Fabrication of submillimeter-sized spherical self-oscillating gels and control of their isotropic volumetric oscillatory behaviors

In this study, we established a fabrication method and analyzed the volumetric self-oscillatory behaviors of submillimeter-sized spherical self-oscillating gels. We validated that the manufactured submillimeter-sized spherical self-oscillating gels exhibited isotropic volumetric oscillations during the Belousov-Zhabotinsky (BZ) reaction. In addition, we experimentally elucidated that the volumetric self-oscillatory behaviors ( i.e. , period and amplitude) and the oscillatory profiles depended on the following parameters: (1) the molar composition of N -(3-aminopropyl)methacrylamide hydrochloride (NAPMAm) in the gels and (2) the concentration of Ru(bpy) 3 -NHS solution containing an active ester group on conjugation. These clarified relationships imply that controlling the amount of Ru(bpy) 3 in the gel network could influence the gel volumetric oscillation during the BZ reaction. These results of submillimeter-sized and spherical self-oscillating gels bridge knowledge gaps in the current field because the gels with corresponding sizes and shapes have not been systematically explored yet. Therefore, our study could be a cornerstone for diverse applications of (self-powered) gels in various scales and shapes, including soft actuators exhibiting life-like functions. Here we fabricated millimeter-sized spherical self-oscillating gels by inverse-suspension polymerization. We found a specific relationship between the self-oscillatory behavior (the period and amplitude) and the amount of Ru(bpy) 3 in the gel network.