• Journal of Sensor Science and Technology
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• v.29 no.5
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• pp.279-282
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• 2020

In this study, body pressure was quantitatively detected using built-in optical sensors, inside an air cushion seat. The proposed system visualizes the effect of the body pressure distribution on the air cushion seat. The built-in sensor is based on the time-of-flight (ToF) optical method, instead of the conventional electrical sensor. A ToF optical sensors is attached to the bottom surface of the air-filled cells in the air cushion. Therefore, ToF sensors are durable, as they do not come in physical contact with the body even after repeated use. A ToF sensor indirectly expresses the body pressure by measuring the change in the height of the air-filled cell, after being subjected to the weight of the body. An array of such sensors can measure the body pressure distribution when the user sits on the air cushion seat. We implemented a prototype of the air cushion seat equipped with 7 ToF optical sensors and investigated its characteristics. In this experiment, the ToF optical pressure sensor successfully identified the pressure distribution corresponding to a sitting position. The data were accessed through a mobile device.

• Journal of Sensor Science and Technology
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• v.26 no.2
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• pp.141-147
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• 2017

A pressure sensor in pulse measurement system is a core component for precisely measuring the pulse waveform of radial artery. A pulse sensor signal that measures the pulse wave in contact with the skin is affected by the temperature difference between the ambient temperature and skin surface. In this study, we found experimentally that the signal changes of the pressure sensors and a temperature sensor were caused by the temperature of the wrist surface while the pressure sensor was contacted on the skin surface for measuring pulse wave. To observe the signal change of the pulse sensor caused by temperature increase on sensor surface, Peltier device that can be kept at a set temperature was used. As the temperature of Peltier device was kept at $35^{\circ}C$ (the maximum wrist temperature), the device was put on the pulse sensor surface. The temperature and pressure signals were obtained simultaneously from a temperature sensor and six pressure sensors embedded in the pulse sensor. As a result of signal analysis, the sensor pressure was decreased during temperature increase of pulse sensor surface. In addition, the signal difference ratio of pressure and temperature sensors with respect to thickness of cover layer in pulse sensor was increased exponentially. Therefore, the signal of pressure sensor was modified by the compensation equation derived by the temperature sensor signal. We suggested that the thickness of cover layer in pulse sensor should be designed considering the skin surface temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.5
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• pp.284-288
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• 2016

Among the various physiological information that could be obtained from human body, heartbeat rate is a commonly used vital sign in the clinical milieu. Photoplethysography (PPG) sensor is incorporated into many wearable healthcare devices because of its advantages such as simplicity of hardware structure and low-cost. However, healthcare device employing PPG sensor has been issued in susceptibility of light and motion artifact. In this paper, to develop the real-time heart rate measurement device that is less sensitive to the external noises, we have fabricated an ultra-small wireless LC resonant pressure sensor by MEMS process. After performance evaluation in linearity and repeatability of the MEMS pressure sensor, heartbeat waveform and rate on radial artery were obtained by using resonant frequency-pressure conversion method. The measured data using the proposed heartbeat rate measurement system was validated by comparing it with the data of an commercialized heart rate measurement device. Result of the proposed device was agreed well to that of the commercialized device. The obtained real time heartbeat wave and rate were displayed on personal mobile system by bluetooth communication.

• International journal of advanced smart convergence
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• v.8 no.2
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• pp.227-236
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• 2019

In this study, we develop a Korotkoff sound based automatic blood pressure measurement device including sensor, hardware, and analysis algorithm. PVDF-based sensor pattern was developed to function as a vibration sensor to detect of Korotkoff sounds, and the film's output was connected to an impedance-matching circuit. An algorithm for determining starting and ending points of the Korotkoff sounds was established, and clinical data from subjects were acquired and analyzed to find the relationship between the values obtained by the auscultatory method and from the developed device. The results from 86 out of 90 systolic measurements and 84 out of 90 diastolic measurements indicate that the developed device pass the validation criteria of the international protocol. Correlation coefficients for the values obtained by the auscultatory method and from the developed device were 0.982 and 0.980 for systolic and diastolic blood pressure, respectively. Blood pressure measurements based on Korotkoff sound signals obtained by using the developed PVDF film-based sensor module are accurate and highly correlated with measurements obtained by the traditional auscultatory method.

• Journal of Sensor Science and Technology
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• v.33 no.3
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• pp.165-172
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• 2024

In this study, we investigated the detection properties of piezoresistive carbon nanotubes/polydimethylsiloxane (CNT/PDMS) devices with porous structures under applied pressure. The device, having dimensions of 10 mm × 10 mm × 5 mm, was fabricated with a porosity of 74.5%. To fabricate piezoresistive CNT/PDMS devices, CNTs were added using two different methods. In the first method, the CNTs were mixed with PDMS before the fabrication of the porous structure, while in the second, the CNTs were coated after the fabrication of the porous structure. Various detection properties of the fabricated devices were examined at different applied pressures. The CNT-coated device exhibited stable outputs with lesser variation than the CNT-mixed device. Moreover, the CNT-coated device exhibited improved reaction properties. The response time of the CNT-coated device was 1 min, which was approximately about 20 times faster than that of the CNT-mixed device. Considering these properties, CNT-coated devices are more suitable for sensing devices. To verify the CNT-coated device as a real sensor, it was applied to the gripping sensor system. A multichannel sensor system was used to measure the pressure distribution of the gripping sensor system. Under various gripping conditions, this system successfully measured the distributed pressures and exhibited stable dynamic responses.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.673-677
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• 2016

In this study, In order to measure foot pressure, it makes analyzing device using multi-pressure sensor. This device was limited frequency band to 5Hz by using low-pass filter and MCU was detected signal every milliseconds. After wearing the device, the result was confirmed by blue-tooth to measure wirelessly. Also, we propose an algorithm to obtain the walking pattern using a time table in each of the detected peak from the pressure sensor. Using the algorithm, right walking pattern and abnormal pattern was detected. The results can be reflected more individual walking patterns than when using a conventional methods and also, developed device was no restriction on the human activity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.3
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• pp.487-492
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• 2016

In this paper, a device for analyzing the pressure distribution during walking was produced by using the pressure sensor on the heel. This device was limited to a frequency band by using the 1st low-pass filter. And an algorithm to analyze the value of the quantity to pressure using a analog to digital converter. It is used by using the threshold voltage of pressure sensor, it is suggested the algorithm. The algorithm is detected the peak which is exceeded the threshold voltage. and thus in accordance, it is detected the number of steps. And the calorie consumption were detected by using it. Also it used an MCU and Bluetooth. And by confirming the data at the LCD of the other MCU, it was to reduce the size of the device. According to this algorithm, it has the advantage that there is no restriction on the activity than when using an imaging device and it is inexpensive than other sensors such as an acceleration sensor or a gyro and it is easy to handle.

• Journal of Korea Multimedia Society
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• v.25 no.9
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• pp.1307-1315
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• 2022

In this paper, we proposed and developed a new portable skin elasticity measuring device based on the indentation method using piezoelectric effect. The proposed device is designed to minimize the uncertainty caused by the layer structure of the skin when measuring the elasticity of the skin. And, we developed a piezoelectric-based thin-film pressure sensor that can measure quantitatively and quickly during repeated measurement as a device sensor. To confirm the effectiveness of the proposed measuring device, it was compared with the experimental results of the conventional measuring devices under the same experimental conditions, and statistical correlation analysis was performed between the experimental data of the proposed measuring device and the experimental data of the conventional measuring devices. As a result of the correlation analysis, it was confirmed that the proposed measuring device had a high correlation with the conventional measuring devices. Therefore, it was confirmed that the proposed skin elasticity measuring device was effective.

• Physical Therapy Rehabilitation Science
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• v.12 no.3
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• pp.251-258
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• 2023

Objective: The practice of breathing exercises involves altering the depth and frequency of respiration. Strengthening respiratory muscles plays a crucial role in maintaining overall health and well-being. The efficiency of the respiratory system affects not only physical activity but also various physiological processes including cardiovascular health, lung function, and cognitive abilities. The study evaluated the reliability of the developed device for inspiratory/expiratory training using pressure sensors and Bluetooth connectivity with a smartphone application. Design: Design & development research Methods: The research methodology involved connecting a custom-made respiratory sensor to an IMT-PEP BIC Breath device. Various pressure conditions were measured, and statistical analyses were performed to assess reliability and consistency. Results showed high Intraclass Coefficient Correlation (ICC) values for both inspiratory and expiratory pressures, indicating strong test-retest reliability. The device was designed for ease of use and wireless monitoring through a smartphone app. Results: This study conducted at expiratory pressure confirmed the proper operation of the IMT/PEP breathing trainer at the specified pressure setting in the product. The pressure sensor demonstrated high test-retest reliability with an ICC value of 0.999 for both expiratory and inspiratory pressure measurements. Conclusions: The developed respiratory training device measured and monitored inspiratory and expiratory pressures, demonstrating its reliability for respiratory training. The system could be utilized to record training frequency and intensity, providing potential benefits for patients requiring respiratory interventions. Further research is needed to assess the full potential of the device in diverse populations and applications.

• Journal of Mechanical Science and Technology
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• v.20 no.4
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• pp.505-512
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• 2006

This paper presents an integrated multifunctional sensor based on MEMS technology, which can be used or embedded in mobile devices for environmental monitoring. An absolute pressure sensor, a temperature sensor and a humidity sensor are integrated in one silicon chip of which the size is $5mm\times5mm$. The pressure sensor uses a bulk-micromachined diaphragm structure with the piezoresistors. For temperature sensing, a silicon temperature sensor based on the spreading-resistance principle is designed and fabricated. The humidity sensor is a capacitive humidity sensor which has the polyimide film and interdigitated capacitance electrodes. The different piezoresistive orientation is used for the pressure and temperature sensor to avoid the interference between sensors. Each sensor shows good sensor characteristics except for the humidity sensor. However, the linearity and hysteresis of the humidity sensor can be improved by selecting the proper polymer materials and structures.