Recursively positive and negative chemotaxis coupling with reaction kinetics in self-organized inanimate motion

Oscillatory Motion of an Organic Droplet Reflecting a Reaction Scheme

“…On the basis of the experimental results and related papers, − ,,− we discuss the mechanism of oscillatory motion, including back-and-forth motion, depending on the pH.…”

“…15−22 Notably, we succeeded in inducing spontaneous spatiotemporal order in self-propulsion, such as oscillatory, synchronized, spatiotemporal collective motion, and the bifurcation of motion. [15][16][17][18][19][20][21][22]24,25 Many self-propelled objects, of which the driving force of motion originates from the difference in the interfacial tension around the objects, have been investi-gated. 15,17,21,23−25 The energy sources for most of these objects are initially contained within the objects themselves and are directly released on the surrounding surface.…”

“…Self-propelled objects, including bacteria, have been extensively studied because of their ability to transport materials or themselves within confined spaces. − Most inanimate self-propelled objects exhibit random or unidirectional motion, typically determined by their initial conditions. Alternatively, the direction and speed of motion can be controlled by an external field, such as an electromagnetic field. − In contrast, animate-like self-propelled objects can induce characteristic motion features while actively responding to their environment. − These observations indicate that the level of autonomy and diversity of self-propelled objects are greater than those of classical objects. − …”

“…Mimicking the mechanism of energy transduction in self-propelled objects, which can modify and respond to their immediate surroundings, has emerged as a strategy for enhancing the autonomy and diversity of self-propulsion. This approach is rooted in the field of nonlinear science. − Notably, we succeeded in inducing spontaneous spatiotemporal order in self-propulsion, such as oscillatory, synchronized, spatiotemporal collective motion, and the bifurcation of motion. − ,, Many self-propelled objects, of which the driving force of motion originates from the difference in the interfacial tension around the objects, have been investigated. ,,,− The energy sources for most of these objects are initially contained within the objects themselves and are directly released on the surrounding surface.…”

“…A higher oscillatory motion frequency corresponds to a shorter period of the resting state during oscillatory motion (Figure , S1, and b). The increase in the oscillatory motion frequency with an increase in pH when pH < p K a suggests that the hydrolysis of TA proceeds owing to the higher concentration of OH – ; the concentration of TOH around the droplet reaches a critical value for changing the rapid acceleration from the resting state. , In contrast, the decrease in the frequency of oscillatory motion with an increase in pH when pH > p K a suggests that a longer time is required to reach the critical value because TO – is the principal reaction product (Figure ). Thus, the frequency of oscillatory motion is the maximum at approximately pH = p K a (Figure ).…”