Dimensional and Structural Control of Silica Aerogel Membranes for Miniaturized Motionless Gas Pumps

详细信息    查看全文

• 作者：Shanyu Zhao ; Bo Jiang ; Thomas Maeder ; Paul Muralt ; Nayoung Kim ; Santhosh Kumar Matam ; Eunho Jeong ; Yen-Lin Han ; Matthias M. Koebel
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：August 26, 2015
• 年：2015
• 卷：7
• 期：33
• 页码：18803-18814
• 全文大小：636K
• ISSN：1944-8252

文摘

With growing public interest in portable electronics such as micro fuel cells, micro gas total analysis systems, and portable medical devices, the need for miniaturized air pumps with minimal electrical power consumption is on the rise. Thus, the development and downsizing of next-generation thermal transpiration gas pumps has been investigated intensively during the last decades. Such a system relies on a mesoporous membrane that generates a thermomolecular pressure gradient under the action of an applied temperature bias. However, the development of highly miniaturized active membrane materials with tailored porosity and optimized pumping performance remains a major challenge. Here we report a systematic study on the manufacturing of aerogel membranes using an optimized, minimal-shrinkage sol鈥揼el process, leading to low thermal conductivity and high air conductance. This combination of properties results in superior performance for miniaturized thermomolecular air pump applications. The engineering of such aerogel membranes, which implies pore structure control and chemical surface modification, requires both chemical processing know-how and a detailed understanding of the influence of the material properties on the spatial flow rate density. Optimal pumping performance was found for devices with integrated membranes with a density of 0.062 g cm^鈥? and an average pore size of 142.0 nm. Benchmarking of such low-density hydrophobic active aerogel membranes gave an air flow rate density of 3.85 sccm路cm^鈥? at an operating temperature of 400 掳C. Such a silica aerogel membrane based system has shown more than 50% higher pumping performance when compared to conventional transpiration pump membrane materials as well as the ability to withstand higher operating temperatures (up to 440 掳C). This study highlights new perspectives for the development of miniaturized thermal transpiration air pumps while offering insights into the fundamentals of molecular pumping in three-dimensional open-mesoporous materials.