Precise Droplet Manipulation Based on Surface Heterogeneity

Abstract

ConspectusThe control of droplet behavior has been investigated for several centuries due to its universality and significance in nature, daily life, and industrial applications. Diverse strategies have been developed and employed to regulate droplet behavior, and great progress has been achieved such as accelerated droplet bouncing, controlled droplet dispensing, and enhanced droplet adhesion. Compared with the strategies utilizing external fields including magnets, heat, light, and electricity as well as various topological structures, the heterogeneous wettability surface provides a facile and efficient way to manipulate droplet behavior and thus has aroused increasing research interest in many fields.The heterogeneous wettability substrate integrates wettable and less wettable regions onto an individual surface, with rational design and a geometrical arrangement. Therefore, it shows more precise, diverse, and controllable interactions with droplets than homogeneous surfaces. In addition to confining the droplet position and morphology and regulating the droplet dynamics, the nonuniformity in wettability can induce a difference in electrical conductivity, nucleation energy barriers, and so forth, which greatly extends its application in the fields of functional materials deposition and device fabrication. In this Account, recent progress in the precise droplet manipulation based on heterogeneous wettability is summarized. First, the principle of droplet control by a heterogeneous surface and the development of the green printing technique based on this principle are introduced. Then the droplet manipulation, categorized as droplet patterning, droplet isolation, and droplet dynamics, is described. Meanwhile, related applications, such as high-capacity information coding, highly sensitive detection, and high-performance optic/electric device fabrication, are demonstrated. In addition, the general principle for controlling the droplet impact using heterogeneous wettability substrates is highlighted. Finally, a brief summary of this Account, with challenges and opportunities in this field, is proposed.