A team of scientists from Germany and Switzerland have used a scanning electron microscope to make a detailed examination of the foot of a jumping spider, Evarcha arcuata. They found that at the bottom of the spider’s leg is a tuft of hairs with each hair covered in more hairs. It is these smaller hairs that make the spider stick with a force that would allow them to grip to a ceiling while holding over 170 times their own body weight.
The small hairs are called setules and they use van der Waals forces acting between individual molecules located within one nanometre of each other. The research could lead to Post-it® notes that still stick even if wet and greasy or spacesuits for astronauts that help them stick to the walls of a spacecraft – just like a spider on the ceiling.
The van der Waals force exists because the movement of electrons in atoms and molecules causes them to become dipolar. A dipolar atom or molecule has a "positive-pole" and a "negative-pole". The positive-pole of one atom or molecule will be attracted to the negative-pole of another. This particular electrostatic attraction is called the van der Waals force, and is in some ways similar to the magnetic attraction between north and south poles of magnets.