Self-Oscillating Polymer Materials—Gels, Vesicles, Micelles, Coacervates, Linear Polymers and Polymer Brushes Exhibiting Life-Like Autonomous Behaviors

The author for the first time developed “self-oscillating” polymer gels that spontaneously repeat swelling–deswelling changes in a closed solution without any on–off switching by external stimuli, such as heart muscle. The gel has an energy-conversion system involving an oscillatory chemical reaction (the Belousov–Zhabotinsky (BZ) reaction), which allows periodic mechanical motion of the polymer chain. Since the first report in 1996[1], the author has systematically developed the self-oscillating polymer materials (gels, vesicles, micelles, coacervates, linear polymers, polymer brushes, etc.) from analysis of fundamental behavior to construction and demonstration of material systems for potential applications in biomimetic materials, such as autonomous soft actuators, automatic transport systems, and functional fluids exhibiting autonomous sol–gel oscillations similar to those of amoeba [2]. BZ gels with similar properties have sometimes been called “Yoshida gels” [3]. Further optimal design toward life-like materials were carried out. For example, the myocardium repeats expansion and contraction in a uniaxial direction. In order to give the self-oscillating gel such anisotropic deformation, by introducing a layered structure like muscle fibers, the direction of contraction was controlled [4].
Further, by cyclically applying external mechanical stimulation to the self-oscillating gels, it was possible to find resonance with a “memory” of the resonant oscillation period maintained post stimulation, demonstrating an entrainment effect [5]. These findings help bridge the functions of biological systems with nonequilibrium chemical physics and pave the pathway to study the complicated biological problems using simpler biomimicking chemophysical systems.
When a large hollow capsule-type self-oscillating gel is fabricated, the propagation of chemical waves on the surface causes a unique cell-like fluctuation and buckling of the gel [6]. By analyzing the fluctuation in detail, we will explore the meaning of the biomembrane fluctuation phenomenon with marginal undulations for many important life phenomena such as cell motility, transport of intercellular substances, and cell division. Details will be discussed in the presentation.
References
[1] R. Yoshida, T. Takahashi, T. Yamaguchi and H. Ichijo: J. Am. Chem. Soc., 118, 5134 (1996).
[2] R. Yoshida: Polym. J., 54, 827 (2022).
[3] I.L. Mallphanov and V.K. Vanag: Russ. Chem. Rev., 90, 1263 (2021).
[4] W.S. Lee, T. Enomoto, A.M. Akimoto and R. Yoshida: Chem. Mater., 36, 2007 (2024).
[5] T. Geher-Herczegh, Z. Wang, T. Masuda, N. Vasudevan, R. Yoshida and Y. Hayashi: PNAS, 121, e2320331121 (2024).
[6] W.S. Lee, T. Enomoto, A.M. Akimoto and R. Yoshida: Mater. Horiz, 10, 1332 (2023).