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DB Shire, JF Rizzo, J Loewenstein; Micromachined Tacks to Attach a Prosthesis to the Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4482.
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Purpose: To develop a safe and reliable means of affixing an ultrathin, flexible array of stimulating electrodes to the retina for use as a component in a retinal prosthesis. The intention of our design is to anchor the device in the sclera in a manner better suited to chronic implantation than larger, previously developed titanium tacks. Methods: A Bosch process reactive ion etcher was used to micromachine silicon retinal tacks which varied in barb design, shaft length and cross section, and head shape. Silicon-on-insulator wafers were used as the starting material, and PECVD-deposited silicon dioxide served as the etch mask. In vitro experiments were performed on human sclera tissue in which these tacks were manually inserted and removed to evaluate the efficacy of each design. Results: Our tacks (see SEM micrograph below) were able to penetrate the sclera relatively easily, and they resisted removal due to their barb structure. The tack in the photo has a shaft cross section of 100 µm2, and these devices proved to be relatively fragile. We are currently improving sturdiness and ease of insertion by means of thicker and sharper designs. A custom insertion tool made from vitreous forceps is also being developed to avoid breakage, and tack fabrication using other biocompatible materials is being investigated. Conclusions: Micromachining technology has enabled us to create a tack with appropriate geometry for affixing ultrathin membranes to the retinal surface. Similar devices for other applications are also made possible using the micro-electromechanical system (MEMS) technology employed here. View OriginalDownload SlideView OriginalDownload Slide
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