Thermally enhanced self-propelled droplet motion on gradient surfaces

Abstract

Droplet motion over a surface with wettability gradient has been simulated using molecular dynamics (MD) simulation to highlight the underlying physics. GROMACS and Visual Molecular Dynamics (VMD) were used for simulation and intermittent visualization of the droplet configuration respectively. The simulations mimic experiments in a comprehensive manner wherein micro-sized droplets are propelled by surface wettability gradient against a number of retarding forces. The liquid-wall Lennard-Jones interaction parameter and the substrate temperature were varied to explore their effects on the three-phase contact line friction coefficient. The contact line friction was observed to be a strong function of temperature at atomistic scales, confirming the experimentally observed inverse functionality between the coefficient of contact line friction and increase in temperatures. These MD simulation results were successfully compared with the results from a model for self-propelled droplet motion on gradient surfaces.

Numerical simulation of droplet impact on wettability-patterned surfaces

“…These two kinds of non-homogeneous surfaces allow for passive control of the droplet impact dynamics and can be designed to cause specific outcomes. As important -and relevant-as these surfaces are, studies of droplet impact on such surfaces in the computational realm [31] are rare, with very few numerical reports [32][33][34] addressing such non-uniform surfaces. For instance, in a the recent work Xu [35] et al studied numerically the droplet impact on an hydrophobic surface patterned with hydrophilic dots.…”

Drop transport and positioning on lubricant-impregnated surfaces

“…Such surfaces can be created by either introducing a gradient in the surface chemistry 12 or in the surface topography [13][14][15][16] . Drop transport can also be achieved by means of an external field, such as a gradient in temperature 17,18 , by applying an electric field [19][20][21] or using mechanical actuation [22][23][24][25] .…”

Coalescence of droplets on micro-structure patterned hydrophobic planar solid surfaces

“…A solid surface allows the implementation of droplet-based microuidic systems that handle droplets individually. The wettability change and motion inception of sessile droplets can be achieved using external forces such as chemical, 4 thermocapillarity, [5][6][7] lighting, 8,9 electrostatic, 10,11 and magnetic forces. 12,13 These active manipulations of droplets commonly require additional components, which increase the cost and complexity of the microuidic devices.…”