Figure 2. Illustration of the assembly process.

The nanofibrils in the focused flow are illustrated as rods (the fibril length in relation to the channel width is exaggerated by approximately a factor of 300). The diffusion of Na ⁺ , from addition of NaCl in the focusing liquid, is illustrated with a blue tint. The rows of small images above and below the central image illustrates the hydrodynamical, molecular and electrochemical processes involved. (a) Brownian diffusion (illustrated with the dashed arrows) affects the orientation of a single fibril, (b) hydrodynamically induced alignment (illustrated by solid, grey, arrows) occurs during the acceleration/stretching, (c) Brownian diffusion continues to act after the stretching has ceased, (d) Brownian diffusion is prevented by the transition to a gel. The lower row of small images illustrate how the electrostatic repulsion (illustrated by the red area representing the Debye length) decreases from e to h as the Debye length is decreased with increasing Na⁺ concentration or by protonation of the carboxyl groups on the fibril surface.