Development of Microelectrode Arrays for Artificial Retinal Implants using Liquid Crystal Polymers
Seung Woo Lee 1*,
Jong-Mo Seo 2,
Seungmin Ha 3,
Eui Tae Kim 1,
Hum Chung 3,
and
Sung June Kim 1
1 School of Electrical Engineering and Computer Science, Seoul National University, Seoul, Korea, Republic of; Nano Bioelectronics & Systems Research Center, Nano Artificial Vision Research Center, Seoul National University, Seoul, Korea, Republic of
2 School of Electrical Engineering and Computer Science, Seoul National University, Seoul, Korea, Republic of; Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea, Republic of; Nano Bioelectronics & Systems Research Center, Nano Artificial Vision Research Center, Seoul National University, Seoul, Korea, Republic of
3 Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea, Republic of; Nano Bioelectronics & Systems Research Center, Nano Artificial Vision Research Center, Seoul National University, Seoul, Korea, Republic of
* To whom correspondence should be addressed. E-mail: leon799{at}snu.ac.kr.
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Abstract |
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Purpose: To develop a liquid crystal polymer (LCP) based, long-term implantable, retinal stimulation microelectrode array using a novel fabrication method.
Methods: The fabrication process used laser micromachining and customized thermal-press bonding to produce LCP based microelectrode arrays. To evaluate the fabrication process and the resulting electrode arrays, in vitro reliability tests and in vivo animal experiments were performed. The in vitro tests consisted of electrode site impedance recording and electrode inter-layer adhesion monitoring during accelerated soak tests. For in vivo testing, the fabricated electrode arrays were implanted in the suprachoroidal space of rabbit eyes. Optical coherence tomography (OCT) and electrically evoked cortical potentials (EECPs) were used to determine long-term biocompatibility and functionality of the implant.
Results: The fabricated structure had a smooth, rounded edge profile and exhibited moderate flexibility, which are advantageous features for safe implantation without guide tools. Following accelerated soak tests at 75°C in phosphate buffered saline, the electrode sites showed no degradation and the inter-layer adhesion of the structure showed acceptable stability for more than 2 months. The electrode arrays were safely implanted in the suprachoroidal space of rabbit eyes, and EECP waveforms were recorded. Over a 3-month postoperative period, no choroioretinal inflammation or structural deformities were observed by OCT and histological examination.
Conclusions: LCP based flexible microelectrode arrays can be successfully applied as retinal prostheses. The results demonstrate that such electrode arrays are safe, biocompatible, mechanically stable, and can be effective as part of a chronic retinal implant system.
Key Words:
Liquid crystal polymer (LCP), optical coherence tomography, Microelectrode, Retinal prosthesis, Blister test, Electrically evoked cortical potentials
