Asymmetric Nanoparticle May Go Active at Room Temperature

TL;DR

This study demonstrates through molecular dynamics simulations that asymmetrically shaped nanoparticles can spontaneously exhibit active, curved trajectories at room temperature due to imbalance forces from solvent collisions, akin to active matter behavior.

Contribution

The paper introduces a new physical mechanism for active motion in nanoparticles caused by shape asymmetry and solvent interactions, supported by theoretical formulas.

Findings

Nanoparticles exhibit spontaneous curved trajectories in dilute solutions.

The motion is driven by imbalance of collision forces from solvent molecules.

Theoretical models accurately describe the observed non-zero forces and trajectories.

Abstract

Using molecular dynamics simulations, we show that an asymmetrically shaped nanoparticle in dilute solution possesses a spontaneously curved trajectory within finite time interval, instead of the generally expected random walk. This unexpected dynamic behavior has a similarity to that of active matters, such as swimming bacteria, cells or even fishes, but is of a different physical origin. The key to the curved trajectory lies in the non-zero resultant force originated from the imbalance of the collision forces acted by surrounding solvent molecules on the shaped nanoparticle during its orientation regulation. Theoretical formulae based on the microscopic observation have been derived to describe this non-zero force and the resulted motion of the nanoparticle.