Effects of Stimulation Conditions and Waveforms on Muscle Contractile Characteristics

Song Tongjin,Khang Gon The Korean Society of Medical and Biological Engin 2005 의공학회지 Vol.26 No.2

This study was designed to apply the stimulation system developed in our laboratory to investigate how the stimulation conditions affect the muscle contractile characteristics in the isometric condition as well as during the FES standing/walking. Four paraplegic and ten healthy subjects participated in this study, and their knee extensors were voluntary contracted or electrically stimulated to measure the muscle force and the fatigue index for different waveforms of the pulse train. We also investigated different combinations of the electrode positions during standing/walking. It was confirmed that continuous and high-frequency stimulation causes faster fatigue than intermittent and low-frequency stimulation. Fatigue resistance was higher around the optimal muscle length than at a stretched position in healthy subjects, whereas the opposite was observed in paralyzed subjects. The paired t-test results with the level of significance at 0.01 indicated that the sinusoidal waveform generated the largest torque among the four typical waveforms. Although statistically not very significant, the sinusoidal waveform also generated, in general, the highest fatigue resistance at an intensity level below the supramaximal stimulation. One of the paraplegic subject who participated in the standing/walking program can now stand up for 1 minute and 50 seconds with the knee extensors, and walk for about 5 minutes at the speed of 12m/sec.

표면 전극용 기능적 전기자극 시스템의 개발 및 하반신 마비환자의 보행

송동진,이정한,강곤,Song Tongjin,Yi Jeong Han,Khang Gon 대한의용생체공학회 2003 의공학회지 Vol.24 No.6

본 연구에서는 표면 전극을 사용하는 8채널 전기자극 시스템을 개발하였고. 이 시스템을 이용하여 하반신 마비한자의 근력강화를 위한 전기자극 엑서사이즈와 FES 보행을 하였다. 본 연구에서 개발한 전기자극 시스템은 컴퓨터 프로그램, 전기자극기, 그리고 컴퓨터 프로그램과 전기자극기를 연결하는 통신부분으로 구성되어 있다. 컴퓨터 프로그램에서는 마우스를 이용하여 임의의 자극 패턴을 손쉽게 구성하고 편집학 수 있으며 이렇게 구성/편집된 자극 패턴은 동원곡선(recruitment curve)을 통하여 자극 파라미터로 변환된다. 자극 파라미터는 직렬통신을 이용하여 전기자극기에 전달된다. 전기자극기는 주제어부에 1개, 각 채널에 1개씩 총 9개의 마이크로프로세서로 구성되어 있다. 주제어부의 마이크로프로세서가 컴퓨터 프로그램과 통신을 하고 각 채널의 마이크로프로세서를 제어한다. 본 연구에서 개발한 기능적 전기자극 시스템으로 하반신 마비환자에게 100주 동안 전기자극 엑서사이즈를 실시한 결과 근력, 다리둘레, 그리고 피로저항성의 증가를 볼 수 있었다. 전기자극 엑서사이즈로 무릎신근(knee extensor muscle)이 체중을 지지한 수 있을 정도로 증가한 후에 FES 보행을 시작하였고, 현재 2분 동안 50m 이상 보행할 수 있다. We developed a PC-based 8-channel electrical stimulation system for transcutaneous functional electrical stimulation (FES), and applied it to FES exercise and paraplegic walking. The PC program consists of four parts: a database, a stimulation pattern generator, a stimulus parameter converter, and an exercise program. The stimulation pattern can be arbitrarily generated and edited by using the mouse on the PC screen, and the resulting stimulus parameters arc extracted from the recruitment curves, and transmitted to the 8-channel stimulator through the serial port. The stimulator has nine microprocessors: one master and eight slaves, Each channel is controlled by the slave microprocessor, and is operated independently. Clinical application of the system to a paraplegic patient showed significant increase in the knee extensor torque, the fatigue resistance, and the leg circumference, The patient can now walk about 50 meters for more than 2 minutes.

Effects of the Stimulus Parameters on the Tactile Sensations Elicited by Single-Channel Transcutaneous Electrical Stimulation

Ara, Jawshan,Hwang, Sun Hee,Song, Tongjin,Khang, Gon 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.2

This study was designed to answer the following three questions: (1) is it possible to elicit tactile stimulations by applying electrical stimulation to the skin?, (2) if so, how are the sensations affected by the stimulus parameters, pulse frequency, pulse amplitude (current), pulse width, polarity, and inter-electrode distance?, and (3) what is the relationship between the nerve afferents and the tactile sensations? The rectangular monophasic pulse train was applied to the subject's fingerpad for two types of experiments; amplitude/frequency modulations. In both types of experiments, we were able to elicit 4 major tactile sensations; tickling, pressure, low-frequency vibration, and high-frequency vibration. More than 95% of the subjects reported a consistent sensation order for each modulation. The narrow pulse width required a lower stimulation intensity to elicit a tactile sensation, and provided clearer sensations than the wide pulse width. The pulse polarity did not make a significant difference in the sensation quality. The long inter-electrode distance resulted in a lower stimulation intensity to elicit a tactile sensation than the short inter-electrode distance. Our observations suggested that the PC-like unit may be responsible for tickling, and that the FA1 nerve afferents for not only the low-frequency vibration but also the high-frequency vibration.

전기자극의 강도와 측정전극의 간격이 감각신경신호의 파라미터에 미치는 영향 연구

임경민,송동진,Lim, Kyeong Min,Song, Tongjin 대한의용생체공학회 2014 의공학회지 Vol.35 No.6

This study was designed to investigate the effects of stimulation intensity and inter-electrode distance on the parameters of the measured sensory nerve signal. 30 healthy subjects participated in this study. Sensory nerve signals were elicited by four different pulse amplitudes, i.e., 3, 6, 9, 12 mA, with the pulse width fixed at $500{\mu}s$. The sensory nerve signals elicited by the four different pulse amplitudes were measured by four different inter-electrode distances (20, 30, 40, and 50 mm). We extracted four parameters (pulse amplitude, pulse width, pulse area, and latency time from stimulation) from the sensory nerve signals. The measured pulse amplitude and pulse width were increased when the measuring inter-electrode distance was increased while the stimulating pulse amplitude was fixed. The measured pulse amplitude was saturated with the stimulating pulse amplitudes of over 6 mA while measuring inter-electrode distance. Under the same condition, measured pulse width was increased, and sensory nerve signal was initiated early. Sensory nerve signals, specially those of pulse amplitude, were distorted by a differential amplification method that commonly measures the human body signal. The experimental results indicate that the differential amplification method is required to be replaced when measuring nerve signals. Our observations suggested that the hyperpolarization of the action potential of the sensory nerve signal for preventing distortion could be used to clarify the correlation between the parameters of the sensory nerve signals and quantification of sensations.

Behavior of Al/Cu/Ti electrodes in surface acoustic wave filter at high power

Qi Li,Sulei Fu,Zengtian Lu,Lirong Qian,Rui Wang,Tongjin Chen,Cheng Song,Fei Zeng,Weibiao Wang,Feng Pan 한국물리학회 2019 Current Applied Physics Vol.19 No.4

Driven by the need for high data-rates and continuous reduction in device size, surface acoustic wave filters are required to work under increasingly high power. In this work, a series of 2.7 GHz surface acoustic wave filters with Al/Cu/Ti three-layered electrode were fabricated and loaded with high power. Those three-layered electrodes showed weaker texture but higher stability than Al-Cu alloy electrode at high power. Morphologies, microstructures and elements distribution in cross section of fingers were analyzed carefully before and after high power loading. Results show that the circular-arc-shaped outline of fingers were appeared in most samples after high power loading, and the number of gains in the finger cross section changed from some into several with much larger volume. The features of distribution of Cu atoms also coincided with these microstructures. By finite element method and phase diagram analysis, the higher stability of Al/Cu/Ti three-layered electrodes are attributed to precipitation of θ-CuAl2 in the bottom edge of electrode finger and Cu-doped α-Al in the center top.

Adaptation of Sensory Nerve Afferents for Selective Elicitation of Tactile Sensations

안보영(Boyoung An),마주형(Joohyung Ma),황선희(Sun Hee Hwang),송동진(Tongjin Song),강곤(Gon Khang) Korean Society for Precision Engineering 2015 한국정밀공학회지 Vol.32 No.10

전기자극 변조방식이 체성감각에 미치는 영향

황선희(Sun Hee Hwang),아라조샨(Jawshan Ara),송동진(Tongjin Song),배태수(Tae Sue Bae),박상혁(Sang-Hyuk Park),강곤(Gon Khang) Korean Society for Precision Engineering 2012 한국정밀공학회지 Vol.29 No.7