• JSTS:Journal of Semiconductor Technology and Science
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• 제14권5호
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• pp.658-665
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• 2014

The neural stimulators have been employed to the visual prostheses system based on the functional electrical stimulation (FES). Due to the size limitation of the implantable device, the smaller area of the unit current driver pixel is highly desired for higher resolution current stimulation system. This paper presents a 16-channel compact current-mode neural stimulator IC with digital to analog converter (DAC) sharing scheme for artificial retinal prostheses. The individual pixel circuits in the stimulator IC share a single 6 bit DAC using the sample-and-hold scheme. The DAC sharing scheme enables the simultaneous stimulation on multiple active pixels with a single DAC while maintaining small size and low power. The layout size of the stimulator circuit with the DAC sharing scheme is reduced to be 51.98 %, compared to the conventional scheme. The stimulator IC is designed using standard $0.18{\mu}m$ 1P6M process. The chip size except the I/O cells is $437{\mu}m{\times}501{\mu}m$.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권1호
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• pp.79-86
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• 2013

We describe a neural stimulator front-end with arbitrary stimulation waveform generator and adaptive supply regulator (ASR) for visual prosthesis. Each pixel circuit generates arbitrary current waveform with 5 bit programmable amplitude. The ASR provides the internal supply voltage regulated to the minimum required voltage for stimulation. The prototype is implemented in $0.35{\mu}m$ CMOS with HV option and occupies $2.94mm^2$ including I/Os.

• Clinical Pain
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• 제18권1호
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• pp.36-39
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• 2019

Chronic postoperative inguinal pain (CPIP) is a major complication after inguinal herniorrhaphy. We report the treatment of CPIP using ultrasonography-combined with nerve stimulator for injection of the genitofemoral nerve (GFN). A 59-year-old man underwent laparoscopic herniorrhaphy and presented with numbness from the inguinal region to the scrotum after operation. In the pain clinic, ultrasonography-guided GFN block and pharmacological treatments had little effect. Six month after operation, patient was referred to the Department of Physical Medicine and Rehabilitation, and ultrasonography-combined with nerve stimulator for GFN injection underwent to enhance the accuracy of neural approach. The induction of scrotal contraction and paresthesia on the GFN distribution was monitored by nerve stimulator and local anesthetic was injected. After the block, pain relief lasted for 6 months without analgesic use. Ultrasonography-combined with nerve stimulator is an effective approach to treat CPIP as it enhances precise localization and injection of small peripheral nerve like GFN.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권1호
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• pp.120-128
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• 2017

This paper describes a neural stimulation system that employs an inductive coupling link to transfer power and data wirelessly. For the reliable data and power delivery, a self-referenced amplitude-shift keying (ASK) demodulator and a wide-range voltage regulator are suggested and implemented in the proposed stimulator system. The prototype fabricated in 0.35 um BCD process successfully transferred 1.2 Kbps data bi-directionally while supplying 4.5 mW power to internal MCU and stimulation block.

• 전자공학회논문지
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• 제52권5호
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• pp.58-65
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• 2015

본 논문에서는 신경 관련 인공 전자기기를 위한 신경 자극 집적회로를 $0.18-{\mu}m$ 표준 CMOS 반도체 공정을 이용하여 설계하였다. 제안 된 신경 자극 회로는 12.8-V 전원을 사용하면서 $10-k{\Omega}$의 부하에 최대 1 mA의 전류까지 전달이 가능하다. 표준 CMOS 공정 기술로 구현을 위해서 저전압 트랜지스터만을 이용하여 설계를 하였고, 고전압에서의 안정적인 동작을 위하여 트랜지스터 스태킹 기술을 적용하였다. 또한, 신경 자극 동작 후 전하 잔여량이 남아 있지 않도록 active charge balancing회로를 포함하였다. 제안 된 단일 채널 자극 집적회로의 경우 디지털-아날로그 변환기, 전류 출력 드라이버, 레벨 시프터, 디지털 제어 부분, 그리고 active charge balancing 회로까지 모두 포함하여 전체 칩 레이아웃 면적은 $0.13mm^2$을 차지하며, 다중 채널 방식의 신경 자극 기능의 체내 이식용 인공 전자기기 시스템에 적용을 하는데 적합하다.

• 전자공학회논문지SC
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• 제44권2호
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• pp.18-23
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• 2007

체내 통신은 인체를 통신 매체로 하여 신호를 전송하는 무선 통신 방식이다. 체내 통신 방식은 체내와 송수신 시스템 그리고 외부 접지를 통한 하나의 전류 패스를 형성함으로써 이루어지는데, 인공 와우와 같은 신경 보철 장치의 경우 피하에 이식되어 있기 때문에 외부 접지를 사용하기 어렵다. 따라서 본 논문에서는 이와 같은 접지의 영향을 받지 않는 체내 통신을 제안하여 신경 보철 장치를 위한 시스템을 개발하였다. 개발된 시스템은 이식된 보철 장치의 체내에 위치한 전극으로의 신호 전송이 가능하도록 설계되었다. 효과적인 통신을 위하여 실험동물의 피부 위 실험 및 피하 실험을 통해 신호 전송 특성을 조사하였으며, 피부 위 실험의 경우 약 10MHz, 피하 실험의 경우 약 3MHz 이상의 주파수 대역에서 최대 전송 이득을 가지는 것을 확인하였다. 본 시스템은 데이터 전송률 480kbps를 갖는 pulse width modulation (PWM) 방식을 사용한 인공 와우용 내부 전류 자극기에 적용하여 그 성능을 입증하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권1호
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• pp.35-41
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• 2017

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.

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.153-161
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• 2007

Stroke is the second most significant disease leading to death in Korea. The conventional therapeutic approach is mainly based on physical training, however, it usually provides the limited degree of recovery of the normal brain function. The electric stimulation therapy is a novel and candidate approach with high potential for stroke recovery. The feasibility was validated by preliminary rat experiments in which the motor function was recovered up to 80% of the normal performance level. It is thought to improve the neural plasticity of the nerve tissues around the diseased area in the stroked brain. However, there are not so much research achievements in the electric stimulation for stroke recovery as for the Parkinson's disease or Epilepsy. This study aims at the developments of a wireless variable pulse generator using ZigBee communication for future implantation into human brain. ZigBee is widely used in wireless personal area network (WPAN) and home network applications due to its low power consumption and simplicity. The developed wireless pulse generator controlled by ZigBee can generate various electric stimulations without any distortion. The electric stimulation includes monophasic and biphasic pulse with the variation of shape parameters, which can affect the level of recovery. The developed system can be used for the telerehabilitation of stroke patient by remote control of brain stimulation via ZigBee and internet. Furthermore, the ZigBee connection used in this study provides the potential neural signal transmission method for the Brain-Machine Interface (BMI).

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 마이크로/바이오 가시화기술부문 학술강연회
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• pp.51-78
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• 2002

A number of research groups worldwide are studying electronic implants that can be mounted on retinal optic nerve/visual cortex to restore vision of patients suffering from retinal degeneration. The implants consist of a neural interface made of biocompatible materials, one or more integrated circuits for stimuli generation, a camera, an image processor, and a telemetric channel. The realization of these classes of neural prosthetic devices is largely due to the explosive development of micro- and nano-electronics technologies in the late $20^{th}$ century and biotechnologies more recently. Animal experiments showed promise and some human experiments are in progress to indicate that recognition of images can be obtained and improved over time. We, at NBS-ERC of SNU, have started our own retinal implant project in 2000. We have selected polyimide as the biomaterial for an epi-retinal stimulator. In-vitro and in-vivo biocompatibility studies have been performed on the electrode arrays. We have obtained good affinity to retinal pigment epithelial cells and no harmful effect. The implant also showed very good stability and safety in rabbit eye for 12 weeks. We have also demonstrated that through proper stimulation of inner retina, meaning vision can be obtained.

• 대한전자공학회논문지TE
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• 제37권2호
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• pp.41-53
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• 2000

본 논문에서는 뉴로-퍼지 방법을 이용한 한방 맥진 및 양도락 진단 알고리즘을 제안하고 DSP보드를 중심으로 한 실시간 진단 시스템을 구현한다. 맥진은 환자의 손목에 있는 촌관척부에 부착한 맥진 Probe를 통해 맥진카드의 3 채널로 신호가 입력되도록 하여, 1차적으로 좌부맥, 좌침맥, 우부맥, 우침맥으로 나누어 촌관척 3부분을 동시에 실험하고, 2차적으로는 촌관척 중 1부분씩 개별적으로도 실험을 행할 수 있도록 한다. 실제 실험을 통하여 어느 맥진 Probe로도 맥진 신호가 세밀하게 검출됨을 확인한다. 양도락 진단에서는 전기자극기에서 발생된 펄스를 인체의 일정부위에 주입하면 12경맥의 대표측정점에 부착된 전극을 통해 응답신호를 검출해 내도록 한다. 실험은 ① 1채널씩 검출, ② 2채널(좌, 우)씩 검출, ③ 6채널(좌수, 우수, 좌족, 우족)씩 4단계로 검출, ④ 24채널 동시 검출 후, 1차적으로 퍼지진단을 행하고, 2차적으로 퍼지진단값을 신경회로망의 입력으로 이용하여 신경회로망 훈련을 행하였다. 그리고 임의의 환자에게서 측정한 검출값을 곧바로 기 훈련 된 양도락 신호의 패턴인식을 행하여 양도락 신호의 뉴로-퍼지 진단이 잘 수행됨을 확인하였다.