Compress a colloidal fluid by moving a wall inward. At slow speeds, the work you inject approximates the equilibrium free energy change — the compression is reversible, and entropy production is minimal. At fast speeds, you might expect work and dissipation to grow without bound: push faster, waste more.
They don't. The injected work and entropy production are bounded, constrained by diffusive transport. Push the wall faster than the particles can rearrange, and the compression stalls — not mechanically (the wall moves), but thermodynamically. The particles nearest the wall compress, but the information about the compression cannot propagate through the fluid faster than diffusion allows. The far side of the container doesn't know the wall is moving. The maximum power you can inject scales linearly with the particle mobility — the transport coefficient sets a speed limit on thermodynamic work.
The structural insight is about the relationship between driving speed and response. In equilibrium thermodynamics, arbitrarily much work can be extracted by arbitrarily slow processes. Far from equilibrium, the mirror symmetry breaks: arbitrarily much work cannot be injected by arbitrarily fast processes. There is a ceiling set by the system's own dynamics. The fluid has a maximum rate at which it can absorb organized energy, and beyond that rate, the excess driving does not produce proportionally more entropy — it simply fails to couple to the system.
This is a specific version of a general principle: the system's own relaxation dynamics cap what can be done to it. You can drive faster than the response, but the excess driving passes through without thermodynamic effect. The piston moves, the particles near the wall compress, and the rest of the fluid waits.
(arXiv:2603.18618)