Region-dependent volumetric oscillation of self-oscillating gels with gradient transducers.

Heartbeats with different ventricular contractions vary with heart regions, which can be described as anisotropy. Herein, we report self-oscillating gels which exhibit region-dependent anisotropic volumetric oscillation behavior similar to that of the heart. We installed a (Ru(bpy) 3 ) gradient transducer on self-oscillating gels by employing slow and unidirectional diffusion in the gels and dipping part of the gel into a Ru(bpy) 3 -NHS solution. We found that the spatial distribution of Ru(bpy) 3 in the gel caused region-dependent swelling/deswelling behavior depending on the redox state. We also confirmed that gel regions with smaller Ru(bpy) 3 amounts exhibit lower amplitudes than those with larger amounts of Ru(bpy) 3 during the Belousov-Zhabotinsky (BZ) reaction. These results are important in the design of self-oscillating soft actuators or machines, such as a biomimetic pump with desirable anisotropic oscillating behavior.