It is well known that charged colloidal particles move up (or more rarely down) gradients in salt concentrations. Patrick Warren showed theoretically that by crossing gradients of two different salts in solution, small electric currents can be generated, effectively instantaneously across the whole solution. In other words if you set up two salt sources then the currents span the whole solution, without needing for the salts to diffuse across the system. In this sense, there is action at a distance. A postdoc, Ian Williams, working with Joe Keddie and me, showed this in experiment for the first time, this was not easy but the results are cute.
Older work on transport in living cells
The complex viscous energy-consuming fluid inside cells is very far from uniform, and very far from thermodynamic equilibrium. In a Physical Review Letter (arXiv), I suggest that larger particles (about 100 nm across) inside cells may move around in cells at least partly by surfing these gradients. Motion of particles due to concentration gradient is called diffusiophoresis, which is quite topical at the moment.
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