Nonlinear dynamics of self-oscillating polymer gels

Abstract

Self-oscillating polymer gels driven by Belousov-Zhabotinsky (BZ) chemical reaction are a new class of functional gels that have a wide range of potential applications (e.g., autonomously functioning membranes, actuate artificial muscles). However, the precise control of these gels has been an issue due to limited investigations of the influences of key system parameters on the characteristics of BZ gels. To address this deficiency, we studied the self-oscillating behavior of BZ gels using the nonlinear dynamics theory and an Oregonator-like model, with focus placed upon the influences of various system parameters. The analysis of the oscillation phase indicated that the dynamic response of BZ gels represents the classical limit cycle oscillation. We then investigated the characteristics of the limit cycle oscillation and quantified the influences of key parameters (i.e., initial reactant concentration, oxidation and reduction rate of catalyst, and response coefficient) on the self-oscillating behavior of BZ gels. The results demonstrated that sustained limit cycle oscillation of BZ gels can be achieved only when these key parameters meet certain requirements, and that the pattern, period and amplitude of the oscillation are significantly influenced by these parameters. The results obtained in this study could enable the controlled self-oscillation of BZ gels system. This has several potential applications such as controlled drug delivery, miniature peristaltic pumps and microactuators.Polymer gels are mixtures of a large number of small solvent molecules dissolved into a polymer network [1]. Some polymer gels can swell or deswell, in a controlled manner, in response to external stimuli (e.g., pH [2], temperature [3], magnetism [4], electricity [5] and light [6]). Because of the distinctive characteristics of these gels (i.e., polymer gels with controlled response driven by external stimulations), they have been used for applications such as periodic precision devices (e.g., micropumps, smart control valves [7,8]) and environmental sensors (e.g., magneticfield sensor, pHresponsive device[9,10]).Besides external stimulation-controlled gels, self-oscillating polymer gels have also been developed which do not require external stimulations to rhythmically produce a dynamic response in volume (i.e., swelling and deswelling) [11,12], driven by Belousov-Zhabotinsky chemical reaction [13] (i.e., BZ gels). In BZ gels, catalyst ruthenium (i.e., Ru(bpy) 3 ) of the BZ reaction was chemically bundled on cross-linked polymer chains (Figure 1), and the BZ solution without the catalyst was dissolved into the polymer network. During the reduction-oxidation (redox) process of the BZ reaction in the gel-solution system, Ru(bpy) 3 continuously transforms between two valences, i.e., Ru(bpy) 2+ 3 and Ru(bpy) 2+ 3 . This reversible valence transformation is sustained by the coupling between gel swelling/deswelling and BZ reaction: BZ gels swell during the process of Ru(bpy) 2+ 3 Ru(bpy) 2+ 3 and deswell during the opposite process due to

Reaction-induced swelling of ionic gels

“…According to our previous study, 40,41 the kinetics of the chemical reaction in a reactive gel (eqn (1)) agree well with eqn (5) of the thermodynamics.…”

Self-regulated intelligent systems: where adaptive entities meet chemical oscillators

“…But it is not limited. Other techniques from interdisciplinary areas of computational simulation, 53,77,111,135,[142][143][144][145][146][147][148][149][150][151][152][153][154] supramolecular chemistry, 20,78 nanoscience, 86,87,95 biotechnology, 111 etc. may be utilized and a modularized, systematized and elaborated platform for the design of such systems is also expected.…”