  In this work, we construct time-dependent wormhole solutions in the context
of $f(R)$ theory of gravity. The background matter is considered to be
traceless. By considering specific shape function and power-law expansion exact
solutions for $f(R)$ are found. The null and the weak energy conditions (NEC
and WEC) are checked for wormhole solutions. It is shown that the matter
threading the wormhole spacetimes with either accelerated expansion or
decelerated expansion satisfies the NEC and WEC.
