Flashing Ratchet: molecular motors like kinesin exploit thermal fluctuations with an asymmetric (ratchet-shaped) potential. When the potential is ON, particles are trapped near minima. When it flashes OFF, they diffuse freely via Brownian motion. When it turns ON again, the asymmetry causes more particles to fall into the next well to the right than to the left — net directed motion emerges.
This does NOT violate the second law: the chemical energy driving the flashing (ATP hydrolysis) pays the thermodynamic cost. The ratchet mechanism explains how motor proteins step along cytoskeletal filaments, how ribosomes translocate RNA, and how F₁-ATPase rotates.