Microfluidic Validation of the Diffusional Bridging Effect Suppressing Dispersion in Multicapillary Flow Systems.

The efficiency of liquid chromatography separations could be strongly improved by changing the current packed bed columns by a bundle of parallel capillary tubes. In practice, however, the polydispersity effect, which emanates from the inevitable small differences in capillary diameter, completely ruins this potential. The concept of diffusional bridging, introducing a diffusive cross talk between adjacent capillaries, has recently been proposed to resolve this. The present contribution provides the first experimental proof for this concept and quantitatively validates its underlying theory. This has been accomplished by measuring the dispersion of a fluorescent tracer in 8 different microfluidic channels with different degrees of polydispersity and diffusional bridging. The observed degree of dispersion reduction agrees very well with the theoretical predictions, hence opening the road to the use of this theory to design a new family of chromatographic beds, potentially offering unprecedented performance.