Effects of dissimilar molecular interface and ion-concentration on wetting characteristics of nanodroplets

M Masuduzzaman and B Kim, MICROFLUIDICS AND NANOFLUIDICS, 25, 54 (2021).

DOI: 10.1007/s10404-021-02455-6

Measurements of contact angles are conventionally used to describe the wetting behavior of nanoscopic liquid droplets on a flat substrate, where the dissimilar molecular interface is vague. Considering this issue, we performed an atomistic simulation of the spherical nano- droplets of pure and ion-water on a bare solid substrate to determine the relationship between the contact angle and the boundary position residing at the solid-liquid interface. In this exploration, the existence of the correlation between the contact angle and the associated boundaries is observed using classical Young's equation. Our study reveals that the effects of the variable wettability and boundary positions have a significant impact on the contact angle. In addition, we investigate the contact angle based on boundary positions for different ion-water nano-droplets with varying ion concentrations. Interestingly, the contact angles of pure and ion-water droplets are almost identical in a specific boundary position for both varying wettability and ion concentrations. Finally, we compare the estimated contact angle for different boundary positions with the solid substrate experimental contact angle. Atomistic simulations indicate that the interfacial boundary concept for measuring contact angle using classical Young's equation gives a certain convergence to experimental evaluation.

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