Controlling the dynamic behavior of heterogeneous self-oscillating gels

Abstract

Polymer gels undergoing the Belousov–Zhabotinsky (BZ) reaction exhibit autonomous, coupled chemical and mechanical oscillations. The ruthenium catalyst that contributes to the rhythmic swelling and deswelling of the gel is chemically grafted to the backbones of the polymer chains. Using both experiments and computer simulations, we examine films of heterogeneous BZ gels where the catalyst is localized in distinct sub-millimeter sized patches, and these BZ patches are surrounded by a non-reactive polymer network. The photo-polymerization method for sample fabrication permits control over the size of the disk-shaped patches, the ruthenium concentration in each of the disks, and arrangement of the disks in the non-reactive matrix. We first consider two distinct disks of the BZ gel that differ in size or the concentration of catalyst, [Ru]. By varying the separation between the disks, we isolated conditions necessary for the synchronization between the chemo-mechanical oscillations within these BZ patches. We then considered an arrangement of four disks and demonstrated that the two-dimensional propagation of the traveling wave within the film could be controlled by tailoring the size and [Ru] in the patches. Subsequently, we present results on the computational modeling of such heterogeneous self-oscillating gels. We demonstrate that the simulations capture the experimentally observed effects of the catalyst concentration, patch size, and inter-patch distance on the synchronization of oscillations in the neighboring BZ gels. Taken together, the experimental and computational studies reveal how the synchronization effects can be utilized to control the dynamical behavior of the entire system.