Mesoscale Chemical Systems, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands.
Lab Chip. 2013 Aug 7;13(15):3061-9. doi: 10.1039/c3lc41311j.
This paper presents a method for the fabrication of integrated porous silica layers in microfluidic channel networks by microfabrication techniques. Porous silica is obtained by anodization of silicon, followed by full conversion of the porous silicon network into porous silica by means of thermal oxidation. A series of experiments were performed with various channel layouts to determine the critical parameters, including the I-V characteristics and the optimal working potential for stable pore formation, during anodic etching. Typical test structures were anodized in 5% HF for 15 min at 1 V, yielding an average pore size of around 5.4 nm and porosity of 49%. Complete conversion of porous silicon into porous glass was accomplished with wet oxidation at 900 °C. The average pore size and porosity of porous glass network were around 3.8 nm and 34%, respectively. This decrease in both pore size and porosity is caused by the increase in molar volume when silicon oxidizes to silicon oxide. The transparency and the hydrophilicity of porous glass layers are evidenced by means of monitoring the diffusion of Rhodamine B fluorescent dye through the porous network. This fabrication method can be applied to (3-D) structured microfluidic channels and it is envisioned that the resulting porous silica layers can be employed for a wide range of application areas, such as membrane technology, catalyst supports, chromatography and electrokinetics.
本文提出了一种通过微加工技术在微流控通道网络中制造集成多孔硅层的方法。多孔硅是通过硅的阳极氧化获得的，然后通过热氧化将多孔硅网络完全转化为多孔硅。通过各种通道布局进行了一系列实验，以确定阳极刻蚀过程中的关键参数，包括 I-V 特性和稳定成孔的最佳工作电位。典型的测试结构在 1 V 下用 5%HF 阳极氧化 15 分钟，得到的平均孔径约为 5.4nm，孔隙率为 49%。多孔硅在 900°C 的湿氧化下完全转化为多孔玻璃。多孔玻璃网络的平均孔径和孔隙率分别约为 3.8nm 和 34%。这种孔径和孔隙率的减小是由于硅氧化为氧化硅时摩尔体积的增加引起的。通过监测罗丹明 B 荧光染料通过多孔网络的扩散，可以证明多孔玻璃层的透明度和亲水性。这种制造方法可以应用于（3-D）结构的微流控通道，并且可以设想，所得到的多孔硅层可以用于广泛的应用领域，例如膜技术、催化剂载体、色谱和电动学。
