  We have investigated a brane world model in which the gravitational field in
the bulk is described both by a metric tensor and a minimally coupled scalar
field. This scalar field is taken to be a chameleon with an appropriate
potential function. The scalar field interacts with matter and there is an
energy transfer between the two components. We find a late-time asymptotic
solution which exhibits late-time accelerating expansion. We also show that the
Universe recently crosses the phantom barrier without recourse to any exotic
matter. We provide some thermodynamic arguments which constrain both the
direction of energy transfer and dynamics of the extra dimension.
