Emerging Applications of Superhydrophilic‐Superhydrophobic Micropatterns

Abstract

Water on superhydrophilic surfaces spreads or is absorbed very quickly, and exhibits water contact angles close to zero. We encounter superhydrophilic materials in our daily life (e.g., paper, sponges, textiles) and they are also ubiquitous in nature (e.g., plant and tree leaves, Nepenthes pitcher plant). On the other hand, water on completely non-wettable, superhydrophobic surfaces forms spherical droplets and rolls off the surface easily. One of the most well-known examples of a superhydrophobic surface is the lotus leaf. Creating novel superhydrophobic surfaces has led to exciting new properties such as complete water repellency, self-cleaning, separation of oil and water, and antibiofouling. However, combining these two extreme states of superhydrophilicity and superhydrophobicity on the same surface in precise two-dimensional micropatterns opens exciting new functionalities and possibilities in a wide variety of applications from cell, droplet, and hydrogel microarrays for screening to surface tension confined microchannels for separation and diagnostic devices. In this Progress Report, we briefly describe the methods for fabricating superhydrophilic-superhydrophobic patterns and highlight some of the newer and emerging applications of these patterned substrates that are currently being explored. We also give an outlook on current and future applications that would benefit from using such superhydrophilic-superhydrophobic micropatterns.

External‐Field‐Induced Gradient Wetting for Controllable Liquid Transport: From Movement on the Surface to Penetration into the Surface

“…To overcome this problem, the cooperative effect of the external field and surface microstructure provides the possibility for partial entry of the liquid into the film, and the corresponding transition of the wettability and adhesion, resulting in the liquid patterning. [3,5] In this section, liquid patterning on surfaces induced by an external field (light and photoelectric cooperation) is mainly discussed; other stimuli-induced transitions of the wettability and adhesion that are promising for this field are also briefly introduced.…”

“…[1][2][3][4][5][6][7][8] The liquid-wetting behavior on a solid or liquid surface is mainly dependent on the chemical composition and surface roughness, which play important roles in liquid transport. [9][10][11][12][13][14][15][16] The wettability gradient of a surface for a liquid droplet with an asymmetrical contact angle (CA) can produce a driving force for liquid motion, which is generally generated by introducing a chemical or structure gradient.…”

Robust superhydrophilic patterning of superhydrophobic ormosil surfaces for high-throughput on-chip screening applications

“…[7][8][9][10][11][12] In addition, precise control of the wetted and non-wetted patterns on a single surface allows the formation of ordered droplet arrays and easy droplet manipulation as well as immobilization and aliquoting of droplet-dispersed materials including nanoparticles, biomolecules and cells. 13,14 Therefore, patterned superhydrophobic surfaces have attracted signicant research interest for high-throughput biological and chemical screening. [15][16][17][18] Over the past decade, a number of successful methods have been introduced to prepare superhydrophilicsuperhydrophobic micropatterns including photo-induced chemical modication, [18][19][20][21][22] plasma treatment, 4,[23][24][25] inkprinting, 6,26-28 direct laser writing 29 and photo-catalytic decomposition.…”

Maskless, High‐Precision, Persistent, and Extreme Wetting‐Contrast Patterning in an Environmental Scanning Electron Microscope

“…Small. doi:10.1002/smll.201503127, which Since the past decade, micro-and nanopatterns with high wetting contrast for water have been reported on natural [1,2] and man-made [3,4] surfaces. Such patterns have found uses in a diverse set of applications, including water collection from humid air mimicking desert beetles; [5] enhancing boiling heat transfer; [6] microelectromechanical systems (MEMS) assembly using surface tension-driven self-alignment; [7] arranging nanostructures in ordered arrays [8] for 2 nanophotonic devices e.g.…”