  We study the possibility of transferring fermions from a trivial system as
particle source to an empty system but at topological phase as a mold for
casting a stable topological insulator dynamically. We show that this can be
realized by a non-Hermitian unidirectional hopping, which connects a central
system at topological phase and a trivial flat-band system with a periodic
driving chemical potential, which scans over the valence band of the central
system. The near exceptional-point dynamics allows a unidirectional dynamical
process: the time evolution from an initial state with full-filled source
system to a stable topological insulating state approximately. The result is
demonstrated numerically by a source-assistant QWZ model and SSH chain in the
presence of random perturbation. Our finding reveals a classical analogy of
quench dynamics in quantum matter and provides a way for topological quantum
state engineering.
