  Tuning the electronic properties of a matter is of fundamental interest in
scientific research as well as in applications. Recently, the Mott
insulator-metal transition has been reported in a pristine layered transition
metal dichalcogenides 1T-TaS$_2$, with the transition triggered by an optical
excitation, a gate controlled intercalation, or a voltage pulse. However, the
sudden insulator-metal transition hinders an exploration of how the transition
evolves. Here, we report the strain as a possible new tuning parameter to
induce Mott gap collapse in 1T-TaS$_2$. In a strain-rich area, we find a mosaic
state with distinct electronic density of states within different domains. In a
corrugated surface, we further observe and analyze a smooth evolution from a
Mott gap state to a metallic state. Our results shed new lights on the
understanding of the insulator-metal transition and promote a controllable
strain engineering on the design of switching devices in the future.
