Using molecular dynamics simulations, we demonstrate pumping of water through a carbon nanotube by applying the combination of a rotating electric field and a rotating magnetic field. The driving force is a Lorentz force generated from the motion of charges in the magnetic field, and the motion is caused by the rotation of the electric field. We find that there exits a linear relationship between the average pumping velocity v and magnetic field strength B, which can be used to control the flux of the continuous unidirectional water flow. This approach is expected to be used in liquid circulation without a pressure gradient.

The formation of gas bubbles by submerged orifices is a fundamental process encountered in various industrial applications. The dynamics of the contact line and the contact angle may have a significant influence on the detached bubble size depending on the wettability of the system. In this study, the influence of wetting conditions on the dynamics of bubble formation from a submerged orifice is investigated experimentally and numerically. The experiments are performed using a hydrophobic orifice plate and a series of ethanol-water solutions to vary the wettability where the key characteristics of the bubbles are measured using a high-speed, high-resolution camera. An extensive analysis on the influence of wetting conditions on the bubble size, bubble growth mechanism and the behavior of the contact line is given. Bubble growth stages, termed (1) hemispherical spreading, (2) cylindrical spreading, (3) critical growth and (4) necking, are identified based on key geometrical parameters of the bubble and relevant forces acting on the bubble during the growth. The experimental results show that the apparent contact angle varies in a complicated manner as the bubble grows due to the surface roughness and heterogeneity. The experimental findings are finally used to validate the local front reconstruction method with a contact angle model to account for the contact angle hysteresis observed in the experiments.

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