Polyurethane sponges decorated with reduced graphene oxide and silver nanowires for highly stretchable gas sensors

Luan, Yange,Zhang, Shaolin,Nguyen, Thuy Hang,Yang, Woochul,Noh, Jin-Seo Elsevier 2018 Sensors and actuators. B Chemical Vol.265 No.-

<P><B>Abstract</B></P> <P>Unlike the stretchable physical sensors such as stretchable pressure sensors, strain sensors, and temperature sensors, few works have been reported on the stretchable gas sensors. This study presents that stretchable gas sensors can be fabricated by decorating reduced graphene oxide/silver nanowires (rGO/AgNWs) hybrids on the porous polyurethane (PU) sponges using a facile dip-coating method. The sensors show good room-temperature responses to NO<SUB>2</SUB> gas under both a bending strain (r = 3 mm) and a large tensile strain up to 60%. The response of about −15% is measured at a 50 ppm of NO<SUB>2</SUB> under a 60% strain. Furthermore, reducing gases like acetone and ethanol can also be detected under the large strains. The results of this study offer a new insight into realization of highly stretchable and easy-to-fabricate gas sensors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly stretchable gas sensors are fabricated by the dip-coating method. </LI> <LI> The electrical properties of the sensors can be easily tuned. </LI> <LI> The sensors can detect an oxidizing gas, NO<SUB>2</SUB>, and reducing gases, acetone and ethanol. </LI> <LI> The stretchable gas sensors work stably even under large strains up to 60%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Design and Preliminary Evaluation of High-Temperature Position Sensors for Aerospace Applications

Yongdae Kim,Hyun Young Choi,Young Cheol Lee IEEE 2014 IEEE SENSORS JOURNAL Vol.14 No.11

<P>In this paper, high-temperature position sensors for aerospace applications are proposed and geometric design improvements to enhance the performance of the proposed position sensors are derived. Position sensors comprise a resistive element, a conductive brush that moves along the resistive element, and the electrodes at each end of the element. In design of conventional position sensors, the resistive elements are exposed to the atmosphere. This exposure results in oxidation and a chemical reaction with ambient gas at a high temperature. Furthermore, the resistive elements can be damaged by the brush, which is in direct contact with the surface of the resistive element. Materials used for the resistive element, electrode, and substrate limit high-temperature applications of conventional position sensors. To overcome these disadvantages associated with conventional position sensors, novel position sensors were designed that focus on the protection of the resistive elements and the selection of high-temperature materials for the resistive element, electrode, and substrate. The spatial resolution of the proposed position sensors can be improved by densely integrating the patterns of the position sensors using the planar process, which is used to realize microelectromechanical systems and IC devices. In this paper, two types of position sensors were fabricated, and a preliminary performance evaluation at room temperature was carried out in order to validate the concept of the proposed potentiometers; the results of the performance test are presented in this paper.</P>

웨어러블 생체신호 모니터링을 위한 스마트텍스타일센서의 분류 및 고찰

장은지 ( Eunji Jang ),조길수 ( Gilsoo Cho ) 한국의류산업학회 2019 한국의류산업학회지 Vol.21 No.6

This review paper deals with materials, classification, and a current article investigation on smart textile sensors for wearable vital signs monitoring (WVSM). Smart textile sensors can lose electrical conductivity during vital signs monitoring when applying them to clothing. Because they should have to endure severe conditions (bending, folding, and distortion) when wearing. Imparting electrical conductivity for application is a critical consideration when manufacturing smart textile sensors. Smart textile sensors fabricate by utilizing electro-conductive materials such as metals, allotrope of carbon, and intrinsically conductive polymers (ICPs). It classifies as performance level, fabric structure, intrinsic/extrinsic modification, and sensing mechanism. The classification of smart textile sensors by sensing mechanism includes pressure/force sensors, strain sensors, electrodes, optical sensors, biosensors, and temperature/humidity sensors. In the previous study, pressure/force sensors perform well despite the small capacitance changes of 1-2 pF. Strain sensors work reliably at 1 kΩ/cm or lower. Electrodes require an electrical resistance of less than 10 Ω/cm. Optical sensors using plastic optical fibers (POF) coupled with light sources need light in-coupling efficiency values that are over 40%. Biosensors can quantify by wicking rate and/or colorimetry as the reactivity between the bioreceptor and transducer. Temperature/humidity sensors require actuating triggers that show the flap opening of shape memory polymer or with a color-changing time of thermochromic pigment lower than 17 seconds.

Hybrid Sensor Calibration Scheme for Mobile Crowdsensing–Based City-Scale Environmental Measurements

손승철,이병탁,고석갑,강경란 한국전자통신연구원 2016 ETRI Journal Vol.38 No.3

In this paper, we propose a hybrid sensor calibration scheme for mobile crowdsensing applications. As the number of newly produced mobile devices containing embedded sensors continues to rise, the potential to use mobile devices as a sensor data source increases. However, because mobile device sensors are generally of a lower performance and cost than dedicated sensors, sensor calibration is crucial. To enable more accurate measurements of natural phenomena through the use of mobile device sensors, we propose a hybrid sensor calibration scheme for such sensors; the scheme makes use of mobile device sensors and existing sensing infrastructure, such as weather stations, to obtain dense data. Simulation results show that the proposed scheme supports low mean square errors. As a practical application of our proposed scheme, we built a temperature map of a city using six mobile phone sensors and six reference sensors. Thanks to the mobility of the sensors and the proposed scheme, our map presents more detailed information than infrastructure-based measurements.

Plasmonic colorimetric sensors based on etching and growth of noble metal nanoparticles: Strategies and applications

Zhang, Zhiyang,Wang, Han,Chen, Zhaopeng,Wang, Xiaoyan,Choo, Jaebum,Chen, Lingxin Elsevier 2018 Biosensors & bioelectronics Vol.114 No.-

<P><B>Abstract</B></P> <P>Plasmonic colorimetric sensors have emerged as a powerful tool in chemical and biological sensing applications due to the localized surface plasmon resonance (LSPR) extinction in the visible range. Among the plasmonic sensors, the most famous sensing mode is the “aggregation” plasmonic colorimetric sensor which is based on plasmon coupling due to nanoparticle aggregation. Herein, this review focuses on the newly-developing plasmonic colorimetric sensing mode – the etching or the growth of metal nanoparticles induces plasmon changes, namely, “non-aggregation” plasmonic colorimetric sensor. This type of sensors has attracted increasing interest because of their exciting properties of high sensitivity, multi-color changes, and applicability to make a test strip. Of particular interest, the test strip by immobilization of nanoparticles on the substrate can avoid the influence of nanoparticle auto-aggregation and increase the simplicity in storage and use. Although there are many excellent reviews available that describe the advance of plasmonic sensors, limited attention has been paid to the plasmonic colorimetric sensors based on etching or growth of metal nanoparticles. This review highlights recent progress on strategies and application of “non-aggregation” plasmonic colorimetric sensors. We also provide some personal insights into current challenges associated with “non-aggregation” plasmonic colorimetric sensors and propose future research directions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The strategies for plasmonic colorimetric sensors based on nanoparticles etching/growth are reviewed. </LI> <LI> Highlighted applications in environmental as well as biological analysis are provided. </LI> <LI> The advantages and future directions of this kind of sensing platforms are detailed discussed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Plasmonic colorimetric sensors based on etching and growth of noble metal nanoparticles.</P> <P>[DISPLAY OMISSION]</P>

Effects of Long-term Exposure of High and Low Humidity on Thin-film Humidity Sensors

( Sang-wook Lee ),( Byung Il Choi ),( Jong Chul Kim ),( Sang-bong Woo ) 한국센서학회 2018 센서학회지 Vol.27 No.6

The effects of long-term exposure of high and low humidity on thin-film humidity sensors are investigated. Five commercially available thin-film humidity sensors are initially calibrated in a humidity chamber as a reference before longterm exposure to high and low humidity. Then, the sensors are kept in a high-humidity environment (~95 %rh) for four months. After the exposure, the sensors are calibrated in the same manner as the initial calibration. Consequently, the device reading values from the humidity sensors are elevated up to about 5 %rh. Interestingly, the degree of elevation by the high-humidity exposure shows a negative correlation with the price of the humidity sensors. Humidity sensors are then kept in a low-humidity environment (~10 %rh) for another four months. After the exposure, a calibration similar to the initial calibration is performed. As a result, the device reading from humidity sensors is decreased, indicating a recovery from the effect of high-humidity exposure. The durability test conducted in this study provides experimental evidence for the use of thin-film humidity sensors in high-humidity environments such as greenhouses and food factories for a long period of time.

Material Approaches to Stretchable Strain Sensors

Park, Jaeyoon,You, Insang,Shin, Sangbaie,Jeong, Unyong WILEY‐VCH Verlag 2015 ChemPhysChem Vol.16 No.6

<P><B>Abstract</B></P><P>With the recent progress made in wearable electronics, devices now require high flexibility and stretchability up to large strain levels (typically larger than 30 % strain). Wearable strain sensors or deformable strain sensors have been gaining increasing research interest because of the rapid development of electronic skins and robotics and because of their biomedical applications. Conventional brittle strain sensors made of metals and piezoresistors are not applicable for such stretchable sensors. This Review summarizes recent advances in stretchable sensors and focuses on material aspects for high stretchability and sensitivity. It begins with a brief introduction to the Wheatstone bridge circuit of conventional resistive strain sensors. Then, studies on the manipulation of materials are reviewed, including waved structural approaches for making metals and semiconductors stretchable, the use of liquid metals, and conductive filler/elastomer composites by using percolation among the fillers. For capacitive strain sensors, the constant conductivity of the electrode is a key factor in obtaining reliable sensors. Possible approaches to developing capacitive strain sensors are presented. This Review concludes with a discussion on the major challenges and perspectives related to stretchable strain sensors.</P>

LOCALIZATION OF A RAIL ROBOT IN GREENHOUSE BASED ON MULTI-SENSORS

Chao Chang,Yan Li,Jang-Myung Lee 제어로봇시스템학회 2010 제어로봇시스템학회 국내학술대회 논문집 Vol.2010 No.5

In this paper, we present a method for localization of a rail Autonomous Pesticide Spraying Robot for working in greenhouse using a multi-sensors system. The proposed localization method utilizes ultrasonic, inductive proximity and vision sensors. The vision sensors are used to gather the plant image, the edge of plants can gain through the image segmentation algorithm and the edge detection algorithm. And ultrasonic sensors supply the distance information from the greenhouse walls to the robot. After fusing the data of vision sensors and ultrasonic sensors, the edge of entire rows of plant could be measured. The inductive proximity sensors supply the position information from the robot to the edge and turning of rail. By processing the signals coming from these sensors, it can be identified the position relatives between the robot and the plant. The robot is designed for eliminating pests which live on plant leaves precisely. On the basis of the position relatives, the robot executes different operations, such as running, beginning scanning leaf, stopping scanning and so on. Experiments demonstrate the effectiveness of the proposed method in real world applications.

Suspended black phosphorus nanosheet gas sensors

Lee, Geonyeop,Kim, Suhyun,Jung, Sunwoo,Jang, Soohwan,Kim, Jihyun Elsevier 2017 Sensors and actuators. B, Chemical Vol.250 No.-

<P><B>Abstract</B></P> <P>The studies on enhancing the sensitivities of chemical sensors based on two-dimensional (2D) materials have been focused primarily on surface modifications including defect engineering, chemical doping, and incorporation of metal nanoparticles. Exfoliated black phosphorus (BP), which is one of the 2D materials, has attracted considerable attention because it offers higher sensitivity than other 2D materials (e.g., graphene and MoS<SUB>2</SUB>). In this study, for the first time, we attempt to increase the performance of BP chemical sensors to their theoretical limit by floating BP flakes on top of electrode posts in order to provide full (both sides) adsorption sites and avoid interface scattering effects. Our suspended BP gas sensors fabricated <I>via</I> dry transfer showed higher sensing performances than the conventional supported BP gas sensors (gas response was increased by approximately 23% at 200ppm). In addition, faster response and recovery with high reproducibility were observed in suspended BP chemicals sensors than in the supported ones. Our work reveals the full potential of pristine BP-based chemical sensors and paves the way for the next-generation high performance 2D chemical sensors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We demonstrated the suspended 2D black phosphorus gas sensors with superior sensing performance. </LI> <LI> Suspended 2D structure has a high surface-to-volume ratio and adsorption areas on both sides. </LI> <LI> Suspended 2D sensor exhibited a faster desorption rate than the supported one. </LI> <LI> Sensitivity was increased by approximately 23% at 200ppm. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

초음파센서와 관성센서를 이용한 발의 움직임 추적 시스템

부장훈(Jang Hun Boo),박상경(Sang Kyeong Park),서영수(Young Soo Suh) 제어로봇시스템학회 2010 제어·로봇·시스템학회 논문지 Vol.16 No.11

This paper presents a foot movement tracking system using ultrasonic sensors and inertial sensors, where the position and velocity of foot are computed using inertial sensors and ultrasonic sensors mounted on a shoe. A foot movement can be estimated using an inertial navigation algorithm only; however, the error tends to increase due to biases of gyroscopes and accelerometers. To reduce the error, a localization system using ultrasonic sensors is additionally used. In the localization system using ultrasonic sensors, the position is continuously calculated in the absolute coordinate. An indirect Kalman filter is used to combine inertial sensors and ultrasonic sensors. Through experiments, it is shown that the proposed system can track a foot movement.