System and method for separating particles in suspension utilizing bubbles

Abstract

Disclosed is a process for separating suspended particles based on size. When confined in a tube, a bubble moves relative to the liquid as a small fraction of the liquid leaks backwards through a very thin gap between the bubble and the internal wall of the tube. The lubricating film formed around the bubble can be fine-tuned by simply changing the average flow speed. With this thin film of liquid, the confined air bubble can be used to separate particles in, for example, poly-disperse microspheres suspensions. As the bubble passes through the suspension, only particles smaller than the liquid gap thickness can leak through the gap towards the back of the bubble, resulting a filtered particle suspension containing only small particles at the back of the bubble. Compared to the traditional methods, this particle separation process is easy to perform, and is flexible in filtering different suspensions with one set-up. Due to the flexibility of the bubble interface and the special film thickness profile of a translating confined bubble, this process also avoids clogging, and can be easily adapted to, e.g., separate different poly-disperse suspensions based on size.