Harmonic resonance and entrainment in self-oscillating polymer gels

Smart polymer materials that are nonliving yet exhibit complex “life-like” or biomimetic behaviors have been the focus of intensive research, in the quest to broaden our understanding of how living systems function under nonequilibrium conditions. Identification of how chemical and mechanical coupling can generate resonance and entrainment with other cells or external environment is an important research question. Prof. R. Yoshida developed “self-oscillating” polymer gels which convert chemical energy of Belousov–Zhabotinsky (BZ) reaction to mechanical oscillation. This time, through collaboration with University of Reading, UK, by cyclically applying external mechanical stimulation to the BZ gels, it was possible to find resonance, either with the stimulation’s fundamental frequency or an n× or (1/n)× harmonic of it, and then the system kept a “memory” of the resonant oscillation period and maintained it post stimulation, demonstrating an entrainment effect. 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. This research was published online in PNAS （www.pnas.org/doi/10.1073/pnas.2320331121）on April 9, 2024.