Superfast nanodroplet propulsion in 2D nanochannels tuned by strain gradients

Directional transport of droplets is crucial for industrial applications and chemical engineering processes, with significant potential demonstrated in water harvesting, microfluidics, and heat transfer. In this work, we present a novel approach to induce self-driving behavior in nanodroplets within a two-dimensional (2D) nanochannel using a strain gradient, as demonstrated through molecular dynamics simulations. Our findings reveal that a small strain gradient imposed along a nanochannel constructed by parallel surfaces can induce water transport at ultrafast velocities (O(10² m s^-1)), far exceeding macroscale predictions. Certainly, a larger strain gradient further enhances droplet transport velocity. Additionally, combining a strain gradient with nonparallel surfaces results in up to a 150% increase in transport efficiency. Furthermore, we show that this spontaneous transport mechanism is applicable to nanochannels composed of various 2D materials and successfully establish a reliable theoretical model. These simulation results provide new insights into the directional transport of nanodroplets in 2D nanochannels, opening avenues for advanced applications in nanotechnology and fluid dynamics.