Nanomotor dynamics in a chemically oscillating medium

Abstract

Synthetic nanomotors powered by chemical reactions have potential uses as cargo transport vehicles in both in vivo and in vitro applications. In many situations, motors will have to operate in out-of-equilibrium complex chemically reacting media, which supply fuel to the motors and remove the products they produce. Using molecular simulation and mean-field theory, this paper describes some of the new features that arise when a chemically powered nanomotor, operating through a diffusiophoretic mechanism, moves in an environment that supports an oscillatory chemical reaction network. It is shown how oscillations in the concentrations in chemical species in the environment give rise to oscillatory motor dynamics. More importantly, since the catalytic reactions on the motor that are responsible for its propulsion couple to the bulk phase reaction network, the motor can change its local environment. This process can give rise to distinctive spatiotemporal structures in reaction-diffusion media that occur as a result of active motor motion. Such locally induced nonequilibrium structure will play an important role in applications that involve motor dynamics in complex chemical media.

Damping and clustering into crowded environment of catalytic chemical oscillators

“…We show that, as previously reported [46], the effect of the introduction of catalytic obstacles in a system with a complex oscillating chemical reaction is to reduce the oscillations in it, leading the system to a fixed point where the limit cycles are shifted. Additionally, we fit these oscillations to a damped periodic function, finding that its decay constant γ scales linearly with the volume fraction occupied by the obstacles (φ) after a certain amount of obstacles is introduced; meaning that there exists a critical damping value for φ.…”

Self-propulsion and interactions of catalytic particles in a chemically active medium

“…In an inert environment, the medium itself neither creates nor destroys the substrate required for the machines’ catalytic behavior. However, molecular dynamics simulations have shown that the chemical activity of the underlying environment may alter diffusiophoresis [25, 26]. Those simulations illustrate that background chemical activity can reduce the self-propulsion speed [25].…”

Control of active polymeric filaments by chemically-powered nanomotors

“…By periodically varying the chemical constraints cyclic expansion and contraction of the gel-like filament states was obtained, which are reminiscent of the similar states in oscillating hydrogels activated by the Belousov-Zhabotinsky reaction. If the fluid phase reactions that control the nonequilibrium state can sustain oscillations and couple to the motor reactions 43 , then autonomous control of the filament oscillations could also be achieved.…”