Wetting Behavior of Surface Nanodroplets Regulated by Periodic Nanostructured Surfaces

Abstract

Surfaces with nanostructure patterning are broadly encountered in nature, and they play a significant role in regulating various phenomena such as phase transition at the liquid/solid interface. Here, we designed two kinds of template substrates with periodic nanostructure patterns [i.e., nanotrench (NT) and nanopore (NP)]. Surface nanodroplets produced on these nanostructure surfaces were characterized to acquire their morphology and wetting properties. We show that nanostructure patterning could effectively regulate the shape, contact radius, and nucleate site of nanodroplets. While nanodroplets on the NT structure are constrained in one dimension, nanodroplets on the NP structure have enhanced the wetting property with constraints from two dimensions. Further numerical analysis indicates that the morphology and contact angles of nanodroplets on the NT structure depend on the substrate wettability and the droplet volume. These observations demonstrate how physical geometry and chemical heterogeneity of a substrate surface affect the growth and spreading of surface nanodroplets, which deepens our understanding on nanoscale phase separation.

Sequential droplet reactions for surface-bound gold nanocrater array

“…Hence both the concentration and the sequence of the reactants in the surrounding can be controlled by the flow of reactant solutions. Although on-droplet reactions have been reported for extraction and sensitive chemical analysis, [29] and for one-step synthesis of the precursor structures [1,34,35], the potential for sequential reactions of stable femtoliter droplets remains to be explored for synthesis of a wide range of surface-bound catatlytic nanomaterials.…”

Growth Rates of Hydrogen Microbubbles in Reacting Femtoliter Droplets

“…The mass flux between the droplets into the surrounding phase also plays an important role in the droplet reaction kinetics. , In this regard, femtoliter droplets immobilized on a solid surface have been used as a model system for the quantitative study of droplet reaction rates. Because the three-phase contact line of surface droplets is pinned by the solid surface, these droplets are stable on the substrate as the reactant is supplied in a controlled flow. − The volume of surface droplets is conveniently controlled by the solvent exchange method . The enhanced gas production rate in smaller surface droplets has recently been revealed by the growth rate of hydrogen nanobubbles as the product .…”

A Superhydrophilic Silicon Surface Enhanced by Multiscale Hierarchical Structures Fabricated by Laser Direct Writing

“…Surface wetting behavior has an important impact on the production, processing, and practical applications of materials. − In the fields of filtration, , penetration, , metal lubrication, and drug release, water is required to infiltrate and spread when contacting with a surface to achieve a hydrophilic effect. A surface constructed by multiscale hierarchical structures can significantly improve the wetting performance and attract increased attention from the academic community. − The mechanism has also been analyzed and confirmed in the Cassie–Baxter impregnating wetting model theory.…”