Autonomous sequential deformation of microphase-separated Belousov-Zhabotinsky gel pillar arrays directed by Ag-contact-induced chemical waves.

Abstract

Belousov-Zhabotinsky (BZ) gels exhibit autonomous and periodic deformation driven by the BZ reaction, enabling sustained deformation dynamics without dependence on externally imposed on-off control. To utilize BZ gels as autonomous soft actuators, it is essential to design structures that convert the propagation of chemical waves generated by the BZ reaction into macroscopically observable mechanical deformations. To convert the spatiotemporal propagation of chemical waves into macroscopically observable sequential mechanical deformation, we fabricated a single continuous BZ gel structure containing millimeter-scale free-standing pillar arrays using a BZ-gel formulation previously shown to form a microphase-separated structure with an amplified swelling-deswelling response. Furthermore, by contacting the gel with a silver (Ag) wire, we introduced a local reaction-field perturbation that likely promoted preferential chemical-wave propagation while maintaining sustained redox oscillations in the BZ gel. A representative pillar exhibited a tip displacement of approximately 0.30 mm, and the chemical-wave peak propagated along the pillar array at approximately 1.7 mm min^-1. In the pillar array, direct tip tracking showed delayed x-displacement peaks along the wave-propagation direction and nearly synchronous motion of pillars positioned in parallel. Thus, chemical-wave propagation was read out as sequential deformation of multiple pillars within a single continuous gel. Moreover, the proposed approach provides design guidelines for converting spatiotemporal patterns generated by chemical reactions into directional actuation, contributing to the development of soft robotics and biomimetic devices based on self-oscillating gels.