When Neils Bohr shook hand with Werner Heisenberg, what kind of force they exerted?

When the Neils Bohr shook hand with Werner Heisenberg, the atoms of the two hands come in contact with each other and charged particles of the atoms in their hands exert forces on each other and, as a result, a measurable electromagnetic force is produced.

There is no nuclear force or gravitational force acting in this case.