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Joonsoo Jeong, Kyou sik Min, Soowon Shin, So Hyun Bae, Jong-Mo Seo, Hum Chung, Sung June Kim; Recent Progress in Fabrication Process and the Performance of the Liquid Crystal Polymer-based Retinal Prosthesis. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1828.
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© ARVO (1962-2015); The Authors (2016-present)
A miniaturized, eye-conformable and long-term reliable retinal prosthesis using a new material of liquid crystal polymer (LCP) is being developed to overcome the problem associated with conventional metal- and polymer-based devices: hermetic metal package is bulky, heavy and labor-intensive, while thin, flexible and MEMS-compatible polymer-based system is not durable enough for chronic implantation. In the previous presentations (J. Jeong; ARVO 2012, 2013), we reported the concepts and interim results from the LCP-monolithic fabrication techniques to achieve eye-conformable and miniaturized structure. In this study, we present the recent progress in the fabrication processes to improve long-term reliability, and the performance of the finalized device.
The fabrication processes were optimized to improve the long-term reliability by means of strengthening interlayer adhesion during multilayer lamination and electronics packaging. For example, multilayered substrate was reconfigured for thicker interlayer insulation and the subsequent deformation process was sophisticated for the thicker substrate, all of which contribute to allow higher laminating force leading to stronger interlayer adhesion. Laser-thinning technique was developed for higher flexibility of LCP-based retinal electrode array. The functionality and long-term reliability of the device was assessed by wireless operation in the accelerated soaking condition.
The finalized fabrication process was established accommodating the new processes tailored for long-term reliability. The completed all-LCP retinal prosthesis has a circular package of 15 mm in diameter, and 1.3 mm in the maximum thickness of its crescent-shaped cross-section being conformal to the eye surface. The device weighs only 0.38g with 0.22cc in volume. The averaged electrochemical impedance of 16-channel electrode array is 3.67 KΩ at 1KHz, and the device could be wirelessly operated up to 15 mm from the external coil and controller. The flexibility of laser-thinned LCP retinal electrode increased two-fold compared to previous one as measured by bending test.
The slim, light-weight and eye-conformable retinal prosthesis was successfully fabricated using LCP. Accelerated soak test and in vivo animal test to verify reliability and stability of active devices for an extended period of time are ongoing at this moment.
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