Stud On Electrodrven Of Ionic Liquids And Variable Focus Ionic Liquid Lenses

In recent years, miniaturization becomes the trend of science and technology development. Beginning with the field of electronics, it extended to mechanical engineering, fluid mechanics and other fields. Reduction in the size is much easier for device integration, making the device has greatly improved in terms of accuracy, throughput, and function. In this context, microfluidic technology of controlling tiny droplets on the microchip was born. With the large modulation amplitude, low energy consumption, short response time, good repeatability, etc., electrowetting has become an important method for microfluidic. Water or aqueous solution of inorganic salts was mostly used as traditional electrowetting materials. Constrained by the physical and chemical properties of water, there are many drawbacks, such as volatility, poor thermal stability, and narrow operating temperature range. Thus, finding a new type of electrowetting conductive media that could fundamentally overcome these problems has become an urgent need for the development of electrowetting. As the new green materials, ionic liquids have a wide liquid temperature range, non-volatility, non-flammability, strong conductivity, high heat capacity, negligible vapor pressure, good stability, friendly environment and non toxicity. In this research work, the electrowetting of ionic liquids was investigated. The equivalent circuit model of electrowetting was established and the expression of the contact angle under the AC signal was derived. The electrowetting of ionic liquids experimental setup was built, and the contact angle of ionic liquids under different applied voltages was studied. The contact angle and field distribution in electrowetting phenomenon under different voltages were simulated using finite element software. Comparison between electrowetting of ionic liquids and that of traditional inorganic salts solution was made. The effects of DC voltage, frequency and amplitude of AC voltage, ambient temperature, cation and anion structure of ionic liquids and water content to the contact angle range, response time, and reversibility of electrowetting were all discussed respectively.The electrocapillary of ionic liquids was also investigated. The equivalent circuit model of the electrocapillary was established, and the theoretical height-of-rise expression of electrocapillary was derived under AC voltages. The electrocapillary of ionic liquids experimental setup was built, and the height-of-rise of ionic liquids under different applied voltages was investigated. The height-of-rise and field distribution in electrocapillary phenomenon under different voltages were simulated using finite element software. The effects of frequency and amplitude of AC voltage, cation and anion structure of ionic liquids and ambient temperature to the height-of-rise and response time of electrocapillary were all discussed respectively.Electrowetting-based variable focus liquid lenses have attracted considerable attention in mobile phones, barcode readers, medical equipment and various other optical systems. Nevertheless, the most frequently used conductive liquid in electrowetting-based variable focus liquid lenses has been limited to saline. The traditional saline-based variable focus liquid lenses may suffer from problems such as high focusing voltage, evaporating or freezing at relatively higher/lower temperatures, opacity in the near-infrared and even in most of the infrared range. Therefore, the electrowetting based ionic liquids variable focus lens was designed and fabricated in this paper. The focal length expression of the lens was derived theoretically. A test device was built; the image quality and focal length of the lens under different voltages were studied. The effects of frequency and amplitude of AC voltage, ambient temperature, cation and anion structure of ionic liquids, dimensions of the lens, thickness of insulating layer and volume of ionic liquids to the focal length, response time, and power consumption of the lens were all discussed respectively. In view of the good transmittance of ionic liquids in near-infrared, the properties of electrowetting based ionic liquids variable focus lens in near-infrared imaging was also tested. It shows a nice performance compared to traditional liquid lenses.The overall results of this dissertation illustrate that ionic liquids because of their excellent properties, are superior to aqueous electrolytes or other organic solvents as the media in electrodriven. The results showed attractive features involving non-volatility, wide operating temperatures and in particular high stability, fast response, and good reversibility at high temperatures. The performance of ionic liquid-based electrodriven could be further improved through optimal choice of ambient phase or rational design and synthesis of ionic liquids. The ionic liquid-based variable focus liquid lenses exhibits excellent performance over saline such as wide operating temperature, tunable focus behavior, low energy consumption and in particular high stability at high temperatures. The overall results of this dissertation provide the basis for the application and optimization of electrowetting based ionic liquids variable focus lenses.