Unidirectional Liquid Manipulation Via an Integrated Mesh with Orthogonal Anisotropic Slippery Tracks

Abstract

The rational manipulation of fluid behavior by functional interfaces plays an indispensable role in the development of advanced materials and devices involving liquid/solid interactions. Previous examples of the liquid "diode" that allows fluid penetration in only one direction rely mainly on the remarkable wettability gradient/contrast. Inspired by the wetting phenomena of the rice leaf and the Pitcher plant, an integrated mesh with orthogonal anisotropic slippery tracks (IMOAS) is presented here that can realize similar unidirectional droplet penetration using a distinct mechanism. The unidirectional droplet penetration can be conveniently switched via the 90° rotation of the IMOAS, showing a highly controllable liquid manipulation. The droplet tends to slip on the surface, which can maximize the contact area between the liquid and the tracks, and complies with the principle of the lowest surface energy. Based on this unique liquid controlling strategy, droplet manipulation of the IMOAS during fog harvesting and droplet self-regulation has been conducted to illustrate its potential applications. The current design could aid the understanding of liquid unidirectional penetration and unlock additional possibilities for the optimization of fluidrelated systems.

Highly Flexible Monolayered Porous Membrane with Superhydrophilicity–Hydrophilicity for Unidirectional Liquid Penetration

“…Directional transport of liquid is a common phenomenon in nature and in humans’ life ability. − Manipulation of liquid transport in a specific direction inspires the development of fluidic devices for various applications ranging from moisture wicking technology , to fluid manipulation. − In accustomed transportation, liquid can be continuously transported by using external forces, while in nature, many creatures obtain directional liquid transport ability through various unique anisotropic interfaces. − For example, water droplets could be continuously unidirectional transported on the surface of spider silk by its asymmetric structure, − and similar phenomenons are also widely discovered in beetle skin, , the nepenthes, long-mouthed beaks, cactus branches, etc . , Therefore, constructing an asymmetric surface structure may be an efficient method for directional liquid transport. − …”

Smart Control for Water Droplets on Temperature and Force Dual-Responsive Slippery Surfaces

“…9−13 For instance, Cao et al demonstrate that the orthogonal assembly of anisotropic tracks can realize unidirectional droplet manipulation by fusing the bioinspirations of the rice leaf and the pitcher plant. 13 Levkin et al construct patterned slippery surfaces for precisely positioning and guiding the droplets up to volumes of several microliters. 14 Usually, these approaches can be classified into the same category that relies on the assistance of Laplace pressure arising from the asymmetry of droplet shape caused by the substrate's morphology.…”

“…Liquid droplet manipulations, such as droplet storage, transfer, and mixing, have garnered widespread attention because of their potential applications in cell screening, biochemical synthesis, and molecular sensing. − Generally, most functional surfaces for droplet manipulations can be categorized into superhydrophobic surfaces , and slippery lubricant-infused porous surfaces (SLIPSs) based on the special interaction among multiple phases. , As an emerging functional surface inspired by the Nepenthes pitcher plant, SLIPS shows excellent nonselective liquid repellency and a low hysteresis feature (<5°) and has attracted considerable interest in the field of interfacial science and related applications such as drag reduction, antifouling, anti-icing, and bubble and droplet manipulation. − For instance, Cao et al demonstrate that the orthogonal assembly of anisotropic tracks can realize unidirectional droplet manipulation by fusing the bioinspirations of the rice leaf and the pitcher plant . Levkin et al construct patterned slippery surfaces for precisely positioning and guiding the droplets up to volumes of several microliters .…”

Inner surface of Nepenthes slippery zone: ratchet effect of lunate cells causes anisotropic superhydrophobicity

“…Most insects find the highly evolved slippery zone has considerably unique slippage properties, that execute the function of retaining prey [11]. In recent years, both the morphology/structure and the predation function of the slippery zone have gradually attracted a large number of investigations, attempting to establish bionic prototypes for developing insect slippery trapping plates [10,[12][13][14][15] and other bioinspired materials with anti-adhesive properties [16][17][18][19][20][21].…”