Purpose.: The purpose of our study is to evaluate the biocompatibility of various polymers used as microelectrode arrays (MEAs) in retinal prostheses through in vitro cytotoxicity testing following a standardized method. Methods.: Three types of polymer-based MEAs were examined: silicone-based platinum, polyimide-based gold and liquid crystal polymer (LCP)-based gold MEAs. The silicone/platinum MEAs were fabricated by a Nd:YAG laser, polyimide/gold MEAs by a semiconductor manufacturing technique, and LCP/gold MEAs by laser micromachining and thermal-bonding process. All experimental procedures followed the International Organization for Standardization (ISO) 10993-5. To obtain the extracts of specimens, 4 g of each type of MEA were eluted by culture media, MEM, for 24 hours. Then, several diluents of extracts, including the original extracts, were applied to a cultured-cell monolayer, L929 fibroblasts. The morphologic changes of cells were analyzed by microscope after 24 and 48 hours of incubation. The quantitative evaluations of cell viability were performed by MTT assay after 24 hours of incubation. Results.: The microscopic evaluations revealed that extracts from polymer-based MEAs did not induce morphologic changes or reduction of cells compared with control irrespective of concentrations of extracts. The MTT assay showed high viability values of approximately 80 to 130% regardless of diluted ratio of extracts from polymer-based MEAs. None of the polymers demonstrated a significant reduction of cell viability when compared with control. Conclusions.: All types of polymer-based MEAs, including silicone/platinum, polyimide/gold, and LCP/gold MEAs, meet the criteria of biocompatibility guided by international standards, ISO 10993-5.

The natural compound eye system has many outstanding properties, such as a more compact size, wider-angle view, better capacity to detect moving objects, and higher sensitivity to light intensity, compared to that of a single-aperture vision system. Thanks to the development of micro- and nano-fabrication techniques, many artificial compound eye imaging systems have been studied and fabricated to inherit fascinating optical features of the natural compound eye. This paper provides a review of artificial compound eye imaging systems. This review begins by introducing the principle of the natural compound eye, and then, the analysis of two types of artificial compound eye systems. We equally present the applications of the artificial compound eye imaging systems. Finally, we suggest our outlooks about the artificial compound eye imaging system.

Holographic near-eye displays are a promising technology to solve long-standing challenges in virtual and augmented reality display systems. Over the last few years, many different computer-generated holography (CGH) algorithms have been proposed that are supervised by different types of target content, such as 2.5D RGB-depth maps, 3D focal stacks, and 4D light fields. It is unclear, however, what the perceptual implications are of the choice of algorithm and target content type. In this work, we build a perceptual testbed of a full-color, high-quality holographic near-eye display. Under natural viewing conditions, we examine the effects of various CGH supervision formats and conduct user studies to assess their perceptual impacts on 3D realism. Our results indicate that CGH algorithms designed for specific viewpoints exhibit noticeable deficiencies in achieving 3D realism. In contrast, holograms incorporating parallax cues consistently outperform other formats across different viewing conditions, including the center of the eyebox. This finding is particularly interesting and suggests that the inclusion of parallax cues in CGH rendering plays a crucial role in enhancing the overall quality of the holographic experience. This work represents an initial stride towards delivering a perceptually realistic 3D experience with holographic near-eye displays.