Surface-Tension-Confined Channel with Biomimetic Microstructures for Unidirectional Liquid Spreading.

Yi Zhang,Yang Gan,Huawei Chen,Liwen Zhang,Deyuan Zhang

doi:10.3390/mi11110978

Yi Zhang, Yang Gan + Show 3 more

Open Access

https://doi.org/10.3390/mi11110978

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Abstract

Unidirectional liquid spreading without energy input is of significant interest for the broad applications in diverse fields such as water harvesting, drop transfer, oil–water separation and microfluidic devices. However, the controllability of liquid motion and the simplification of manufacturing process remain challenges. Inspired by the peristome of Nepenthes alata, a surface-tension-confined (STC) channel with biomimetic microcavities was fabricated facilely through UV exposure photolithography and partial plasma treatment. Perfect asymmetric liquid spreading was achieved by combination of microcavities and hydrophobic boundary, and the stability of pinning effect was demonstrated. The influences of structural features of microcavities on both liquid spreading and liquid pinning were investigated and the underlying mechanism was revealed. We also demonstrated the spontaneous unidirectional transport of liquid in 3D space and on tilting slope. In addition, through changing pits arrangement and wettability pattern, complex liquid motion paths and microreactors were realized. This work will open a new way for liquid manipulation and lab-on-chip applications.

Highlights

Unidirectional liquid spreading has attracted worldwide attention due to its extensive application prospect in diverse fields, such as water harvesting [1,2,3], self-lubrication [4], liquid separation [5], and microfluidic operation [6,7,8]
In order to reduce the complexity in manufacturing the multilevel structures of artificial peristome surfaces, we proposed a simple method to construct the unidirectional liquid spreading channel that combines the striped wettability pattern and microstructures as shown in Figure 1b, where W is the width of hydrophilic stripe
The liquid spreads unidirectionally along the hydrophilic stripe until a slender liquid trip is formed, and the rear side of liquid remains static throughout the second flow regime (Figure 2b)

Summary

Introduction

Unidirectional liquid spreading has attracted worldwide attention due to its extensive application prospect in diverse fields, such as water harvesting [1,2,3], self-lubrication [4], liquid separation [5], and microfluidic operation [6,7,8]. The existing liquid manipulation methods induced by external driving fields are gradually unable to meet the requirements of green, efficient and portable microfluidic devices [9,10,11]. Different strategies have been proposed to break the equilibrium state of droplet on surfaces and achieve self-driven asymmetric spreading. The limited transport distance and relatively simple transport route are far from what would be demanded for practical applications

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