,Lin 等人提出固液摩擦奈米發電機(solid-liquid triboelectric nanogenerator，SLTENG)，開啟了摩擦起電一大發展領域。這個裝置是通過材料之間的摩擦，在固體與液體接觸界面處產生電荷分離和聚集，最後產生電流與電壓。在先前的文獻中，發現增加表面結構會改變表面潤濕性和水滴滑動速度，最後進而影響到輸出電壓。但較少研究探討表面結構、表面潤濕性以水滴滑動速度分別會對輸出電壓影響，在本研究中，設計一個新的裝置能夠獨立探討這些因素對輸出電壓所造成的影響。 本研究採用旋轉塗佈的方法製備摩擦介電層，並以ITO玻璃作為電極、PTFE作為摩擦介電層。為實現摩擦層的連續性親疏水變化，我們在PTFE中添加二氧化矽顆粒，形成複合介電層，使表面呈現連續性的親疏水變化。我們研究了表面潤濕性、水滴滑動速度與輸出電壓之間的相互關係。發現當水滴自由滑動時，輸出電壓很容易受到滑動速度的影響，而在等速度滑動時，當表面變得親水，使得接觸角減小，最終導致輸出電壓下降。接著，我們加入不同顆粒大小的微米玻璃珠，使表面產生均勻和非均勻的微米結構。我們觀察到在均勻情況下，由於表面結構增加導致表面接觸角上升，最終使輸出電壓提高。而在非均勻情況下，表面結構增加並未改變表面接觸角，卻因表面摩擦面積的增加而使輸出電壓上升。之 後我們有添加混合顆粒於表面，並且發現表面會因為結構增加，使得接觸角變大、摩擦面積增加，最終導致輸出電壓上升。最後，我們改變了液滴的性質，通過在液滴中添加介面活性劑，發現隨著添加濃度的增加，由於液滴表面接觸角下降，導致水滴滑動速度變緩慢，產生拖曳現象，進而降低輸出電壓。

Frictional electrification is a common environmental phenomenon where contact or friction between various materials leads to charge separation, resulting in static electricity. In the past, this phenomenon was often considered a negative effect. However, in 2013, Zong Hong Lin and others proposed the solid-liquid triboelectric nanogenerator (SLTENG), opening up a significant development area in the field of frictional electrification. This device operates by generating charge separation and accumulation at the solid-liquid contact interface through friction between materials, ultimately producing electric current and voltage. Previous research has shown that increasing surface structures can alter surface wetting properties and water droplet sliding speed, consequently affecting the output voltage. However, there has been limited exploration of how surface structures, surface wetting properties, and water droplet sliding speed individually influence output voltage. In this study, a new device was designed to independently investigate the impact of these factors on output voltage. The study employed a spin-coating method to prepare the frictional dielectric layer, using ITO glass as the electrode and PTFE as the frictional dielectric layer. To achieve continuous hydrophobic-hydrophilic variations in the frictional layer, silica particles were added to PTFE to form a composite dielectric layer, creating a surface with continuous hydrophobic-hydrophilic changes. The research investigated the interrelationships between surface wetting properties, water droplet sliding speed, and output voltage. The findings revealed that during free droplet sliding, output voltage was significantly influenced by sliding speed. Under constant sliding speed conditions, when the surface became more hydrophilic, resulting in a decrease in contact angle, it ultimately led to a decrease in output voltage. Subsequently, micron-sized glass beads of different sizes were introduced to create uniform and non-uniform microstructures on the surface. In uniform cases, the increase in surface structure resulted in an increase in contact angle, ultimately raising the output voltage. In non-uniform cases, although surface structure increased without changing the contact angle, the increase in frictional surface area led to an increase in output voltage. Furthermore, the addition of mixed particles on the surface was observed to increase surface structure, leading to a larger contact angle and increased frictional surface area, ultimately resulting in an increase in output voltage. Finally, the study altered the properties of the droplets by adding surfactants, finding that with an increase in concentration, the contact angle decreased, causing a slowdown in water droplet sliding speed, generating a dragging effect, and consequently reducing output voltage.