Why do smaller fibers clean better?

Microfibers are able to attach themselves to even the smallest, most microscopic dirt particles—ones that normal cloth fibers (positively giant in comparison) crudely brush past. If forces were visible, you'd be able to see that there are adhesive forces (the forces of attraction) between microfibers and dirt. As you may have learned in school chemistry, these forces are called van der Waals forces after their discoverer, Nobel-prize winning Dutch chemist Johannes Diderik van der Waals (1837–1923). (Van der Waals forces explain why geckos can stick themselves to ceilings using zillions of tiny hairs on their toes.) Although there is only a microscopic amount of van der Waals force between one microfiber and any given dirt particle, remember that there are millions of microfibers in a cloth, so the overall sticking effect is magnified dramatically. That's why dirt, dust, and other stuff can be "hoovered up" by microfiber cloths. And it's also why you have to clean microfiber cloths so very thoroughly after you've used them. (Generally, it's best to boil a microfiber cloth in a saucepan and avoid washing it with normal detergents. Follow the manufacturer's instructions if you're unsure what to do.)