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Hydrophobic and Super-Hydrophobic Polymer Coatings
Published in Asit Baran Samui, Smart Polymers, 2022
Kirti Thakur, Swaroop Gharde, Sarang Jamdade, Balasubramanian Kandasubramanian
One of the most explicit examples was presented by Gao et al. (Gao et al. 2007) by creating a super-hydrophobic anti-fog coating for materials. This was done by mimicking mosquito compound eyes, inspired by Lee et al., who proposed a 3D optical method to synthesize artificial compound eyes, made up of microscale ommatidia placed on a hemisphere-shaped dome-like structure made of polymers (Lee and Szema 2005; Jeong, Kim and Lee 2006). The synthesis included several stages of patterning by soft lithography. First, the glass surface was covered with a photoresist coating to obtain a pattern that had the dimensions of the eyes of the mosquito, i.e., 20 µm with a 5 µm spacing. This was then heated to 120°C to obtain dome-like hemispheres made of the photoresist. The next step involved transferring this pattern onto PDMS (poly-dimethyl siloxane) which acted as a mould to replicate the photoresist structure which was also constructed by PDMS. This final PDMS structure was then pressed onto the substrate with SiO2 nanospheres at a temperature of 100°C for 3 hours and the nanospheres were transferred on the PDMS which was peeled off after cooling. The hemispheres had a 22 µm diameter and an HCP (hexagonal closed packing) structure. The static WCA and tilted angle were 155° and 15° and showed an excellent super-hydrophobic nature and also anti-fogging properties.
Introduction to Nanotechnology
Published in Wesley C. Sanders, Basic Principles of Nanotechnology, 2018
The Attacus atlas moth uses a complex imaging system with compound lenses used to accommodate low brain processing capabilities. The compound lens system contains hexagonally shaped ommatidia, each containing its own optical microlens. Similar structures are found in the compound eyes of houseflies (Figure 1.6). This allows the production of individual images, which provide insects with a large field of view without the need of increased eye volume. Interestingly, each ommatidium possesses unique nanometer-scale surface structures behaving as antireflective surfaces. This enables insect eyes to have photosensitivity in dim environments in addition to reducing reflections otherwise visible to predators (Ko et al. 2011).
In‐plane structure of single‐layer tissues
Published in A. Šiber, P. Ziherl, Cellular Patterns, 2018
The DAH criterion [Eq. (3.46)] succinctly describes the main mechanism of cell sorting and it helps us to understand the structure of the Drosophila retina as one of the paradigmatic examples of patterning in developmental biology. Like in other arthropods, the compound eye of Drosophila consists of clusters of cells called ommatidia. These clusters form a hexagonal lattice like the hair cells of the basilar papilla in Figure 3.32 but their structure is more elaborated: each cluster consists of a few (typically four) photoreceptor cone cells in the center as well as of several types of pigment cells and bristle cells arranged around the cone cells (Figure 3.34a).
A rapid precision fabrication method for artificial compound eyes
Published in International Journal of Optomechatronics, 2021
Yueqi Zhai, Jiaqi Niu, Jingquan Liu, Bin Yang
Curved microlens arrays inspired by the compound eyes of insects in nature are extensively applied in three-dimensional imaging, pinhole cameras, as well as unmanned aerial navigation, and medical endoscope.[1–6] Compared with the previous planar lens arrays, curved compound eyes are attracting more and more attention due to their advantages, such as a larger field of view (FOV) and higher sensitivity for fast-tracking and detection of moving targets.[7–10] In general, microlens arrays are made up of thousands of micron-sized lenses, known as ommatidia in insect compound eyes, that have minimal surface roughness, good homogeneity, and are sensitive to external optical information, imposing significant demands on processing accuracy.[11–14]