Fig. 2: Mass transport in short- and long-pitch devices.

Concentration distribution of TPPS3 at selected cross-sections along the entire length of the helical channel (four turns) for Rshort and Rlong devices (left and right, respectively). The first picture at θ = 0 corresponds to the inlet region and shows the concentric 3D focussing. Snapshots taken from Supplementary Movie 1. The concentration distribution of TPPS3 evolves in a markedly different way in the two devices, with the porphyrin remaining exposed exclusively to the CCW vortex in Rlong and to both the CCW and the CW vortices in Rshort.