  Gas molecules trapped between graphene and various substrates in the form of
bubbles are observed experimentally. The study of these bubbles is useful in
determining the elastic and mechanical properties of graphene, adhesion energy
between graphene and substrate, and manipulating the electronic properties via
strain engineering. In our numerical simulations, we use a simple description
of elastic potential and adhesion energy to show that for small gas bubbles
($\sim 10$ nm) the van der Waals pressure is in the order of 1 GPa. These
bubbles show universal shape behavior irrespective of their size, as observed
in recent experiments. With our results the shape and volume of the trapped gas
can be determined via the vibrational density of states (VDOS) using
experimental techniques such as inelastic tunneling and inelastic neutron
scattering. The elastic energy distribution in the graphene layer which traps
the nanobubble is homogeneous apart from its edge, but the strain depends on
the bubble size thus variation in bubble size allows control of the electronic
and optical properties.
