Ultrasmall Liquid Droplets on Solid Surfaces: Production, Imaging, and Relevance for Current Wetting Research

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2009-06, Vol.5 (12), p.1366-1390
• Main Authors: Méndez-Vilas, Antonio, Jódar-Reyes, Ana Belén, González-Martín, María Luisa
• Format: Article
• Language: English
• Subjects: atomic force microscopy; environmental scanning electron microscopy; fluid interfaces; imaging; Imaging, Three-Dimensional - methods; Particle Size; Surface Properties; Water - chemistry; Wettability; wetting
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.200800819

The investigation of micro‐ and nanoscale droplets on solid surfaces offers a wide range of research opportunities both at a fundamental and an applied level. On the fundamental side, advances in the techniques for production and imaging of such ultrasmall droplets will allow wetting theories to be tested down to the nanometer scale, where they predict the significant influence of phenomena such as the contact line tension or evaporation, which can be neglected in the case of macroscopic droplets. On the applied side, these advances will pave the way for characterizing a diverse set of industrially important materials such as textile or biomedical micro‐ and nanofibers, powdered solids, and topographically or chemically nanopatterned surfaces, as well as micro‐and nanoscale devices, with relevance in diverse industries from biomedical to petroleum engineering. Here, the basic principles of wetting at the micro‐ and nanoscales are presented, and the essential characteristics of the main experimental techniques available for producing and imaging these droplets are described. In addition, the main fundamental and applied results are reviewed. The most problematic aspects of studying such ultrasmall droplets, and the developments that are in progress that are thought to circumvent them in the coming years, are highlighted. Wetting: The current interest in advancing the knowledge of the behavior of ultrasmall droplets (see image; courtesy of Dr. Luis Labajos‐Broncano) on solid surfaces in a variety of different fields and applications is highlighted. The achievements in the field are reviewed and the technical advances that are thought to circumvent the current limitations in the coming years are discussed.