Charge-Encoded Hydrogels Program Sign-Reversible Belousov−Zhabotinsky Wave Transport

Abstract

Reaction−diffusion waves provide a mode of spatiotemporal signal propagation in excitable media, yet passive control of their transport is typically limited to slowing or blocking. Here, using the Belousov−Zhabotinsky (BZ) reaction as a model-excitable system, we show that fixed ionic charge in polyelectrolyte hydrogels provides a sign-reversible, composition-tunable handle for wave transport. Anionic gels retard BZ waves by up to 35%, whereas cationic gels accelerate them by up to 23% above the incoming bulk reference; chemically distinct monomers reproduce the same sign-dependent trend. Reduced Oregonator modeling shows that diffusion-only control cannot account for the full response and is consistent with a shift in effective local excitability, without assigning a unique microscopic mechanism. A triangular anionic gel further converts local retardation into refraction-like steering. These results establish fixed-charge chemistry as a passive materials parameter for tuning BZ-wave speed and trajectory, providing a foundation for chemically encoded signal-routing materials.