Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, United States.
Langmuir. 2012 Jan 10;28(1):37-41. doi: 10.1021/la203824f. Epub 2011 Dec 6.
We present a microfluidic approach for the controlled encapsulation of individual gas bubbles in micrometer-diameter aqueous droplets with high gas volume fractions and demonstrate this approach to making a liquid shell, which serves as a template for the synthesis of hollow inorganic particles. In particular, we find that an increase in the viscosity of the aqueous phase facilitates the encapsulation of individual gas bubbles in an aqueous droplet and allows control of the thickness of a thin aqueous shell. Furthermore, because such droplets contain a finite amount of water, uncontrolled hydrolysis reactions between reactive inorganic precursors and bulk water can be avoided. We demonstrate this approach by introducing reactive inorganic precursors, such as silane and titanium butoxide, for sol-gel reactions downstream from the formation of the bubble in a droplet and consequently fabricate hollow particles of silica or titania in one continuous flow process. These approaches provide a route to controlling double-emulsion-type gas-liquid microstructures and offer a new fabrication method for thin-shell-covered microbubbles and hollow microparticles.
我们提出了一种微流控方法，用于将单个气泡在具有高气体体积分数的微径水滴中进行受控封装，并展示了这种方法来制造液体壳，该液体壳可用作合成中空无机颗粒的模板。特别地，我们发现增加水相的粘度有助于将单个气泡封装在水滴中，并可以控制薄水壳的厚度。此外，由于这种液滴包含有限量的水，因此可以避免反应性无机前体与体相水之间的不可控水解反应。我们通过在形成气泡之后的液滴中引入反应性无机前体（例如硅烷和钛酸丁酯）来证明这种方法，从而在一个连续流动过程中制备出二氧化硅或二氧化钛的空心颗粒。这些方法提供了控制双乳液型气-液微结构的途径，并为具有薄壳覆盖的微泡和中空微颗粒提供了新的制造方法。
