Molecular Dynamics Simulation of Nanoforces between Substrates Mediated by Liquid Bridges: Controlling Separation and Force Fluctuations

Abstract

Molecular dynamics simulations allow determination of the force between a tip and a sample mediated by a fluid or a nanoscale capillary bridge at any separation distance in approach−retract cycles. However, without further consideration, the procedure leads to force−distance curves without control of tip-to-sample distance and tip oscillations. Here we show that the solution of a macroscopic model describing the dynamics of the tip−sample interaction can precisely guide the choice of optimum parameters, for instance, tip elastic constant and approach speed, for controlled simulations. The method is applied to the interaction between two substrates in two cases of intervening fluid: a water bridge and a Lennard-Jones bridge. The method can be very useful in the determination of force−distance curves in more complex systems.

Computer Simulation of the Effect of Wetting Conditions on the Solvation Force and Pull-Off Force of Water Confined between Two Flat Substrates

“…The tip of this system is formed by S2. The tip is moved by displacing the top sites of the SP with constant speed; the dynamics of this system has been studied previously . The pull-off simulation is analogous to an AFM experiment.…”

Nucleation of Capillary Bridges and Bubbles in Nanoconfined CO2

“…Capillary processes are at the center of a wide range of phenomena, including the onset of phase transitions in confined geometries, − the control of friction between sliding surfaces, − or the formation of capillary liquid bridges during inflammatory processes of the lungs. , These fluid contacts can actually take place over vastly different length scales and have been reported for colloidal systems − and in nanotribology and nanolithography. − Recent advances on the theoretical front have led to the extension of capillary theory (CT), whose tenets are rooted in a macroscopic approach, to nanoscopic systems by connecting the free energy barrier of nucleation for the fluid contacts to the contributions arising from the surface tension …”

Roughness Effect on the Pull-Off Force between Two Surfaces with Water Adsorbed between Them. A Molecular Dynamics Simulation Perspective

“…Figure shows a general diagram of the system, which allows both the force law and pull-off force to be determined. The force laws are obtained according to the method developed in refs and . The pull-off simulations are performed according to ref .…”

“…The SP is formed by 576 springs. The simulations are performed with a program that has been used in previous works. ,, The water temperature is controlled at 298 K. The solid S1 and S2 in this system do not interact through electrostatic forces, F E = 0. They do not form chemical bonding at the contact point, F B = 0.…”