  we have fabricated transparent electronic devices based on graphene materials
with thickness down to one single atomic layer by the transfer printing method.
The resulting printed graphene devices retain high field effect mobility and
have low contact resistance. The results show that the transfer printing method
is capable of high-quality transfer of graphene materials from silicon dioxide
substrates, and the method thus will have wide applications in manipulating and
delivering graphene materials to desired substrate and device geometries. Since
the method is purely additive, it exposes graphene (or other functional
materials) to no chemical preparation or lithographic steps, providing greater
experimental control over device environment for reproducibility and for
studies of fundamental transport mechanisms. Finally, the transport properties
of the graphene devices on the PET substrate demonstrate the non-universality
of minimum conductivity and the incompleteness of the current transport theory.
