Movement down a concentration gradient occurs fairly rapidly over short distances like a micron or so, like the size of a bacterium.

顺浓度梯度扩散在一微米左右的短距离内,相当迅速,一微米相当于一个细菌的大小

耶鲁公开课 - 生物医学工程探索课程节选

Bacterial cells are small, one to two microns in diameter and this shows a picture of a common bacterium called E. Coli.

细菌细胞很小,直径只有一到两个微米,这张图片是一种常见细菌,大肠杆菌

耶鲁公开课 - 生物医学工程探索课程节选

And, in this case, they had foil that was less than a micrometer thick.

这样的话，他们采用的箔的厚度小于一微米。

麻省理工公开课 - 固态化学导论课程节选