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3D Printing of Overhanging Microstructures for Tunable Liquid Wettability

Xiaojiang Liu^1,*, Zhongze Gu¹, Kun Zhou²

1 State Key Laboratory of Digital Medical Engineering, School of Biological Science and Medical Engineering, Southeast University, 2 Southeast University Road, Nanjing, 211189, China
2 Singapore Centre for 3D Printing, School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Ave, 639798, Singapore

* Corresponding Author: Xiaojiang Liu. Email:

The International Conference on Computational & Experimental Engineering and Sciences 2024, 29(3), 1-2. https://doi.org/10.32604/icces.2024.011320

Abstract

Surfaces with overhanging microstructures play an essential role in surface wettability. Typically, surfaces with tightly-distributed multiply symmetric re-entrant microstructures enable the liquid suspension toward water, oil, and even n-perfluorooctane, whose surface tension is as low as 12.0 mN/m [1-4]. In contrast, surfaces with asymmetric re-entrant microstructures are favorable for unidirectional liquid spreading, where the liquids exhibit a small contact angle on the surfaces [5]. These fantastic wettability behaviors can be attributed to three-dimensional (3D) features of the overhanging microstructures, where the edge effect and Laplace pressure difference are generated on the overhanging microstructures. Based on these re-entrant microstructures, multiple functions have been realized. One typical example is the ultra-wide-angle transport based on asymmetric re-entrant microstructures, which can achieve high transport efficiency and programmable forward/lateral transport paths simultaneously. Herein, the wetting mechanisms behind these overhanging microstructures are discussed, and the intricate microstructures are constructed by 3D/4D printing techniques based on two-photon polymerization (TPP) and digital light processing (DLP). The TPP-based 3D/4D printing enables the manufacturing of 3D parts with sub-micrometer resolution but at a low speed, while the DLP-based 3D/4D printing enables the manufacturing of 3D parts at a relatively high speed but with sub-millimeter resolution. Therefore, the printing technique is carefully selected to fabricate the target surfaces for tunable liquid wettability.

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Keywords

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