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Das, Partha Sarati,Yoon, Hyo Sang,Kim, Jiyoung,Kim, Dae Heum,Park, Jae Yeong Elsevier 2018 MICROELECTRONIC ENGINEERING Vol.197 No.-
<P><B>Abstract</B></P> <P>Fast advancement of dry biopotential electrode has driven to the reduction of using Ag/AgCl (wet electrode). There is a necessity for development of flexible and eco-friendly micro-structured (MSE) dry biopotential electrode utilizing biodegradable and non-toxic materials for a better life and sustainable future. It is very difficult to create micro-structure without using any solvents or high-end equipment. Here, a novel micro-structured electrode coated with Ti/Au film is fabricated using a sandpaper template and is proposed for biopotential signal monitoring applications. We used sandpaper, which is recyclable and biodegradable. The proposed MSE is a flexible, stretchable, and biocompatible dry micro-structured electrode. The sheet resistance of the proposed MSE is 2.5 Ω/sq. The area of MSE was only 4 cm × 4 cm (l × w), and the sweat of the epidermis layer of human skin could be utilized as the electrolyte for the flexible MSE during the electrocardiography (ECG) and electromyography (EMG) recording. The fabricated MSE was enough thin and flexible to be well attached onto the skin. The contact impedance of the flexible MSE was stable and suitable for long-term biopotential recording. The main advantage of the electrodes is simple fabrication, which can be used in wearable electrode systems to monitor human health. The results of the experiment show that the proposed electrode can operate in dry conditions when the subject is resting, and it shows fewer motion artifacts during movement.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A sandpaper inspired micro-structure based dry electrode was newly developed for ECG and EMG signal measurement. </LI> <LI> Proposed and developed fabrication method to the sandpaper inspired electrode is simple and cost effective. </LI> <LI> The surface resistivity of the sandpaper inspired electrode was found 2.5 Ω/square. </LI> <LI> The impedance of the sandpaper inspired electrode is lower than the conventional Ag/AgCl electrode. </LI> </UL> </P>
Partha Sarati Das,Kyeong-Hwa Kim 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.11
New voltage-based on-line fault detection and faulty switch identification algorithms under multiple open-switches in a grid-connected wind power converter are proposed in this paper. The proposed algorithms are based on the three-phase voltages which are calculated by using the DC link voltage and switching times determined from the space vector PWM scheme. From the calculated three-phase voltages, the absolute of average phase voltage and normalized three-phase RMS voltages are obtained to be used for the fault detection and faulty switch identification algorithms in three-phase AC/DC PWM converter. To determine faulty switches, three-phase voltages and RMS currents are taken as faulty switch localization variables. The complete diagnosis is carried out by a simple method during operation, which does not require any additional sensors. Therefore, the proposed methods are cost-effective and easy to use. To verify the validity and performance of the proposed algorithms, the simulation is carried out using the PSIM software for twenty-one cases of faults including multiple open-switches. As a result, the proposed scheme can effectively detect the occurrence of fault as well as faulty switches for these conditions independent of operating conditions.
A sandpaper-inspired flexible and stretchable resistive sensor for pressure and strain measurement
Chhetry, Ashok,Das, Partha Sarati,Yoon, Hyosang,Park, Jae Yeong Elsevier 2018 Organic Electronics Vol.62 No.-
<P><B>Abstract</B></P> <P>We report very small shape-factored microstructures developed via a simple and cost-effective approach, enabling a high degree of sensitivity in a low-pressure regime (<2.67 kPa). The surface intertexture on the counter electrode and irregular microstructures with a high surface area developed on the base electrode help reduce the shape factor, allowing the device to deform more easily under pressure. Moreover, the irregular patterns with higher unloaded surface area strengthen the tunneling current sufficiently at low pressure. Furthermore, the fabricated features enable the device to perform as a flexible and stretchable sensing mechanism; the outstanding performance was achieved through a novel and feasible fabrication from a low-surface-energy template without surfactant coating. An ultra-low hysteresis of 3.17%, a high sensitivity of 0.3954 kPa<SUP>−1</SUP>, a fast response time of 0.49 s and stability over 6000 cycles were achieved. Finally, the sensing capability was examined by gentle finger tapping and arbitrary movement of the sensor placed on the forefinger. The current platform can be a key component for diverse applications such as muscle movement, speech detection, and health monitoring systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Flexible and stretchable resistive sensor for pressure and strain sensing capability. </LI> <LI> Very small shape-factored microstructures were generated from sandpaper template. </LI> <LI> An ultra-low hysteresis of 3.17%, a high sensitivity of 0.3954 kPa<SUP>−1</SUP> and stability over 6000 cycles were achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
A Flexible Capacitive Pressure Sensor for Wearable Respiration Monitoring System
Park, Seong Won,Das, Partha Sarati,Chhetry, Ashok,Park, Jae Yeong IEEE 2017 IEEE Sensors Journal Vol. No.
<P>This paper presents the design, fabrication, and characterization of a wearable capacitive pressure sensor for respiration-monitoring systems. For the dielectric layer of the proposed capacitive sensor, Porous Ecoflex with a porosity of similar to 36% was prepared from a manually made sugar cube via a simple melting process. A polydimethylsiloxane-based silver nanowire and carbon fibers thin films were used for the sensor electrodes. The fabricated flexible pressure sensor exhibited a high sensitivity of 0.161 kPa(-1) for low pressure regime (<10 kPa), a wide working pressure range of <200 kPa, and a high durability over 6000 cycles. Since the proposed sensor is flexible and resizable, it can be integrated into clothes and easily placed at any location of the human body. Finally, the practicality of the sensor was successfully demonstrated by integrating the sensor into a waist belt to monitor the real-time respiration signal of the human being. The finding is highly useful to monitor respiration signal for the detection of diseases, such as sleep apnea, asthma, and others.</P>