  We study the stochastic resonance (SR) of a flexible polymer surmounting a
bistable-potential barrier. Due to the flexibility that can enhance crossing
rate and change chain conformations at the barrier, the SR behaviors manifest
many features of an entropic SR of a new kind, such as the power amplification
peaks at optimal chain lengths and elastic constants as well as the optimal
noise strengths. The pronounced peaks that emerge depending on the chain
lengths and conformation states suggest novel means of manipulating
biopolymers, such as efficient separation methods, within undulating channels.
