Integration of Great Water Repellence and Imaging Performance on a Superhydrophobic PDMS Microlens Array by Femtosecond Laser Microfabrication

Abstract

Microlens arrays (MLAs), as the important optical devices, are easily polluted by the water droplets or power-like-contaminates in the air. Endowing the artificial MLAs with anti-water and self-cleaning abilities remains great challenge. In this paper, the authors report a novel method for fabricating superhydrophobic polydimethylsiloxane (PDMS) MLAs by the combination of femtosecond laser wet etching and femtosecond laser direct writing methods. The resultant surface is composed of a convex MLA and the surrounding rough micro/nanoscale hierarchical structures. Water droplet on the surface of the as-prepared MLA shows a contact angle of 162 and can easily roll away when the substrate is slightly tilted 0.5 . In addition to their excellent imaging performance, such ultralow adhesive and ultrahigh superhydrophobicity also endows the as-prepared MLA with excellent anti-water ability as well as the self-cleaning function relative to the normal MLA. The authors believe that the anti-water and self-cleaning MLAs will potentially have many important applications in solar cells, medical endoscopes, and other optical systems that are often used in the humid environment or outdoors.

Mini-Review on Bioinspired Superwetting Microlens Array and Compound Eye

“…The superhydrophobic MLA still has excellent imaging performance because the surface of the microlenses is not treated by laser and remains smooth. As shown in Figure 2E , when a jet of water (blue color) is randomly sprayed onto the superhydrophobic MLA, no water residual leaves on the superhydrophobic MLA, whereas water can stick on the surface of the normal MLA, demonstrating that the as-prepared superhydrophobic MLA has remarkable water repellence (Li M. et al, 2019a ). The imaging ability of the superhydrophobic MLA is not affected by the water droplets because water is unable to adhere to the MLA.…”

“…Once the MLA surface is polluted, the contaminants will be easily removed by water droplets. During the spherical water droplets rolling off on the MLA sample, the droplets concurrently take away the dust and contaminants on their path ( Figure 2F ; Li M. et al, 2019a ).…”

“…Superwetting microstructure can be created on the flat area between microlenses rather than the top surface of the microlenses, making the whole MLA surface finally present superwettability. Li M. et al ( 2019a ) reported a superhydrophobic MLA pattern consisted of a convex MLA and the surrounding superhydrophobic microstructures on a polydimethylsiloxane (PDMS) substrate. An MLA was firstly obtained by the femtosecond laser wet etching technology and the template replicated method.…”

“…Formation of underwater superoleophobic micro/nanostructure on the top surface of the microlenses of an MLA: (M) SEM image of the underwater superoleophobic MLA, (N) 3D profile of the MLA, (O) oil droplet on the MLA surface in water, and (P) self-cleaning ability of the underwater superoleophobic MLA as the oil-polluted MLA is dipped into the water. Reproduced from Li M. et al ( 2019a ) with the permission of the WILEY-VCH. Reproduced from Bian et al ( 2020 ) with the permission of Bian et al Reproduced from Raut et al ( 2015 ) and Li J. et al ( 2019 ) with the permission of the American Chemical Society.…”

IR Artificial Compound Eye

“…The arthropod species have developed and optimized their super sophisticated compound eye vision system over millions of years of evolution, and they provide valuable sources of inspiration to human beings to track and imitate . Although the artificial compound eye (ACE) components in the visible light region are widely reported and some mimicking bio‐vision systems are demonstrated, the minimized high‐performance ACE components fully working in the IR region are still rarely reported.…”