• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.4
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• pp.107-113
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• 2022

At present, it is possible to manufacture electrodes down to several micrometers (~ ㎛) using inkjet printing technology owing to the development of precision ejection heads. Inkjet printing technology is also used in the manufacturing of bio-sensors, electronic sensors, and flexible displays. To reduce the difference between the electrode design/simulation performance and actual printing pattern performance, it is necessary to analyze and optimize the processable area of the ink material, which is a fluid. In this study, process optimization was conducted to manufacture an IDE pattern and fabricate an impedance sensor. A total of 25 IDE patterns were produced, with five for each lamination process. Electrode line width and height changes were measured by stacking the designed IDE pattern with a nanoparticle-based conductive ink multilayer. Furthermore, the optimal process area for securing a performance close to the design result was analyzed through impedance and capacitance. It was observed that the increase in the height of stack layer 4 was the lowest at 4.106%, and the increase in capacitance was measured to be the highest at 44.08%. The proposed stacking process pattern, which is optimized in terms of uniformity, reproducibility, and performance, can be efficiently applied to bio-applications such as biomaterial sensing with an impedance sensor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1087-1091
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• 2007

Exact impedance modeling of the electrode/electrolyte interface is important in bio-signal sensing electrode development. Therefore, the investigation of the equivalent circuit models for the interface has been pursued for a long time by several researchers. Previous circuit models fit the experimental results in limited conditions such as frequency range, type of electrode, or electrolyte. This paper describes a new electrical circuit model and its capability of fitting the experimental results. The proposed model consists of three resistors and two constant phase elements. Electrochemical impedance spectroscopy was used to characterize the interface for Au, Pt, and stainless steel electrode in 0.9% NaCl solution. Both the proposed model and the previous model were applied to fit the measured impedance results for comparison. The proposed model fits the experimental data more accurately than other models especially at the low frequency range, and it enables us to predict the impedance at very low frequency range, including DC, using the proposed model.

• Journal of Biosystems Engineering
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• v.33 no.4
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• pp.269-275
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• 2008

This study was conducted to design an impedance sensor that can measure soil water content of soils. Partial least square regression (PLSR) was applied to soil impedance data preprocessed with a smoothing method. An optimal sub-spectrum size and wavelength range were determined by comparing the coefficient of determination ($R^2$) and root mean square error (RMSE) of the PLSR models obtained using soil impedance data. various PLS analysis. Based on the PLSR analysis, it would be concluded that the optimal spectrum measurement range was $32.0{\sim}50.0\;MHz$ with the optimal sub-spectrum size of about 18.5 MHz.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.4
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• pp.9-16
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• 2014

Electrode contact resistance is a crucial factor in physiological measurements and can be an accuracy limiting factor to perform electrical impedance measurements. The electrical bio-impedance values can be calculated by the conductivity and permittivity of underlying tissue using implant electrode in human skin. In this study we focus on detecting physiological changes in the human skin layers such as the sebum layer, stratum corneum layer, epidermis layer, dermis layer, subcutaneous fat and muscle. The aim of this paper is to obtain optimal design for implantable electrode at subcutaneous fat layer through the simulation by finite element methods(FEM). This is achieved by evaluating FEM simulations geometrically for different electrodes in length(50 mm, 70 mm), in shape(rectangle, round square, sexangle column), in material(gold) and in depth(22.325 mm) based on the information coming from the subcutaneous fat layer. In bio-impedance measurement experiments, according to electrode shapes and applied voltage, we have ascertained that there was the highest difference of bio-impedance in subcutaneous fat layer. The methodology of simulation can be extended to account for different electrode designs as well as more physical phenomena that are relevant to electrical impedance measurements of skin and their interpretation.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.752-753
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• 2005

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.1926-1938
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• 2009

In this study, detection system of the blood flow variation rate was implemented using the variation effect of bio electric impedance at time of the blood pressure measurement by means of impedance method. The blood pressure measurement was performed by the oscillometric method. The mean arterial pressure was calculated using maximum amplitude algorithm. The systolic and diastolic pressure were estimated by establishment of the various characteristic ratio according to mean arterial pressure range. Alternative static current source and lock_in amplifier were introduced to impedance measurement. The variation of blood volume was measured using variation bio impedance according to induced cuff pressure at measuring area.

• Journal of Sensor Science and Technology
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• v.26 no.5
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• pp.342-347
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• 2017

We present a precision instrument amplifier (IA) designed for bio-potential acquisition. The proposed IA employs a capacitively coupled instrument amplifier (CCIA) structure to achieve a rail-to-rail input common-mode range and low gain error. A positive feedback loop is applied to boost the input impedance. Also, DC servo loop (DSL) with pseudo resistors is adopted to suppress electrode offset for bio-potential sensing. The proposed amplifier was designed in a $0.18{\mu}m$ CMOS technology with 1.8V supply voltage. Simulation results show the integrated noise of $1.276{\mu}Vrms$ in a frequency range from 0.01 Hz to 1 KHz, 65dB SNR, 118dB CMRR, and $58M{\Omega}$ input impedance respectively. The total current of IA is $38{\mu}A$. It occupies $740{\mu}m$ by $1300{\mu}m$ including the passive on-chip low pass filter.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.9
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• pp.713-719
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• 2003

This paper introduces attempts to obtain the ‘representative’ characteristics of the mechanical impedance of seated Korean subjects under vertical vibration. Individual responses of driving-point mechanical impedance obtained from forty one Korean subjects are illustrated. Four kinds of vibration levels and three different sitting postures are selected to collect the responses of each subject. Those individual responses are used to estimate the ‘mean’ mechanical impedance, which may be expected to be a representative model to Korean subjects. Several interesting features of the estimated mechanical impedance are suggested and compared to those of ISO/DIS 5982.

• Journal of Sensor Science and Technology
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• v.24 no.1
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• pp.22-28
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• 2015

This study demonstrates a polyimide nerve cuff electrode with a conductive polymer for improving recording signal quality at peripheral nerve. The nerve cuff electrodes with platinum (Pt), iridium oxide (IrOx), and poly(3,4-ethylenedioxythiophene): p-toluene sulfonate (PEDOT:pTS) were fabricated and investigated their electrical characteristics for improving recorded nerve signal quality. The fabricated nerve cuff electrodes with Pt, IrOx, and PEDOT:pTS were characterized their impedance and CDC by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The impedance of PEDOT:pTS measured at 1 kHz was $257{\Omega}$, which was extremely lower than the value of the nerve cuff electrodes with IrOx ($15897{\Omega}$) and Pt ($952{\Omega}$), respectively. Furthermore, the charge delivery capacity (CDC) of the nerve cuff electrode with PEDOT:pTS was dramatically increased to 62 times than the nerve cuff electrode with IrOx. In ex-vivo test using extracted sciatic nerve of spaque-dawley rat (SD rat), the PEDOT:pTS group exhibited higher signal-to-interference ratio than IrOx group. These results indicated that the nerve cuff electrode with PEDOT:pTS is promising for effective implantable nerve signal recording.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.399-402
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• 2002

In this study, we constructed a four-channel impedance measurement system including a two-channel goniometer to analyze human arm movement. Impedances and joint angles were simultaneously measured for wrist and elbow movements. As the impedance changes resulting from wrist and elbow movements depended heavily on electrode placement, we determined the optimal electrode configurations for those movements by searching for high correlation coefficients, large impedance changes, and minimum interferences in ten subjects (age: 29+6). Our optimal electrode configurations showed very strong relationships between the wrist joint angle and forearm impedance (correlation coefficient = 0.95+0.04), and between the elbow joint angle and upper arm impedance (correlation coefficient = -0.98+0.02). Although the measured impedances changes of the wrist (1.1+1.5 ohm) and elbow (-5.0+2.9 ohm) varied among individuals, the reproducibilities of wrist and elbow impedance changes of five subjects were 5.8+1.8 % and 4.6+1.4 % for the optimal electrode pairs, respectively. We propose that this optimal electrode configuration would be useful for future studies involving the measurement of accurate arm movements by impedance method.