  Pinning of liquid droplets on solid substrates is ubiquitous and plays an
essential role in many applications, especially in various areas, such as
microfluidics and biology. Although pinning can often reduce the efficiency of
various applications, a deeper understanding of this phenomenon can actually
offer possibilities for technological exploitation. Here, by means of molecular
dynamics simulation, we identify the conditions that lead to droplet pinning or
depinning and discuss the effects of key parameters in detail, such as the
height of the physical pinning-barrier and the wettability of the substrates.
Moreover, we describe the mechanism of the barrier crossing by the droplet upon
depinning, identify the driving force of this process, and, also, elucidate the
dynamics of the droplet. Not only does our work provide a detailed description
of the pinning and depinning processes, but it also explicitly highlights how
both processes can be exploited in nanotechnology applications to control
droplet motion. Hence, we anticipate that our study will have significant
implications for the nanoscale design of substrates in micro and nano-scale
systems and will assist with assessing pinning effects in various applications.
