Delayed Mechanical Response to Chemical Kinetics in Self-Oscillating Hydrogels Driven by the Belousov–Zhabotinsky Reaction

Abstract

We show experimentally that chemical and mechanical self-oscillations in Belousov–Zhabotinsky hydrogels are inherently asynchronous, that is, there is a detectable delay in swelling–deswelling response after a change in the chemical redox state. This phenomenon is observable in many previous experimental studies and potentially has far-reaching implications for the functionality and response time of the material in future applications; however, so far, it has not been quantified or reported systematically. Here, we provide a comprehensive qualitative and quantitative description of the chemical-to-mechanical delay, and we propose to explain it as a consequence of the slow nonequilibrium swelling–deswelling dynamics of the polymer material. Specifically, standard hydrogel pieces are large enough that transport processes, for example, counterion migration and water diffusion, cannot occur instantaneously throughout the entire gel piece, as opposed to previous theoretical considerations. As a result, the volume response of the polymer to a chemical change may be governed by a characteristic response time, which leads to the emergence of delay in mechanical oscillation. This is supported by our theoretical calculations.

UV-Visible radiation modulation abilities of photon up-converting nanocapsules integrated with an oscillatory reaction

“…The oxidative bromination of malonic acid catalyzed by cerium ions (Belousov-Zhabotinsky reaction) is a well-known example of oscillatory chemical reaction, which is drawing attention in the field of bio-mimetic materials and neuromorphic engineering. [18][19][20][21][35][36][37] The oscillation of cerium ions, between the two redox states during the BZ reaction, results in a periodic change (with a period of ca. 70 s) of the optical density in the 300-380 nm range due to the different absorption coefficients of Ce(IV) and Ce(III) in this spectral region (Fig.…”

“…The BZ reaction can proceed in the oscillatory regime for many hours in a closed reactor, after a proper choice of the reagent concentrations. These oscillatory conditions have been recently used to prepare bio-mimetic smart materials 18,19 and perform optical communication experiments. 20–23…”

“…The BZ reaction can proceed in the oscillatory regime for many hours in a closed reactor, after a proper choice of the reagent concentrations. These oscillatory conditions have been recently used to prepare biomimetic smart materials 18,19 and perform optical communication experiments. [20][21][22][23] When cerium ions are used as BZ catalysts, they oscillate between the Ce(III) and Ce(IV) states, giving rise to large optical density oscillations in the UV region.…”

Electrotaxis behavior of droplets composed of aqueous Belousov-Zhabotinsky solutions suspended in oil phase

“…The discovery of electrotaxis phenomena in BZ droplets has an interesting application in the role of self-oscillating hydrogels, employing the use of BZ solutions, where electrotaxis can be utilised to break symmetry within the isotropic gel, causing the generation of a LC 40 . This will act as a form of control for the origin of the BZ reaction within the gel.…”

Nanogel Crosslinking-Based Belousov–Zhabotinsky Self-Oscillating Polyacrylamide Gel with Improved Mechanical Properties and Fast Oscillatory Response

“…For the traditional BZ self-oscillating gel, slow responsiveness and week toughness in BZ reaction medium remain to be solved. First, the solution diffusion is limited due to the heterogeneity of the gel system, leading to lag of gel responsiveness and longer oscillatory period of the traditional BZ gel than that of the corresponding homogeneous system under the same condition. Second, the spatial structure of the traditional BZ self-oscillating gel is easy to degrade and destroy in acidic BZ reacting solution.…”