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S. Lee, E. Kim, J. Jang, J. Jeong, J.-M. Seo, H. Chung, S. Kim; Liquid Crystal Polymer-Based Flexible Microelectrode Arrays for Chronic Retinal Prosthesis: In vitro Reliability Tests. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3051.
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For the chronically implantable retinal stimulation system, Liquid Crystal Polymer (LCP)-based microelectrode arrays (MEAs) were proposed, and in vitro reliability was investigated.
LCP-based gold MEA samples were fabricated by previously reported methods (Lee SW, et al., IOVS 2009). The MEAs were soaked in phosphate buffered saline (PBS: pH 7.4); and accelerated soak tests were performed at 90°C. During the soak tests, the electrode sites were regularly observed by microscopic examination, and the impedance of the electrode sites was measured at 1kHz 5mV sine waveform using an impedance analyzer (IM6e; Zahner-Elektrik, Kronach, Germany). LCP-based inter-digitated electrode (IDE) samples were also fabricated, and the accelerated soak tests at 75°C were performed. During the soak tests, 5 V direct current-biased electrical current was regularly applied to each channel of the IDE samples, and the leakage currents were measured by picoammeter (Model 6485, Keithley Instruments Inc).
LCP-based MEAs and IDEs were successfully fabricated and the reliability was monitored for 7 months. During the test period, no structural deformation was observed in all of the sites, and the impedance of each site was well preserved. The leakage currents of the IDE samples were monitored for 4 weeks. During the period, the leakage current was maintained at 200~900 pA.
The LCP-based MEAs have been fabricated and tested using the in vitro accelerated soak tests, and the test showed the high stability of the LCP-based MEAs in aqueous environment. These findings imply that the LCP-based MEAs might be safely used for chronic retinal prosthesis.
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