Microfluidic sorting with high-speed single-layer membrane valves
Original entry: Caspar Floryan, APPHY 225, Fall 2010
Biocompatible surfactants for water-in-fluorocarbon emulsions C. Holtze, A. C. Rowat, J. J. Agresti, J. B. Hutchison, F. E. Angilè, C. H. J. Schmitz, S. Koester, H. Duan, K. J. Humphry, R. A. Scanga, J. S. Johnson, D. Pisignano and D. A. Weitz, Lab Chip 8,1632-1639 (2008).
This paper presents a new microfluidic sorting device. Sorting is the ability to extract specific droplets from a larger population. This device does a binary sort, isolating fluorescing droplets into a collector channel and refusing the remainder into a waste channel by means of an active valve. This method has several advantages over previous droplet sorting techniques.
Existing sorting techniques take advantage of several innate droplet properties. droplets have been separated by density, size, dielectric properties, and various fluorescence methods. Their shortcomings include passiveness, lack of dielectric contrast with the surrounding medium, and their applicability to only a small subset of droplet populations.
The device introduced in this paper sorts with a high-speed single-layer membrane valve in combination with an asymmetric channel junction. The asymmetry causes droplets to flow into the waste stream unless acted on by the valve. When the valve is actuated the asymmetry is inverted and flow flow into a collection channel. The valve is fast, actuating at hundreds of hertz, and versatile, with applicability to droplets, cells and particles.