This review focuses on recent developments in additive manufacturing (AM) of precision optical devices, particularly devices consisting of components with critical features at the micro-and nanoscale. These include, but are not limited to, microlenses, diffractive optical elements, and photonic devices. However, optical devices with large-size lenses and mirrors are not specifically included as this technology has not demonstrated feasibilities in that category. The review is roughly divided into two slightly separated topics, the first on meso-and microoptics and the second on optics with nanoscale features. Although AM of precision optics is still in its infancy with many unanswered questions, the references cited on this exciting topic demonstrate an enabling technology with almost unlimited possibilities. There are many high quality reviews of AM processes of non-optical components, hence they are not the focus of this review. The main purpose of this review is to start a conversion on optical fabrication based on information about 3D AM methods that has been made available to date, with an ultimate long-term goal of establishing new optical manufacturing methods that are low cost and highly precise with extreme flexibility.

In this study, a new cost-effective and high-precision process chain for the fabrication of large-scale diffractive lens arrays on chalcogenide glass is proposed. First, a positive diffractive lens array is fabricated on a PMMA master substrate by employing a step-and-repeat hot imprinting process. The direct hot imprinting can transfer the microstructures from a heated mold to the polymer substrate accurately. Repeating the hot imprinting process according to a predetermined path, the desired diffractive lens array is obtained. Unlike photolithography and electron-beam writing, which are expensive technologies with sophisticated process, the hot imprinting is an easier, cheaper and more eco-friendly method for fabricating diffractive features with continuous pro le. Afterwards a casting process is applied to create a PDMS mold with the negative features. The diffractive lens array with continuous pro le is successfully transferred from the master substrate to the PDMS elastomer, which is used as a mold for subsequent precision glass molding. Finally, the microstructures of PDMS mold are replicated to the chalcogenide glass by non-isothermal glass molding. In this process, the mold and workpiece are set at different temperatures. The PDMS mold at low temperature maintains enough rigidity, so as to press the features into the softened chalcogenide glass more easily, which is at relatively higher temperature, resulting in a positive high-delity diffractive lens array on the chalcogenide glass. Surface pro les and optical performance of the fabricated components are characterized quantitatively. Results showed that large-scale diffractive lens array with continuous pro le can be successfully fabricated on Chalcogenide glass by this proposed process chain with high quality and integrity.

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Investigations using animal model systems have been enlightening us with the biology underpinning the development of bladder cancer besides strengthening the existing therapy to improve the clinical outcome in patients. To date, spontaneous and chemical inductions are the classical methods in the generation of animal models of bladder cancer. Attributed to many benefits such as simple protocols and lower maintenance cost, these animal models are widely applied in the investigations of bladder cancer pathogenesis and screening of therapeutic drug. In this review, we give an overview of spontaneous- and chemically-induced bladder cancer animal models accompanying by the pros and cons of these two types of models. Furthermore, various chemical carcinogens used in the induction are discussed with the potential benefits and pitfalls in the establishment of animal models. This review will provide insightful information about the selection of the correct method in establishing the animal models of bladder cancer which are instrumental for studying potential therapeutic agents that target bladder cancer.