Flexible Superhydrophobic Microlens Arrays for Humid Outdoor Environment Applications

Biomimetic Superhydrophobic Surfaces by Nanoarchitectonics with Natural Sunflower Pollen

Superhydrophobic surfaces, known for their water-repellent, and self-cleaning properties, are widely used in various applications. These advanced functional surfaces exhibit high contact angles (>150°), achieved through low surface energy chemistries and hierarchical roughness. Natural sunflower pollen is micron-sized spherical particles with nano-sized spikes on the surface. This study engineered superhydrophobic coatings using the unique hierarchical structure of sunflower pollen and low surface energy additives like polydimethylsiloxane (PDMS) and silane additives such as 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FTS), octadecyltrichlorosilane (OTS) and dichlorodimethylsilane (DCDMS). The pollen content significantly modulates surface structure, roughness, and water contact angle. Higher pollen content enhances roughness and water repellency by creating micro-nano hierarchical structures. Pollen-PDMS-FTS and Pollen-PDMS coatings demonstrated the highest water contact angles (165 ± 2° and 163 ± 3°, respectively) and lowest sliding angles (4.5 ± 1° and 7.6 ± 2.6°, respectively), achieving a "lotus effect." Conversely, Pollen-PDMS-OTS or Pollen-PDMS-DCDMS coatings resulted in high sliding angles and water adhesion, producing a "rose petal effect." These "lotus effect" coatings are effectively applied in self-cleaning and water displacement in oil pipelines on hilly terrain. This study provides insights into the interplay between hierarchical structure and surface-free energy for designing superhydrophobic surfaces tailored for specific applications.

An Improved 3D OPC Method for the Fabrication of High-Fidelity Micro Fresnel Lenses

Based on three-dimensional optical proximity correction (3D OPC), recent advancements in 3D lithography have enabled the high-fidelity customization of 3D micro-optical elements. However, the micron-to-millimeter-scale structures represented by the Fresnel lens design bring more stringent requirements for 3D OPC, which poses significant challenges to the accuracy of models and the efficiency of algorithms. Thus, a lithographic model based on optical imaging and photochemical reaction curves is developed in this paper, and a subdomain division method with a statistics principle is proposed to improve the efficiency and accuracy of 3D OPC. Both the simulation and the experimental results show the superiority of the proposed 3D OPC method in the fabrication of Fresnel lenses. The computation memory requirements of the 3D OPC are reduced to below 1%, and the profile error of the fabricated Fresnel lens is reduced 79.98%. Applying the Fresnel lenses to an imaging system, the average peak signal to noise ratio (PSNR) of the image is increased by 18.92%, and the average contrast of the image is enhanced by 36%. We believe that the proposed 3D OPC method can be extended to the fabrication of vision-correcting ophthalmological lenses.

3D OPC method for controlling the morphology of micro structures in laser direct writing

A 3D optical proximity correction (OPC) method for controlling the morphology of micro-structures in laser direct writing is proposed, considering both the optical proximity effect and nonlinear response of a thick-film photoresist. This method can improve the manufacturability and optical performance of devices, and can be used for most 3D micro\nano structures. Its application in the fabrication of a quadratic curvature microlens array shows that the shape of the lens is well controlled; that is, when the height of the lens is 5.25 µm, the average height error of the lens shape is less than 5.22%.