  Spatial phase inhomogeneity at the nano- to microscale is widely observed in
strongly-correlated electron materials. The underlying mechanism and
possibility of artificially controlling the phase inhomogeneity are still open
questions of critical importance for both the phase transition physics and
device applications. Lattice strain has been shown to cause the coexistence of
metallic and insulating phases in the Mott insulator VO2. By continuously
tuning strain over a wide range in single-crystal VO2 micro- and nanobeams,
here we demonstrate the nucleation and manipulation of one-dimensionally
ordered metal-insulator domain arrays along the beams. Mott transition is
achieved in these beams at room temperature by active control of strain. The
ability to engineer phase inhomogeneity with strain lends insight into
correlated electron materials in general, and opens opportunities for designing
and controlling the phase inhomogeneity of correlated electron materials for
micro- and nanoscale device applications.
