  The interaction and tunneling conductance between oppositely located ends of
coaxial carbon nanotubes are studied by the example of two (11,11) nanotubes
with open ends terminated by hydrogen atoms. The Green function formalism is
applied to determine the tunneling current through the nanotube ends as a
function of the distance between the ends, relative orientation of the
nanotubes and voltage applied. The energy favorable configuration of the
coaxial nanotubes is obtained by the analysis of their interaction energy at
different distances between the nanotube ends and angles of their relative
rotation. Using these calculations, a general scheme of the force sensor based
on the interaction between ends of coaxial nanotubes is proposed and the
relation between the tunneling conductance and measured force is established
for the considered nanotubes. The operational characteristics of this device as
a magnetic field sensor based on measurements of the magnetic force acting on
the coaxial nanotubes filled with magnetic endofullerenes are estimated.
