μm²/s
square micrometer per second
Diffusivityexact by definition
The square micrometre per second is 10⁻¹² m²/s. It is the unit cell biology reports diffusion in: a small protein diffuses through cytoplasm at roughly 10 to 30 μm²/s, a lipid in a membrane at about 1, and fluorescence recovery and single-particle tracking both report their fitted coefficients here.
Watch out: Diffusion time scales with the square of distance, so the unit is deceptive about speed. A coefficient of 10 μm²/s crosses a 10 μm cell in a few seconds but would take over a day to cross a centimetre, which is why large organisms need circulation rather than diffusion.
| 1 μm²/s | 0.000001 mm²/s |
Solvers that use diffusivity