Oscillation of a Polymer Gel Entrained with a Periodic Force

The oscillation of a polymer gel induced by the Belousov–Zhabotinsky (BZ) reaction was investigated under an external force composed of a square wave. The oscillation of the BZ reaction entrained to the periodic force and the features of this entrainment changed depending on the period and duty cycle of the square wave. The experimental results suggest that the change in the volume of the gel also gave feedback to the BZ reaction. The mechanism of entrainment is discussed in relation to the compression of the gel and the reaction–diffusion system in the BZ reaction

Oscillatory Motion of an Organic Droplet Reflecting a Reaction Scheme

An organic droplet containing thymol acetate (TA) floating on a sodium dodecyl sulfate aqueous phase was examined to develop a novel self-propelled object based on reaction kinetics. Two types of oscillatory motion, without back-and-forth motion (Osc I) and with back-and-forth motion (Osc II), were observed by varying the pH of the aqueous phase. The oscillation frequency reached its maximum at pH 9.6, coinciding with the occurrence of Osc II. The kinetics of the hydrolysis of TA as a reactant and the acid–base equilibrium between thymol (TOH) and the thymolate ion (TO–) as products were evaluated experimentally. The driving force of motion was discussed on the basis of the interfacial tension. The pH dependence of the oscillation frequency and the selection of Osc I or II were attributed to the equilibrium between the TOH and TO–. These results highlight the possibility of designing self-propulsion systems by considering reaction kinetics and chemical properties

Periodic Reciprocating Motion of a Polymer Gel on an Aqueous Phase Synchronized with the Belousov–Zhabotinsky Reaction

A self-oscillating gel induced by the Belousov–Zhabotinsky (BZ) reaction was investigated on an aqueous phase. When the Ru-catalyst in the gel was rapidly oxidized, the gel was accelerated in a direction opposite to the side of oxidation. The gel then returned to its original position while the Ru-catalyst in the gel was slowly reduced. To clarify the mechanism of this periodic reciprocation of the gel, the contact angle between a sessile bubble and the gel and the time-variation of the adhesive force of the gel on the aqueous phase were measured. The experimental results suggest that the periodic reciprocation of the gel is driven by the periodic change in the contact angle of the gel induced by the BZ reaction

Distinguishing the Dynamic Fingerprints of Two- and Three-Dimensional Chemical Waves in Microbeads

Spatiotemporal oscillations confined to quasi-2D surface layers or 3D volumes play an important role for wave-based information relay and global oscillations in living systems. Here, we describe experiments with the Belousov–Zhabotinsky reaction confined to microbeads, in which the catalyst is selectively loaded either onto the surface or into the body of the spherical beads. We find that the dynamics of global oscillations, traveling reaction fronts, and rotating spiral waves under surface confinement are strikingly different from those in the bead volume. Our results establish a useful model system for the study of geometrical effects on nonlinear chemical processes and provide diagnostic features that allow the distinction of membrane-mediated 2D and cytosolic 3D processes in biological cells

Oscillatory Motion of an Organic Droplet Reflecting a Reaction Scheme

An organic droplet containing thymol acetate (TA) floating on a sodium dodecyl sulfate aqueous phase was examined to develop a novel self-propelled object based on reaction kinetics. Two types of oscillatory motion, without back-and-forth motion (Osc I) and with back-and-forth motion (Osc II), were observed by varying the pH of the aqueous phase. The oscillation frequency reached its maximum at pH 9.6, coinciding with the occurrence of Osc II. The kinetics of the hydrolysis of TA as a reactant and the acid–base equilibrium between thymol (TOH) and the thymolate ion (TO–) as products were evaluated experimentally. The driving force of motion was discussed on the basis of the interfacial tension. The pH dependence of the oscillation frequency and the selection of Osc I or II were attributed to the equilibrium between the TOH and TO–. These results highlight the possibility of designing self-propulsion systems by considering reaction kinetics and chemical properties

Oscillatory Motion of an Organic Droplet Reflecting a Reaction Scheme

An organic droplet containing thymol acetate (TA) floating on a sodium dodecyl sulfate aqueous phase was examined to develop a novel self-propelled object based on reaction kinetics. Two types of oscillatory motion, without back-and-forth motion (Osc I) and with back-and-forth motion (Osc II), were observed by varying the pH of the aqueous phase. The oscillation frequency reached its maximum at pH 9.6, coinciding with the occurrence of Osc II. The kinetics of the hydrolysis of TA as a reactant and the acid–base equilibrium between thymol (TOH) and the thymolate ion (TO–) as products were evaluated experimentally. The driving force of motion was discussed on the basis of the interfacial tension. The pH dependence of the oscillation frequency and the selection of Osc I or II were attributed to the equilibrium between the TOH and TO–. These results highlight the possibility of designing self-propulsion systems by considering reaction kinetics and chemical properties

Oscillatory Motion of an Organic Droplet Reflecting a Reaction Scheme

An organic droplet containing thymol acetate (TA) floating on a sodium dodecyl sulfate aqueous phase was examined to develop a novel self-propelled object based on reaction kinetics. Two types of oscillatory motion, without back-and-forth motion (Osc I) and with back-and-forth motion (Osc II), were observed by varying the pH of the aqueous phase. The oscillation frequency reached its maximum at pH 9.6, coinciding with the occurrence of Osc II. The kinetics of the hydrolysis of TA as a reactant and the acid–base equilibrium between thymol (TOH) and the thymolate ion (TO–) as products were evaluated experimentally. The driving force of motion was discussed on the basis of the interfacial tension. The pH dependence of the oscillation frequency and the selection of Osc I or II were attributed to the equilibrium between the TOH and TO–. These results highlight the possibility of designing self-propulsion systems by considering reaction kinetics and chemical properties

Periodic Reciprocating Motion of a Polymer Gel on an Aqueous Phase Synchronized with the Belousov–Zhabotinsky Reaction

A self-oscillating gel induced by the Belousov–Zhabotinsky (BZ) reaction was investigated on an aqueous phase. When the Ru-catalyst in the gel was rapidly oxidized, the gel was accelerated in a direction opposite to the side of oxidation. The gel then returned to its original position while the Ru-catalyst in the gel was slowly reduced. To clarify the mechanism of this periodic reciprocation of the gel, the contact angle between a sessile bubble and the gel and the time-variation of the adhesive force of the gel on the aqueous phase were measured. The experimental results suggest that the periodic reciprocation of the gel is driven by the periodic change in the contact angle of the gel induced by the BZ reaction

Distinguishing the Dynamic Fingerprints of Two- and Three-Dimensional Chemical Waves in Microbeads

Spatiotemporal oscillations confined to quasi-2D surface layers or 3D volumes play an important role for wave-based information relay and global oscillations in living systems. Here, we describe experiments with the Belousov–Zhabotinsky reaction confined to microbeads, in which the catalyst is selectively loaded either onto the surface or into the body of the spherical beads. We find that the dynamics of global oscillations, traveling reaction fronts, and rotating spiral waves under surface confinement are strikingly different from those in the bead volume. Our results establish a useful model system for the study of geometrical effects on nonlinear chemical processes and provide diagnostic features that allow the distinction of membrane-mediated 2D and cytosolic 3D processes in biological cells

Distinguishing the Dynamic Fingerprints of Two- and Three-Dimensional Chemical Waves in Microbeads

Spatiotemporal oscillations confined to quasi-2D surface layers or 3D volumes play an important role for wave-based information relay and global oscillations in living systems. Here, we describe experiments with the Belousov–Zhabotinsky reaction confined to microbeads, in which the catalyst is selectively loaded either onto the surface or into the body of the spherical beads. We find that the dynamics of global oscillations, traveling reaction fronts, and rotating spiral waves under surface confinement are strikingly different from those in the bead volume. Our results establish a useful model system for the study of geometrical effects on nonlinear chemical processes and provide diagnostic features that allow the distinction of membrane-mediated 2D and cytosolic 3D processes in biological cells