Wearable Resistive Pressure Sensor Based on Highly Flexible Carbon Composite Conductors with Irregular Surface Morphology

Kim, Kang-Hyun,Hong, Soon Kyu,Jang, Nam-Su,Ha, Sung-Hun,Lee, Hyung Woo,Kim, Jong-Man American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.20

<P>Wearable pressure sensors are crucial building blocks for potential applications in real-time health monitoring, artificial electronic skins, and human to machine interfaces. Here we present a highly sensitive, simple-architectured wearable resistive pressure sensor based on highly compliant yet robust carbon composite conductors made of a vertically aligned carbon nanotube (VACNT) forest embedded in a polydimethylsiloxane (PDMS) matrix with irregular surface morphology. A roughened surface of the VACNT/PDMS composite conductor is simply formed using a sandblasted ' silicon master in a low-cost and potentially scalable manner and plays an important role in improving the sensitivity of resistive pressure sensor. After assembling two of the roughened composite conductors, our sensor shows considerable pressure sensitivity of similar to 0.3 kPa(-1) up to 0.7 kPa as well as stable steady-state responses under various pressures, a wide detectable range of up to 5 kPa before saturation, a relatively fast response time of similar to 162 ms, and good reproducibility over 5000 cycles of pressure loading/unloading. The fabricated pressure sensor can be;used to detect a wide rang of human motions ranging from subtle blood pulses to dynamic joint movements, and it can also be used to map spatial pressure distribution in a multipixel platform (in a 4 X 4 pixel array).</P>

Effect of Fabric Structure on the Performance of 3D Woven Pressure Sensor

Khubab Shaker,Muhammad Umair,Syed Talha Ali Hamdani,Yasir Nawab 한국섬유공학회 2021 Fibers and polymers Vol.22 No.3

The textile-based pressure sensors are an integral part of the wearable electronic textiles, that helps to measure thepressure/load applied to the sensor. These sensors are used predominantly for health and sports application, especially tomonitor the blood pressure, heart rate or performance of muscles during exercise. The work done in this research is about theinvestigation of the response of a 3D woven fabric-based pressure sensor by varying the yarn interlacement pattern in 3layered fabric. Four samples were produced using a 3D weaving technique, with two types of yarns i.e. polyester/cotton (59tex) and multifilament steel (55.5 tex). The weave design of face and back layer of the three-layered structure was kept 1/1plain (P), while the weave design of middle layer was changed to plain (P), matt (M), twill (T) or satin (S), resulting instructures PPP, PMP, PTP, and PSP respectively. Working of pressure sensor was evaluated in terms of resistance offered bystructure, both under static and dynamic loading. The dynamic load was applied by the compression and subsequentrelaxation, i.e. under incremental loading followed by decremental unloading. All the structures showed variation inresistance in response to applied load showing potential being used as a pressure sensor. The structures PPP, PMP, and PSPbehaved as a pressure sensor up to 500 grams while the efficient sensor was PTP (plain/twill/plain) with activity up to a loadof 5500 grams. A statistical model was developed for the structure PTP, correlating the resistance with the applied load. Thedeveloped sensors can also be produced inside the fabrics or can be embedded inside garments.

압력스위치 어레이를 이용한 마이크로 압력센서

박중호(Jung-Ho Park),윤동원(Dong-Won Youn),이동원(Dong-Weon Lee),함상용(Sang-Yong Ham),조정대(Jeong-Dai Jo) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

A novel MEMS pressure sensor using resistance change of pressure switch array is proposed and developed. It consists of a silicon substrate that has a thin metal-deposited diaphragm and a pressure switch array patterned on Pyrex glass. Pressure switch array is formed by connecting serially a few of electrodes and resistances. When the pressure is applied, the change of the contact area due to the diaphragm deformation is converted to sensor output through an electric signal circuit. To form the metal-deposited diaphragm and the pressure switch array, fabrication process using micromachining technologies is presented. Then, simulation results such as a stress analysis of the diaphragm and contact area characteristics with an applied pressure are presented and several methods for linearity compensation are discussed. Furthermore, basic characteristics of the fabricated prototype are experimentally investigated and the validity of the proposed pressure sensor is verified.

An impedance tunable and highly efficient triboelectric nanogenerator for large-scale, ultra-sensitive pressure sensing applications

Rasel, M. Salauddin,Maharjan, Pukar,Salauddin, Md.,Rahman, M. Toyabur,Cho, Hyun Ok,Kim, Jae Woo,Park, Jae Yeong Elsevier 2018 Nano energy Vol.49 No.-

<P><B>Abstract</B></P> <P>Precise triboelectric nanogenerators (TENGs) with large-scale pressure sensing ability can be realized by effectively harvesting physical pressure. Extensive research on efficient pressure sensors is ongoing, yet the pressure detection limit and sensitivity of most of the reported pressure sensors are not satisfactory for practical and wearable device applications. Herein, we demonstrate a highly efficient approach toward detecting a wide range of pressures, from 5 kPa to 450 kPa, with a record high sensitivity of 0.51 V/kPa. We aim at maximizing the energy conversion efficiency of 48.17% by optimally tuning the internal impedance of the triboelectric nanogenerator at 2.5 MΩ, because low internal impedance results in high output power. This paper reports the structural design, fabrication, and experimental validation of a self-powered and highly durable TENG pressure sensor for large-scale pressure detection based on double-side tribological layers of micro-patterned polydimethylsiloxane (PDMS) and PDMS-multiwall carbon nanotube (CNT) nanocomposites. An in-sole application of the proposed TENG is demonstrated for varying foot pressures corresponding to different walking patterns, which is likely to be applicable in sports sciences, high-risk diabetic foot ulceration, and rehabilitation. Our present contribution not only facilitates large-scale pressure sensing but also paves the way toward the realization of next-generation self-powered and maintenance-free sensing devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A self-powered triboelectric nanogenerator with record high pressure detection range (From 5 kPa to 450 kPa). </LI> <LI> A maximum of 0.51 V/kPa sensitivity. </LI> <LI> Up to 48.17% energy conversion efficiency. </LI> <LI> Low internal impedance of 2.5 MΩ. </LI> <LI> In-sole application. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

생체신호 모니터링을 위한 CNT 기반 스페이서 직물 압력센서 구현 및 센싱 능력 평가

윤하영 ( Ha-yeong Yun ),김상운 ( Sang-un Kim ),김주용 ( Joo-yong Kim ) 한국감성과학회 2021 감성과학 Vol.24 No.2

With recent innovations in the ICT industry, the demand for wearable sensing devices to recognize and respond to biological signals has increased. In this study, a three-dimensional (3D) spacer fabric was embedded in a single-wall carbon nanotube (SWCNT) dispersive solution through a simple penetration process to develop a monolayer piezoresistive pressure sensor. To induce electrical conductivity in the 3D spacer fabric, samples were immersed in the SWCNT dispersive solution and dried. To determine the electrical properties of the impregnated specimen, a universal testing machine and multimeter were used to measure the resistance of the pressure change. Moreover, to examine the changes in the electrical properties of the sensor, its performance was evaluated by varying the concentration, number of penetrations, and thickness of the specimen. Samples that penetrated twice in the SWCNT distributed solution of 0.1 wt% showed the best performance as sensors. The 7-mm thick sensors showed the highest GF, and the 13-mm thick sensors showed the widest operating range. This study confirms the effectiveness of the simple process of fabricating smart textile sensors comprising 3D spacer fabrics and the excellent performance of the sensors.

전도성 다공성 구조 압력감지소자

소혜미(Hye-Mi So),박철민(Cheolmin Park),장원석(Won Seok Chang) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.7

일반적으로 표면적/부피비가 큰 전도성 다공체는 수퍼캐패시터의 전극이나 흡수제, 유연히터 등의 다양한 분야에 적용되어 왔다. 본 논문에서는 이러한 전도성 다공성 구조의 역학적·전기적 특성을 이용하여 고감도 압력센서를 구현하였다. 탄소나노튜브 용액에 스펀지를 적셔 다공체에 전도성을 부여하였으며, 압력에 따른 전도성 다공체의 저항 변화를 측정하였다. 전도성 스펀지에 압력이 가해졌을 때, 각각의 탄소나노튜브들은 서로 맞붙게 되어 저항이 최대 20%까지 줄어듦을 확인하였다. 부드럽고 탄성력이 뛰어난 탄소나노튜브 스폰지는 반복적인 압축실험에도 모양의 변형 없이 매우 빠르게 안정화되고 일정한 저항변화를 확인할 수 있었다. 또한 스펀지 압력소자를 유연소자에 적용하기 위하여 탄소나노튜브 트랜지스터와 연결하여 외부압력에 따른 전기적 특성변화를 측정하였다. Porous conductors are known to demonstrate excellent electrical, mechanical, and chemical resistance. These porous conductors demonstrated potential applications in various fields such as electrodes for supercapacitors, flexible heaters, catalytic electrodes, and sorbents. In this study, we described a pressure sensitive device using conductive and porous sponges. With an extremely simple “dipping and drying” process using a single-walled carbon nanotube (SWCNT) solution, we produced conductive sponges with sheet resistance of < 30 kΩ/sq. These carbon nanotube sponges can be deformed into any shape elastically and repeatedly compressed to large strains without collapse. The pressure sensors developed from these sponges demonstrated high resistance change under pressure of up to a half of their initial resistance.

압저항체에서 발생하는 잔류응력이 저항변화율 분포도에 미치는 영향성 평가

심재준(J. J. Shim),한근조(G. J. Han),이성욱(S. W. Lee),이상석(S. S. Lee) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월

In these days, the piezoresistive material has been applied to various sensors in order to measure the change of physical quantities. But the relationship between the sensitivity of a sensor and the position and size of piezoresistor has rarely been studied. Therefore, this paper was focused on the effect of residual stress induced in piezoresistor on the distribution of resistance change ratio and supposed the feasible position of piezoresistor. The resulting are following; The tensile residual stress in the vicinity of piezoresistor decreased the value of resistance change ratio and could not effect on all the area of diaphragm but local area around the piezoresistor. Also, the piezoresistor in the diaphragm type pressure sensor with boss should fabricate in the edge of boss in order to increase the sensitivity of pressure sensor.

Pd 박막의 전기저항-수소농도 이력현상

이은송이 ( Eunsongyi Lee ),이준민 ( Jun Min Lee ),전계진 ( Kye Jin Jeon ),이우영 ( Woo Young Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 2009 대한금속·재료학회지 Vol.47 No.6

We report on hysteresis behavior in the electrical resistance-hydrogen concentration of Pd thin films. The variation of the electrical resistance has been investigated during the process of absorption and desorption of hydrogen gas (H2) as a function of thickness of Pd thin films. The hysteresis behavior in the electrical resistance with H2 concentration was found for Pd thin films and consists of α phase, α+β phase, and β phase regions. The sensitivity of Pd thin films with H2 concentration was found to follow Sieverts` law in the α phase region. However, the sensitivity was observed to increase abruptly with H2 concentration in the α+β phase co-exist region. This is because Pd-H interaction is stronger in the β phase than in the α phase and needs a higher concentration gradient as a driving force to desorb. The formation of the β phase also was observed to cause the structural change because of the lattice expansion during absorption. The hysteresis height and the trace of structural change were affected by the thickness of the Pd film. As the film becomes thinner, the hysteresis height becomes lower and the amount of delamination on the surface becomes smaller. For films thinner than 20 nm in thickness, the delamination was not found but electrical resistance hysteresis was still observed. (Received December 22, 2008)

맥 센서 어레이(array)의 실리콘(silicone) 코팅 두께에 따른 센서 간 간섭효과

전민호 ( Min Ho Jun ),전영주 ( Young Ju Jeon ),김영민 ( Young Min Kim ) 한국센서학회 2016 센서학회지 Vol.25 No.1

Pulse diagnosis is one of the representative diagnostic methods in Oriental medicine. In this study, a pulse pressure sensor array coated with silicone, which includes 6 piezo-resistive sensors and 1 thermistor, is fabricated for pulse measurement. It is necessary to coat the pulse sensor array with silicone to avoid the fracture or damage of pressure sensors when the sensor is in contact with the skin and a constant pressure is applied. However, the silicone coating on the pulse sensor array can cause signal interference among the sensors in the pulse sensor array. The interference number (IN), a calculation for expressing the degree of interference among channels, is changed according to the silicone thickness on the pulse sensor array. The IN is increased by a thick silicone coating, but the fabrication error, an important index for the mass production of the sensor array, is reduced by the thickness of the silicone coating. We propose that the thickness of the silicone on the pulse sensor array is an important consideration for the performance of the fabricated sensor and manufacturing repeatability.

압저항형 스트레인 게이지를 이용한 압력센서의 개발

이동훈(Lee Dong-Hoon),강민성(Kang Min-Sung),허용(Huh Yong),구재민(Koo Jae-Mean),석창성(Seok Chang-Sung) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

A pressure sensor is a sensing device to perceive inputing pressure and convert pressure with an electric signal. Currently, a domestic pressure sensor mostly uses mechanical methods. So, it uses many parts and its cost is high. Therefore, It is necessary to improve the weak points of an existing pressure sensor and develop the accurate and reliable pressure sensor using piezo resistance strain gages.