Flexible Superhydrophobic Microlens Arrays for Humid Outdoor Environment Applications

Abstract

A microlens array (MLA) is an essential optical imaging device in the applications of augmented and virtual realities. The imaging of MLA would become blurry in a humid outdoor atmosphere. While the incorporation of superhydrophobicity to MLA would prevent the adhesion of droplets, the complex structure and the multiple fabrication process reduce the capability of optical imaging of MLA. Herein, a flexible superhydrophobic MLA with good optical imaging capability is successfully fabricated by the combination of 3D direct laser writing (DLW) and soft lithography. 3D DLW allows the fabrication of MLA with a hierarchical pillar array (h-MLA) in one step, which ensures good optical properties of the resulting polydimethylsiloxane (PDMS) h-MLA. The resulting h-MLAs with pitches ranging between 50 and 100 μm are superhydrophobic from which water droplets slide away at a sliding angle smaller than 15.6°and bounce off from the surface. Meanwhile, the hierarchical pillar array has a limited impact on the imaging capability and the field of view of h-MLA. With an optimized pitch of 60 μm, h-MLA has a transparency as good as MLA. Moreover, PDMS h-MLA retains excellent optical and superhydrophobic properties when bent and in an extremely humid environment. We believe that the proposed h-MLA could find applications in outdoor environments.

Controlling self-healing of optical field based on moiré dual-microlens arrays

“…In this work, inspired by the moiré technique, we experimentally and theoretically demonstrate the generation of self-healing optical fields by using moiré distributed dual-microlens arrays. The microlens array is a typical and crucial diffractive optical element that is widely used in various optical fields, such as fiber coupling [44], sensing [45], beam shaping [46], artificial compound eyes [47], solar cells [48], imaging technology [49,50] and even nonlinear filamentation control [51]. As a comparison, the propagation of optical field modulated by a single microlens array is also presented.…”

Concave microlens arrays with tunable curvature for enhanced photodegradation of organic pollutants in water: A non‐contact approach

“…However, the uniformity of concave MLAs is hard to control during the condensation process 39 . In another typical indirect method, soft lithography, multiple concave MLAs can be fabricated from the same mother template, and the high transparency of commonly used silane for the method makes it widely applied in optoelectronic devices 40–43 …”

“…In soft lithography, convex MLAs usually act as mother templates to prepare concave MLAs. To precisely control the shape and uniformity of convex MLAs as templates, several technologies have been developed, 19 such as hot embossing, 44,45 thermal reflowing, 46,47 inkjet printing technology, 29,48,49 and laser‐based fabrication methods 42,50 . Among all reported methods, there is one type that convex MLAs can be made by locally photopolymerizing surface microdroplets obtained from a solvent exchange process, which is highly desired to produce mother templates for concave MLAs 51,52 .…”

“…39 In another typical indirect method, soft lithography, multiple concave MLAs can be fabricated from the same mother template, and the high transparency of commonly used silane for the method makes it widely applied in optoelectronic devices. [40][41][42][43] In soft lithography, convex MLAs usually act as mother templates to prepare concave MLAs. To precisely control the shape and uniformity of convex MLAs as templates, several technologies have been developed, 19 such as hot embossing, 44,45 thermal reflowing, 46,47 inkjet printing technology, 29,48,49 and laser-based fabrication methods.…”

“…To precisely control the shape and uniformity of convex MLAs as templates, several technologies have been developed, 19 such as hot embossing, 44,45 thermal reflowing, 46,47 inkjet printing technology, 29,48,49 and laser-based fabrication methods. 42,50 Among all reported methods, there is one type that convex MLAs can be made by locally photopolymerizing surface microdroplets obtained from a solvent exchange process, which is highly desired to produce mother templates for concave MLAs. 51,52 In this solvent exchange approach, surface microdroplets containing monomers and photoinitiators form on pre-patterned substrates due to oversaturation.…”