Controllable fabrication of periodic arrays of high-aspect-ratio micro-nano hierarchical structures and their superhydrophobicity

Abstract

This paper demonstrates a flexible and controllable fabrication of vertically aligned and high-aspect-ratio (HAR) micro-nano hierarchical structures using conventional micro-technologies. We first masked the nanopatterns on a photoresist mold by shifting the same photomask, which could be performed using conventional contact microlithography. Thereby replicating nanopatterns onto an aluminium mold and successfully fabricating silicon nanopillar arrays about 300 nm in diameter and 5 μm in height via the deep reactive etching (DRIE) process. We also fabricated micro-nano hierarchical structures with variable aspect ratios using the proposed nanopattern technology and DRIE process without using any special nanopatterning equipment or techniques. The proposed method not only simplified the fabrication process but also produced HAR (higher than 15) structures. We also investigate the replica molding steps from the fabricated silicon stamp to a UV-curable polymer replica using a PDMS mold and conventional nano-imprinting, where each nanopillar diameter was 320 nm with 95% fidelity. As a result, the hierarchical structure arrays show stable superhydrophobic surface properties with a contact angle of approximately 160 • . Owing to the cost efficiency of mass production and the fidelity of the strategy, the methodology could provide a general approach for fabricating complex three-dimensional periodic hierarchical structures onto a single chip and can be applied to various fields of multifunctional applications.

High‐Aspect‐Ratio Nanostructured Surfaces as Biological Metamaterials

“…Aside from defining the initial nanostructure pattern, photolithography can also be used to pattern larger order structures, e.g., to selectively remove nanostructures and nanostraws from unwanted regions, to form electrical interconnects with nanopillars, or to create hybrid micro‐ and nanoscale architectures …”

“…[39][40][41][42][43][44][45][46] The description "high aspect ratio" is loosely defined in the literature, but is typically applied to structures with an aspect ratio equal to or greater than 10:1. [6,[47][48][49][50] In this context, this means the majority of nanostructures we review here are less than 10 µm high, with sub-micron tips (with a few exceptions), see Figure 3. We do not consider micropatches (also referred to as microneedles) in this review, which can share similar aspect ratios, but have heights an order of magnitude larger.…”

“…Here, we examine surfaces, rather than untethered high‐aspect‐ratio nanostructures, or single‐cell probes . The description “high aspect ratio” is loosely defined in the literature, but is typically applied to structures with an aspect ratio equal to or greater than 10:1 . In this context, this means the majority of nanostructures we review here are less than 10 µm high, with sub‐micron tips (with a few exceptions), see Figure .…”

Influence of laser geometric morphology type on SiC surface wettability

“…According to the published work, the influence of circledimpled and micro-square-convex morphology on surface wettability has a hot topic of research [7][8][9]. Tseng et al [10] experimentally showed that circle-dimpled morphology can enhance the hydrophilicity of silicon surfaces, decreasing contact angles from 47.9° to 0° in a very short time.…”

Physicochemical Characteristics and Droplet Impact Dynamics of Superhydrophobic Carbon Nanotube Arrays

“…Si nanoparticles [1][2][3] Sol-gel Sol gel 165-173 3 1.4x10 5 -1.6x10 6 Si nanopillars [4][5][6] Ca ≤ 3.13x10 -2 , respectively. This condition implies the following: the effect of inertia is stronger than that of gravity, the effect of gravity is comparable to that of surface tension, and the effect viscosity is much less than that of surface tension.…”