  Using a simple setup to bend a flexible substrate, we demonstrate
deterministic and reproducible in-situ strain tuning of graphene electronic
devices. Central to this method is the full hBN encapsulation of graphene,
which preserves the exceptional quality of pristine graphene for transport
experiments. In addition, the on-substrate approach allows one to exploit
strain effects in the full range of possible sample geometries and at the same
time guarantees that changes in the gate capacitance remain negligible during
the deformation process. We use Raman spectroscopy to spatially map the strain
magnitude in devices with two different geometries and demonstrate the
possibility to engineer a strain gradient, which is relevant for accessing the
valley degree of freedom with pseudo-magnetic fields. Comparing the transport
characteristics of a suspended device with those of an on-substrate device, we
demonstrate that our new approach does not suffer from the ambiguities
encountered in suspended devices.
