以壓電振子產生玻璃表面聲波之液珠排除裝置開發

Abstract

本研究旨在開發可與一般玻璃耦合的表面聲波元件，達到激發玻璃表面聲波用以進行液滴的排除的研究目標。在結構設計上，採用壓電陶瓷基板上沈積銀指叉電極之表面聲波元件，將其耦合在較厚之多層玻璃上，以間接的方式激發在玻璃表面產生表面聲波。在驅動方法上，本研究採用了方波調變頻率，避免高功率下連續驅動過久所造成的元件損壞。本研究並以有限元素分析及實驗驗證表面聲波元件之驅動之頻率，及於玻璃表面產生表面聲波之可行性，並利用等位函數兩相流建立了液滴驅動模型，並進行不同變數實驗，探討表面處理條件、耦合層材料、液珠體積大小、驅動電壓大小、驅動頻率、調變頻率及玻璃基板傾角大小下對液滴驅動效率之影響，最後以噴霧實驗模擬了實際應用情境並驗證排水裝置的效能。本研究成功結合指叉狀之壓電振子，設計振動波長為3.3mm之電極配置，在輸入頻率為1.96MHz，方波調變頻率為100Hz，以及60V的驅動電壓下，結合矽橡膠之聲學耦合層以及經疏水之表面處理的玻璃，成功達到驅動在1秒內即可推動10微升的去離子水液珠，達到約180mm/s～220mm/s的平均速度。在噴霧實驗中，於兩秒內可以有效清除元件作用範圍內90%以上的液滴，並隨著玻璃擺放傾角由0度上升至10度，清除效率提高，最大液珠驅動範圍可達20公分。

This study aims to develop a surface acoustic wave (SAW) device that can couple with a thick laminated glass to generate surface acoustic waves on the glass surface for water droplet removal. In the structural design, a PZT substrate with silver interdigital electrodes (IDT) is used to construct the SAW device, and it is coupled with the laminated glass with a silicone coupler. To indirectly induce surface acoustic waves on the glass surface, a square wave is used to modulate the driving signal. It can effectively eliminate overheating and damage to the SAW device due to continuous driving at high power for an extended period. Finite element analysis and experimental studies are conducted to verify the feasibility of using a SAW device to induce surface acoustic waves on glass. Lastly, the droplet removal performance is perimentally verified. In addition, its practical application is also confirmed by demonstrating that water droplets can be removed under a continuous spray. The experimental findings show that using a 3.3mm wavelength SAW device, driven by a square-wave modulated 1.96MHz sinewave at 60V and coupled with the glass using a silicone acoustic coupling layer, droplets can be moved at an average speed of 180mm/s to 200mm/s within 1 second. In the continuous spray experiments, more than 90% of the liquid droplets can effectively be removed within 2 seconds from up to 12cm distance. Finally, for a glass tilt angle from 0 degrees to 10 degrees, the removal efficiency increased, and the maximum range can increase over 20cm long.