Time‐Programming, Clocking, and Self‐Oscillating Polymer Gels

In living systems, there are many autonomous and oscillatory phenomena to sustain life such as heart beating. “Self-oscillating” polymer gels that undergo spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli, as with heart muscle, were developed by the author's group. The self-oscillating gels were designed by utilizing the Belousov–Zhabotinsky (BZ) reaction, an oscillating reaction, as a chemical model of the TCA cycle. They have systematically studied these self-oscillating polymer gels since they were first reported in 1996. Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems such as biomimetic actuators, mass transport systems, and functional fluids. For example, it was demonstrated that an object was autonomously transported in the tubular self-oscillating gel by the peristaltic pumping motion similar to an intestine. Further, self-oscillating polymer brush surface like cilia, vesicles, or colloidosomes undergoing cell-like autonomous shape oscillations with buckling, was prepared. Besides, autonomous sol-gel oscillation and amoeba-like motion were realized utilizing well-designed block copolymer solution. In this article, recent progress on the self-oscillating polymer gels is summarized.