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Jeong, Joonsoo,Hyun Bae, So,Min, Kyou Sik,Seo, Jong-Mo,Chung, Hum,June Kim, Sung IEEE 2015 IEEE Transactions on Biomedical Engineering Vol.62 No.3
<P>A novel retinal prosthetic device was developed using biocompatible liquid crystal polymer (LCP) to address the problems associated with conventional metal- and polymer-based devices: the hermetic metal package is bulky, heavy, and labor-intensive, whereas a thin, flexible, and MEMS-compatible polymer-based system is not durable enough for chronic implantation. Exploiting the advantageous properties of LCP such as a low moisture absorption rate, thermobonding, and thermoforming, we fabricate a small, light-weight, long-term reliable retinal prosthesis that can be conformally attached on the eye-surface. A LCP fabrication process using monolithic integration and conformal deformation was established enabling miniaturization and a batch manufacturing process as well as eliminating the need for feed-through technology. The functionality of the fabricated device was tested through wireless operation in saline solution. Its efficacy and implantation stability were verified through in vivo animal tests by measuring the cortical potential and monitoring implanted dummy devices for more than a year, respectively.</P>
Jeong Hoan Park,Shinyong Shim,Joonsoo Jeong,Sung June Kim 대한전자공학회 2017 Journal of semiconductor technology and science Vol.17 No.1
We propose a novel multi-photodiode array (MPDA) based retinal implant IC with on/off stimulation strategy for a visual prosthesis with improved spatial resolution. An active pixel sensor combined with a comparator enables generation of biphasic current pulses when light intensity meets a threshold condition. The threshold is tuned by changing the discharging time of the active pixel sensor for various light intensity environments. A prototype of the 30-channel retinal implant IC was fabricated with a unit pixel area of 0.021㎟, and the stimulus level up to 354 μA was measured with the threshold ranging from 400 lx to 13120 lx.
Long-term evaluation of a liquid crystal polymer (LCP)-based retinal prosthesis
Jeong, Joonsoo,Hyun Bae, So,Seo, Jong-Mo,Chung, Hum,June Kim, Sung IOP 2016 Journal of neural engineering Vol.13 No.2
<P> <I>Objective</I>. The aim of this study is to evaluate the long-term reliability of a recently presented liquid crystal polymer (LCP) -based retinal prosthesis <I>in vitro</I> as well as <I>in vivo</I>. Because an all-polymer implant introduces another intrinsic leak type due to gas permeation, for which the traditional helium leak test for metallic packages was not designed to quantify, a new method to investigate its durability is required. <I>Approach</I>. We designed and carried out a series of reliability tests specifically for all-polymer implants by quantitatively investigating moisture ingress through various pathways of the polymer surface, and the polymer–polymer and polymer–metal adhesions. Moisture permeation through the bulk material was estimated by analytic calculation, while water ingress through the adhesively sealed LCP–LCP and LCP–metal interfaces was investigated using the separate parts of an electrode array and a package in an accelerated aging condition. <I>In vivo</I> tests were done in rabbits to examine the long-term biocompatibility and implantation stability by fundus observation and optical coherence tomography (OCT) imaging. <I>Main results</I>. The analytic calculation estimated good barrier properties of the LCP. Samples of the LCP-based electrode array failed after 114 days in 87 °C saline as a result of water penetration through the LCP–metal interface. An eye-conformable LCP package survived for 87 days in an accelerated condition at 87 °C. The <I>in vivo</I> results confirmed that no adverse effects were observed around the retina 2.5 years after the implantation of the device. <I>Significance</I>. These long-term evaluation results show the potential for the chronic use of LCP-based biomedical implants to provide an alternative to traditional metallic packages.</P>
Park, Jeong Hoan,Shim, Shinyong,Jeong, Joonsoo,Kim, Sung June The Institute of Electronics and Information Engin 2017 Journal of semiconductor technology and science Vol.17 No.1
We propose a novel multi-photodiode array (MPDA) based retinal implant IC with on/off stimulation strategy for a visual prosthesis with improved spatial resolution. An active pixel sensor combined with a comparator enables generation of biphasic current pulses when light intensity meets a threshold condition. The threshold is tuned by changing the discharging time of the active pixel sensor for various light intensity environments. A prototype of the 30-channel retinal implant IC was fabricated with a unit pixel area of $0.021mm^2$, and the stimulus level up to $354{\mu}A$ was measured with the threshold ranging from 400 lx to 13120 lx.
Performance Study of Satellite Image Processing on Graphics Processors Unit Using CUDA
Jeong, In-Kyu,Hong, Min-Gee,Hahn, Kwang-Soo,Choi, Joonsoo,Kim, Choen The Korean Society of Remote Sensing 2012 大韓遠隔探査學會誌 Vol.28 No.6
High resolution satellite images are now widely used for a variety of mapping applications including photogrammetry, GIS data acquisition and visualization. As the spectral and spatial data size of satellite images increases, a greater processing power is needed to process the images. The solution of these problems is parallel systems. Parallel processing techniques have been developed for improving the performance of image processing along with the development of the computational power. However, conventional CPU-based parallel computing is often not good enough for the demand for computational speed to process the images. The GPU is a good candidate to achieve this goal. Recently GPUs are used in the field of highly complex processing including many loop operations such as mathematical transforms, ray tracing. In this study we proposed a technique for parallel processing of high resolution satellite images using GPU. We implemented a spectral radiometric processing algorithm on Landsat-7 ETM+ imagery using CUDA, a parallel computing architecture developed by NVIDIA for GPU. Also performance of the algorithm on GPU and CPU is compared.
A wireless power transmission system for implantable devices in freely moving rodents.
Eom, Kyungsik,Jeong, Joonsoo,Lee, Tae Hyung,Kim, Jinhyung,Kim, Junghoon,Lee, Sung Eun,Kim, Sung June P. Peregrinus Ltd.] 2014 Medical & biological engineering & computing Vol.52 No.8
<P>Reliable wireless power delivery for implantable devices in animals is highly desired for safe and effective experimental use. Batteries require frequent replacement; wired connections are inconvenient and unsafe, and short-distance inductive coupling requires the attachment of an exterior transmitter to the animal's body. In this article, we propose a solution by which animals with implantable devices can move freely without attachments. Power is transmitted using coils attached to the animal's cage and is received by a receiver coil implanted in the animal. For a three-dimensionally uniform delivery of power, we designed a columnar dual-transmitter coil configuration. A resonator-based inductive link was adopted for efficient long-range power delivery, and we used a novel biocompatible liquid crystal polymer substrate as the implantable receiver device. Using this wireless power delivery system, we obtain an average power transfer efficiency of 15.2% (minimum efficiency of 10% and a standard deviation of 2.6) within a cage of 152015 cm3.</P>