Mini-Review on Bioinspired Superwetting Microlens Array and Compound Eye

Abstract

Microlens arrays (MLAs) and MLA-based artificial compound eyes (ACEs) are the important miniaturized optical components in modern micro-optical systems. However, their optical performance will seriously decline once they are wetted by water droplets (such as fog, dew, and rain droplets) or are polluted by contaminations in a humid environment. In this mini-review, we summarize the research works related to the fabrication of superwetting MLAs and ACEs and show how to integrate superhydrophobic and superoleophobic microstructures with an MLA. The fabrication strategy can be split into two categories. One is the hybrid pattern composed of the MLA domain and the superwetting domain. Another is the direct formation of superwetting nanostructures on the surface of the microlenses. The superhydrophobicity or superoleophobicity endows the MLAs and ACEs with liquid repellence and self-cleaning function besides excellent optical performance. We believe that the superwetting MLAs and ACEs will have significant applications in various optical systems that are often used in the humid or liquid environment.

Superwettability‐based separation: From oil/water separation to polymer/water separation and bubble/water separation

“…Usually, an extreme wetting state can be obtained by combining proper rough microstructure and chemistry. [ 30–34 ] For example, underwater superoleophobicity, [ 35–37 ] superpolymphobicity, [ 23–25 ] and superaerophobicity [ 26–29 ] can be achieved on a hydrophilic substrate by the formation of micro/nanoscale surface structures. The underwater superoleophobic microstructures greatly repel oils, the underwater superpolymphobic microstructures repel liquid polymers, and the underwater superaerophobic microstructures repel bubbles in a water medium.…”

“…Usually, the rough surface microstructure can enhance the natural wettability of a solid material. [ 23–37 ] After the formation of conical‐shaped spikes and nanoripples structure on the mesh surface by femtosecond laser treatment, the hydrophilicity of stainless steel is greatly amplified, because laser‐induced rough microstructures can greatly increase the real surface area of the mesh substrate. [ 35 ] That is, rough microstructure makes hydrophilic substrate become more hydrophilic.…”

Underwater superpolymphobicity: Concept, achievement, and applications

“…Wettability is a basic chemical and physical property of material surfaces, which is mainly dependent on the surface chemical composition and morphology of materials. [ 37–42 ] Generally, the contact angle (CA) can characterize the static aspect of the surface wettability of a solid material. CA (“ θ ” in Figure 1A) is the angle between the horizontal line of the substrate (the solid‐liquid interface) and the tangent line at the contact point.…”

“…Various superwettabilities such as superhydrophobicity, superoleophobicity, and underwater superaerophobicity have been achieved on different solid substrates by combining proper surface microstructures and chemical composition. [ 37–48 ] Regarding these superwettabilities, water, oils, and bubbles are the main research subjects. On the other hand, polymers are the most common materials in our daily lives, which are widely used in the manufacturing industry, chemical industry, packaging, building, food processing, pharmaceutical industry, bioengineering, and so on.…”

Hierarchical Artificial Compound Eyes with Wide Field-of-View and Antireflection Properties Prepared by Nanotip-Focused Electrohydrodynamic Jet Printing

“…The moth eyes with the characteristics of wide FOV and antireflection and superhydrophobic properties are a good bionic target for the development of an optical imaging system. Inspired by moth eyes, scientists have fabricated a variety of artificial compound eyes (ACEs) with macro/micro/nano hierarchy which have diverse potential applications in areas such as optical sensors, wide-angle communication antenna, medical endoscopy imaging, and solar cells. ,− Consequently, the design and fabrication of ACEs has become an active research topic. In recent years, ACEs with hierarchical structures have been fabricated using various methods including micro/nanosphere self-assembly processing technology, − soft lithography, laser direct writing, and nanoimprint lithography .…”