Spreading of a distilled water droplet over polished and laser-treated aluminum surfaces

Spreading of a distilled water droplet over polished and laser-treated aluminum surfaces is studied experimentally. We present an attempt to apply the molecular-kinetic theory to the experimental dependences of the dynamic contact angle on the contact line speed. Advancing and receding contact angles at different liquid flow rates are obtained experimentally, and their values are used to calculate the contact angle hysteresis on each substrate. The bottom-up approach is used to form a droplet on the surface when liquid is supplied through an opening in the substrate. This makes it possible to control wetting and dewetting by increasing and decreasing the droplet volume. The main geometrical parameters are obtained using the shadow method by Axisymmetric Drop Shape Analysis-Profile. Experimental data on the dynamic contact angle on a laser-treated surface are found to be a better fit to the theoretical equation in comparison with the results on a smooth polished surface. We have formulated a hypothesis that the theoretical and experimental values of the dynamic contact angle are in good agreement due to the physics of the process (smaller hysteresis on the laser-treated surface).