Droplet Control Based on Pinning and Substrate Wettability

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 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
also it explicitly highlights how both processes can be exploited
in nanotechnology applications to control the droplet motion. Hence,
we anticipate that our study will have significant implications for
the nanoscale design of substrates in micro- and nanoscale systems
and will assist with assessing pinning effects in various applications.