Efficient Integration of Barometric Pressure Sensors and Si FET-type Gas Sensors on the Same Substrate

장동규 서울대학교 대학원 2020 국내박사

Sensor technology is becoming increasingly important to improve the quality of human life. Especially, various kinds of sensor technology have become essential due to increasing demand for smart mobile devices, automobiles and household appliances. Furthermore, as many types of sensors are installed on smart devices, it is more important to integrate different sensors in the IoT era. If multiple types of sensors are efficiently integrated with CMOS circuit on a single substrate, the footprint and power consumption could be reduced. Gas sensors are not only for detecting harmful gases, but also for improving indoor air quality and detecting diseases. The conventional resistor-type gas sensors have a simple structure and a simple manufacturing process, but they are large in size and have high power consumption. On the other hand, FET-type gas sensors can be fabricated very small in size and compatibly integrated with CMOS circuits, and they are easy to integrate with other types of sensors. In addition, built-in localized micro-heater can minimize power consumption of the FET-type gas sensors. In this dissertation, barometric pressure sensors and Si FET-type gas sensors are efficiently integrated on the same Si substrate using conventional MOSFET fabrication process. The barometric pressure sensors have built-in temperature sensors to accurately measure the atmospheric pressure according to the ambient temperature. In addition, the FET-type gas sensor has a localized micro-heater capable of heating up to 124 ºC with a power of 4 mW. NO2 gas sensing is successfully achieved with this gas sensor. Air-gap with a depth of 2.5 μm are formed in the Si substrate and used as the cavity for the barometric pressure sensor and as an insulating layer for the FET-type gas sensor. In addition, poly-Si with Boron ion implantation is used as the piezo-resistors of the barometric pressure sensor, the electrode of the temperature sensor, and the FG and micro-heater of the FET-type gas sensor at the same time. In this way, the barometric pressure sensors and the FET-type gas sensors are efficiently integrated using CMOS compatible fabrication process. The barometric pressure sensor has a built-in temperature sensor that can measure ambient temperature and atmospheric pressure at the same time. The measured atmospheric pressure varies with ambient temperature, but with a designed neural network, accurate atmospheric pressure can be obtained with an accuracy of 97.5 %. 사물 인터넷 (IoT) 시대를 맞이하여 삶의 질을 개선하기 위한 센서 기술들이 점차 중요해지고 있다. 특히, 각종 스마트 기기들을 비롯한 자동차 및 가전 제품에 대한 센서 기술들이 필수적이 되고 있다. 아울러, 다양한 종류의 센서들의 통합 및 집적 기술이 주목받고 있다. 여러 유형의 센서들을 단일 기판에서 CMOS 회로와 효율적으로 통합하면 전력 소모를 줄일 수 있으며, 제조 단가 또한 낮출 수 있다. 다양한 센서기술 중 가스 센서는 유해 가스 감지뿐만 아니라 실내 공기 질 개선 및 질병 감지에 사용될 것으로 예상된다. 종래의 저항 형 가스 센서는 구조가 간단하며 제조 공정이 단순하지만 크기가 크고 전력 소비가 높은 편이다. 한편, FET 형 가스 센서는 매우 작은 크기로 제작이 가능하며 CMOS 회로와 호환 가능하다. 또한 내장된 마이크로 히터 (Micro-Heater)를 사용하게 되면 FET 형 가스 센서의 전력 소비를 최소화 시킬 수 있다. 본 논문에서는 기압 센서와 Si FET 형 가스 센서를 MOSFET 제조 공정기술을 사용하여 단일 실리콘 (Silicon) 기판에 효율적으로 집적하였다. 제작된 기압 센서는 온도 센서를 내장하고 있어서 주변 온도에 따른 대기압을 정확하게 측정 가능하다. 또한 FET 형 가스 센서는 4 mW의 전력으로 최대 124 ˚C까지 가열 할 수 있는 국부화 된 마이크로 히터를 내장하고 있다. 이 가스 센서로 이산화 질소가스 (NO2)의 농도를 측정하였다. 2.5 μm 깊이의 에어 갭 (Air-gap)을 Si 기판에 형성하고 이 에어 갭은 기압 센서의 공동 (Cavity) 및 FET 형 가스 센서의 절연 층으로 사용하였다. 또한, 붕소(Boron) 이온을 주입한 다결정 실리콘 (Poly-Si)은 기압 센서 및 온도 센서의 전극, FET 형 가스 센서의 플로팅 게이트 (Floating-gate), 그리고 마이크로 히터의 전극으로 동시에 사용하였다. 이러한 방식으로 기압 센서, FET 형 가스센서는 CMOS 호환 제조 공정을 사용하여 효율적으로 단일기판에 집적하였다. 기압 센서는 주변 온도와 대기압을 동시에 측정 할 수 있는 온도 센서를 내장하고 있으며, 주변 온도에 따른 대기압을 신경망을 통하여 97.5 %의 정확도로 측정할 수 있다.

Highly sensitive pressure/strain sensor with nanowire composite for skin-attachable multifunctional electronics

주윤식 Seoul National University 2016 국내박사

In this dissertation, we describe the highly sensitive pressure/strain sensor with nanowire composite for skin-attachable and wearable electronics. Multiscale structured nanowire composite composed of silver nanowires (AgNWs) and polydimethylsiloxane (PDMS) was designed and fabricated for the high performance multifunctional sensor. Based on this multiscale structured nanowire composite, high performance pressure/strain sensors were fabricated and characterized. Nowadays, flexible and stretchable physical sensors such as pressure, strain, and temperature sensors have been widely investigated for the application to the wearable electronics. Especially, high performance pressure/strain sensors which show high sensitivity, fast response time, and high cycle stability are required. Due to these requirements, we developed the nanowire composite, the flexible and stretchable electrode, and introduced the multiscale structure with nanometer-sized rough surface and micrometer-sized wavy structure to the nanowire composite. By integrating this nanowire composite and polymeric dielectric layer/printed Ag electrode, we fabricated capacitive-type pressure sensors and arrays. High pressure sensitivity (S >3.8 kPa-1), fast response and relaxation time (t <0.15s), high cycle stability (1500-cycle of repeated loading/unloading of pressure and 5000-cycle of repeated bending with bending radius of 3mm), and multiple sensing such as pressure and bending were obtained. Nanowire composite with multiscale structure can be easily scaled up for a large area sensor array and sensor arrays with 3 × 3 and 5 × 5 pixels were fabricated. The sensor arrays can detect the spatial distribution of the applied pressure with the sensitivity as high as that of the single sensor. Wearable fingertip pressure sensor was fabricated to demonstrate the fingertip pressure sensing prototype device. We attached each pressure sensor on the four fingers except a little finger and measured the capacitance change by grabbing plastic beaker. We developed simple method to control the pressure sensitivity of the sensor. Simply, by controlling the mixing ratio of the matrix PDMS of the nanowire composite, we can tune the pressure sensitivity of the sensor. Three types of PDMS with different mixing ratio, a 5:1, 10:1, and 15:1 mixture of liquid PDMS and curing agent, were used to fabricate nanowire composites and sensors. Owing to the difference of Young’s modulus and the shape of the crest area of nanowire composites with different mixing ratio, pressure sensors showed different pressure sensitivity according to different mixing ratio. We investigated the highly bendable pressure sensor with high bending stability and pressure sensing ability in the bending state. By introducing bending sensing part beside the pressure sensing part, the bendable sensor can detect both pressure and bending and distinguish the pressure and bending. We used the surface functionalization method and the PDMS spacer to demonstrate the bendable sensor. Strong siloxane bonding between the surface functionalized bottom plane, PDMS spacers and patterned nanowire composite was obtained and based on this bonding, our sensor showed high bending stability. Pressure sensitivity of the bendable sensor was increased up to 9 kPa-1 owing to the air gap from the PDMS spacer. The bendable sensor can detect ultra-low pressure of 0.7 Pa and show fast response and relaxation time below 0.075s. Even in the bending state, the bendable sensor can detect the normal pressure. By using this bendable sensor, we fabricated the wearable sensor to measure the wrist pulse and vibration of smart phone. Sensor array was also fabricated and we estimated the pressure in the bending state by calculating the capacitance change. We demonstrated the pressure sensitive transistor (PST) by integrating the bendable sensor and prined single-walled carbon nanotube thin film transistor (SWCNT TFT). PST can be operated in low voltage below 5V and ultra-low power consumption of PST below 15 nW can be achieved (I_DS< 15nA, V_DS= -1V). By using the PST and commercially available electronic devices such as LED chip, resistor, OP amp and battery, we fabricated the user inter-active pressure sensing device and pulse monitoring device. Finally, we developed the stretchable multifunctional sensor which can detect the 3-axis force, the normal force and shear force, and strain by using nanowire composite for the application to the electronic skin. By introducing various sensing component to the sensing system, we can obtain multifunctional sensor to mimic human tactile receptors and skin. For the 3-axis sensing, four individual capacitive sensors composed single sensing cell. Our sensor can sense and distinguish the pressure and shear force by analyzing the capacitance change of four individual capacitive sensors. For the strain sensing, flat nanowire composite was used. During the stretching process, the flat nanowire composite was deformed and this deformation resulted in the resistance change of the flat nanowire composite. Our sensor can detect the strain by analyzing the resistance change of the flat nanowire composite.

Polymer-based Flexible Wide Range Pressure Sensors with Hierarchical Micro Structure

Dongik Oh DGIST 2021 국내석사

This paper reports the flexible piezoresistive pressure sensor equipped with multi-height microstructures, and their effects on sensor properties. Specifically, we have fabricated two different types of pressure sensors: 1) microdome structures via XeF2 isotropic etching and 2) micropyramid structures realized by using a KOH etched Si mold. Using the isotropic dry etch, we were able to realize the microdomes with a height distribution from 10μm to 20μm. This is because the etch rate differs from middle of the chip to the edge. For micropyramids, we simply implemented KOH etch to fabricate a set of structures with heights from 18μm to 60μm. In KOH etching, the height of micropyramids can be precisely controlled at lithography level. We have fabricated the polydimethylsiloxane (PDMS) substrate using silicon mold by adopting both silicon wet etching and silicon dry etching process, and implemented multi-wall carbon nanotube (MWCNT) as a conducting layer. By fabricating a selectively etched micropyramid flexible pressure sensor, performance evaluation of the sensor as a function of the number of multi-steps is performed. Our results show that the measurement sensitivity increases with the number of different heights of the microstructures. To improve the electrode stability, electroplating is performed to form a thin layer of Au on CNT electrodes. Such coating has dramatically improved the contact stability as well as the measurement sensitivity. The interdigital electrode design (IDE) is implemented for simpler electrical readout. For application, we have placed the sensor on an insole of shoe and tacked the walking motion of human. In addition, we have integrated our pressure sensor on a robotic gripper and measured the applied pressure upon grasping an object. The introduced multi-height microstructures and a detailed study on their effects on sensor performances can enable a next generation flexible sensor platform. 이 논문은 다단 마이크로 구조를 갖춘 압저항(Piezoresistive effect) 유연압력센서(Flexible Pressure Sensor)와 센서 속성에 미치는 영향을 제시한다. 압저항 센서 속성을 확인하기 위해 두 가지 유형의 압력센서를 제작했습니다. 1) XeF2 등방성 에칭(Isotropic Etching)을 활용한 마이크로 돔(Microdome) 구조와 2) KOH 이방성 에칭(Anisotropic Etching) Si 몰드를 사용하여 제작된 마이크로 피라미드(Miocropyramid) 구조입니다. 등방성 건식 식각을 사용하여 10 ~ 20μm 높이를 가진 마이크로 돔 구조를 구현하였습니다. 이는 에칭 속도가 몰드의 위치에 따라 에칭 속도가 달라 마이크로 돔 다단 구조를 제작할 수 있었습니다. 마이크로 피라미드 구조의 경우 KOH 식각을 사용하여 18 ~ 60μm 높이의 구조를 단일 몰드에 제작하였습니다. KOH 에칭에서는 마이크로 피라미드 높이를 포토공정 수준에서 마스크 디자인을 통해 정밀하게 제어할 수 있습니다. 실리콘 습식 식각과 실리콘 건식 식각 공정을 모두 채택하여 실리콘 몰드를 이용하여 PDMS (Polydimethylsiloxane) 기판을 제작하고 활성 물질 층(Active Material Layer)으로 MWCNT(Multi-wall Carbon Nanotube)를 구현하였습니다. 선택적으로 식각 된 다단 마이크로 피라미드 구조 압력 센서를 제작함으로써 다단 수에 따른 센서의 성능평가가 진행되었습니다. 미세 구조의 높이가 다양할수록 측정 감도(Sensitivity)가 증가하고 피라미드의 크기가 커질수록 측정할 수 있는 범위(Detection Range)가 넓어진다는 결과를 보여주었습니다. 전극 안정성을 향상시키기 위해 전기도금(Electroplating)을 수행하여 CNT 전극에 얇은 Au 층을 형성합니다. 이러한 코팅은 접촉 안정성과 측정 감도를 크게 향상시킬 수 있습니다. IDE(Interdigital Electrode)는 보다 간단한 전기 판독을 위해 구현됩니다. IDE 구조 또한 전극을 Au로 사용하기 때문에 기존의 CNT로 사용된 센서보다 더 높은 민감도를 보여줍니다. 센서의 어플리케이션을 보기 위해 센서를 신발 깔창(Insole)에 붙어 실제 인간이 걷는 모습을 느낄 수 있게 모사하였습니다. 또한 로봇 그리퍼(Gripper)에 압력 센서를 통합하고 물체를 잡을 때 가해지는 압력을 측정했습니다. 도입 된 다중 높이 마이크로 구조와 센서 성능에 미치는 영향에 대한 연구는 차세대 유연한 센서 플랫폼에 적용할 수 있을 것으로 기대합니다.

Study of Porous Dielectric Elastomer Based Capacitive Pressure Sensor for Wearable Health Care Monitoring Applications : Study of Porous Dielectric Elastomer Based Capacitive Pressure Sensor for Wearable Health Care Monitoring Applications

박성원 광운대학교 2016 국내석사

As the average life expectancy of the world’s population increases, people’s interest in health care monitoring is growing. However, the existing health care monitoring system is inconvenient because it requires large machines, complex management, expensive price, and the user’s continuous care. In order to overcome these limitations, now a days a real-time health care monitoring system is being widely investigated. Many vital signals can be measured from inside and outside the human ody, such as ECG (electrocardiography), EMG (electromyography), blood pressure, etc. Among these signals, we have focused on gait signals and breathing signals. The gait signal is analyzed during walking, one of the most basic activities that humans have been doing since very long ago. Gait signal analysis is an evaluation of person’s gait, which helps athletes to run more efficiently and is used not only in sports biomechanics to identify posture-related or exercise-related problems of injured people, but also in distance, speed, momentum, and health status. It can also be used to diagnose specific diseases such as Parkinson’s disease and dementia. Breathing is the only way that or people inhale supplying oxygen to the blood for life support. Normal breathing is an essential part of a healthy life, and a variety of disease can be suspected depending on the amount and type of breathing. Asthma and sleep apnea, the most common respiratory diseases in the world, can be diagnosed by breathing signal analysis. Both gait and breathing signals have a commonality in causing pressure change around them. Based on this phenomenon, we have developed a wearable real-time healthcare device using these pressure sensors. Firstly, capacitive flexible pressure sensors were fabricated and demonstrated for a wearable health care monitoring applications. Generally, capacitive pressure sensors consist of two electrodes and a dielectric layer between them. PDMS (Polydimethylsiloxane) is a widely used as a dielectric layer material because of its high chemical and thermal stability, tunable elasticity, high dielectric constant and good recovery property. However, PDMS has high Young’s modulus, which may cause poor sensitivity in low pressure range. To overcome this limitation, we have developed micro porous structured PDMS using a sugar cube melting method. Because of the micro pores inside the PDMS dielectric layer, the pressure sensor can achieve high sensitivity in low pressure range. For the electrodes of the as designed pressure sensor, we made PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)) wrapped MWCNT (multi walled carbon nano tube) composite and deposited on top of the nylon filter paper using vacuum filtering method. After that, capacitive pressure sensor was completed by putting porous PDMS dielectric between two MWCNT/PEDOT:PSS composite electrodes. The fabricated flexible capacitive pressure sensor exhibited three different sensitivities of 1.12 MPa-1, 0.86 MPa-1 and 0.36 MPa-1; fast response time of 1 sec, a high stability over 10,000 compression-release cycle, and wide working pressure range of < 1200 kPa. For the real-time gait signal monitoring, we made a hole inside the insole and the fabricated pressure sensor was integrated into insole and put into the shoes. So, when the subject simply put on the shoes and walk, we can get the gait signal. And finally, through the simple capacitance to voltage converting circuit, composed of instrumentation amplifier, low pass filter, analog to digital converter and MATLAB signal processing, we have successfully demonstrated the real-time gait signal. Secondly, porous Ecoflex dielectric layer was made using sugar cube melting method and chopped carbon fiber was mixed with silver nanowires and deposited on top of the PDMS electrodes. After that, capacitive pressure sensor was completed by putting porous Ecoflex dielectric between two PDMS electrodes. The fabricated flexible pressure sensor exhibited a sensitivity of 0.155 kPa, a wide working pressure range of < 200 kPa, and a high durability over 6,000 cycles. For the real-time breathing signal monitoring, the fabricated pressure sensor was attached to the back side of the belt. When the subject just simply wore the belt and take a breath, we could get the breathing signal. Through capacitance to voltage converting circuit and MATLAB signal processing same as above, we have successfully demonstrated the real-time breathing signal.

Nickel-PDMS Based Soft Capacitive Pressure Sensor without Leakage Current

박진균 서울대학교 대학원 2019 국내석사

The pressure sensor, classified into capacitive, piezo-resistive, piezo-electric and optical type, is one of the most fundamental components to realize electronic skins (E-skins), which can mimic human neural system especially mechanoreceptors. Thanks to the high durability and sensitivity of capacitive pressure sensor, it is a promising candidate for pressure receptor of E-skins. Therefore, several methods designing such sensor have been developed. Among those designs, composite-based capacitive sensors that use conducting particles dispersed uniformly as fillers inside of their dielectric matrix are attractive one due to its relatively easier and faster fabrication. In that specific type of pressure sensors, the capacitance values sharply change around percolation threshold region. It gives the possibility of remarkably high sensitivity, but at the same time, the prevention of leakage current through both electrodes is mandatory. Although there have been reports showing high sensitivity near percolation threshold for conducting micro-particles composite based pressure sensors, the studies to prevent the leakage current near percolation threshold were often neglected in many researches. In this paper, we introduce a sensitive capacitive-type pressure sensor based on micro-sized nickel particles composite with successfully extirpating leakage current around percolation threshold. As a result, the pressure sensing range has increased enormously because our sensor does not show breakdown phenomenon even under a high pressure. By spin-coating a thin polydimethylsiloxane (PDMS) film onto inkjet-printed silver nanoparticles (AgNPs) electrode as the first layer of dielectric material, the leakage current flow is stopped. When it comes to the electrodes, embedded elastomeric nanowires (silver nanowires, AgNWs) were designed as a flexible top electrode by directly embedding into the nickel-PDMS composite. Through this architecture, we expect that the top electrode is not destroyed by the applied pressure, and furthermore, this technology can be used to produce any type of flexible pressure sensors and applications to E-skins. The fabricated sensor is electrically characterized through pressure testing and the thickness of layers. Our sensor (nickel volume fraction f=0.2) shows the highest sensitivity in the range of 0 kPa to 100 kPa and sensor characteristics in a wide area more than 800 kPa. It also shows complete zero DC leakage current even at 1000 kPa which is the maximum applied pressure.

The study of multi-functional tactile sensor for tactile recorder

Jeonggyun Jang DGIST 2024 국내석사

In the human tactile system, various receptors located in the skin to respond for external stimuli of touched objects. The most important external stimuli sensed by these tactile receptors are pressure and temperature. Therefore, many research have recently been conducted on tactile sensors that can detect temperature and pressure using various materials and principles by imitating the human tactile system. However, spatial detecting resolution is low due to material limitations or crude design. Tactile sensors with low spatial resolution cannot obtain detailed information, such as the roughness and shape of the object surface, like natural human skin (especially fingers with sensitive tactile senses). Additionally, most of sensor system design consist of two part, pressure sensing part and temperature sensing part separately. The design can induce complicated fabrication steps or poor system reliability. In this thesis, we suggested a tactile sensor designed with a unique structure in which the common electrode of the pressure sensor functions as a temperature sensor. This structure overcames the problems of previously studied tactile sensors, such as difficult processability and durability. The high-resolution multifunctional tactile sensor designed to measure temperature and pressure simultaneously. The tactile sensor consists of a resistive temperature sensor and a pressure sensor using piezoelectric material (PVDF-TrFE) to detect temperature and pressure, respectively. It also comprises 25 pressure-sensing cells of 1 mm2 for high spatial resolution. The process conditions for the temperature and pressure sensors were optimized to fabricate the tactile sensors. The piezoelectric voltage signal was increased by adjusting the thickness of the temperature sensor electrode. Additionally, the coating and annealing conditions of the PVDF-TrFE film of the pressure sensor were optimized to improve piezoelectric voltage signal generation. PVDF-TrFE was etched with RIE to eliminate crosstalk between pressure sensing cells, increasing sensor reliability. The fabricated tactile sensor accurately detected applied pressure and temperature with a short response time and linearity to temperature and pressure stimuli. Moreover, the sensing cell array can detect the area where an object touches the tactile sensor. Additionally, the surface roughness and the topography information of objects can be obtained with high spatial resolution. Because the zigzag arrangement design of the cells eliminates empty space when objects are pushed and detected. Due to the pyroelectric properties of PVDF-TrFE, the change in piezoelectric voltage signal depended on temperature of touching object was corrected by writing a correction equation using the result from temperature sensor. This equation allows the tactile sensor to detect temperature and pressure stimuli more accurately for various conditions. Tactile recording system was developed a tactile recording system using these tactile sensors, as well. Tactile recording system displays the signals obtained from tactile sensors in real time and automatically saves the data. The saved data can be used to analyze various information, of touching objects and to generate artificial tactile sensor using haptic actuators. 인간의 촉각 시스템은 피부 속에 위치한 다양한 수용체가 외부 자극에 반응하여 닿은 물체를 감지합니다. 이런 촉각 수용체가 가장 중요하게 감지하는 외부 자극은 압력과 온도입니다. 이런 인간의 촉각 시스템을 모방해 다양한 재료와 원리로 온도와 압력을 모두 감지할 수 있는 촉각센서에 대한 연구가 최근 많이 이루어지고 있다. 하지만 재료의 한계 또는 투박한 디자인으로 인해 낮은 공간 분해능을 가집니다. 공간 분해능이 낮은 촉각센서는 사람의 실제 피부(특히 촉각이 민감한 손가락)처럼 물체 표면의 거칠기, 형상과 같은 세밀한 정보를 얻을 수 없습니다. 이 논문에서는 온도와 압력을 동시에 측정하도록 설계된 높은 분해능을 가진 다기능 촉각 센서를 제시합니다. 촉각 센서는 저항성 온도 센서와 압전 물질(PVDF-TrFE)를 활용한 압력센서로 제작되어 온도와 압력을 감지합니다. 또한 높은 공간 분해능을 위해 1mm2의 압력 감지 셀 25개로 구성되어 있습니다. 이 촉각 센서는 압력센서의 공통 전극이 온도센서 역할을 수행하는 독특한 구조로 설계했습니다. 이 구조는 이전에 연구된 촉각 센서의 어려운 공정, 내구성과 같은 문제점들을 극복했습니다. 우리는 촉각센서를 제작하기 위해 온도와 압력센서 부분의 공정 조건을 최적화했습니다. 온도센서 전극의 두께를 조절해 압전전압 신호를 증가시켰습니다. 그리고 압력센서의 PVDF-TrFE 필름의 코팅과 어닐링 조건을 최적화해 압전전압 신호 발생을 향상시켰습니다. 또한 PVDF-TrFE를 RIE로 에칭해 압력 감지 셀 간의 크로스톡을 제거해 센서의 신뢰도를 높였습니다. 제작된 촉각센서는 온도와 압력 자극에 짧은 반응시간과 선형성을 가져 가해진 압력과 온도를 정확히 감지합니다. 그리고 촉각센서에 물체가 닿은 영역을 셀 어레이를 통해 감지할 수 있습니다. 또한 높은 공간 분해능으로 물체의 표면 거칠기와 지형정보를 얻을 수 있습니다. 왜냐하면 지그재그로 위치한 셀 어레이가 물체를 슬라이딩해 감지할 때 빈공간을 없애 주기 때문이다. PVDF-TrFE의 초전기 특성으로 인해 가열된 물체가 압력을 가할 때 발생하는 압전전압 신호의 변화를 교정식을 만들어 해결했습니다. 이를 통해 촉각센서는 온도와 압력 자극이 동시에 발생하는 상황에도 두 인자를 정확하게 감지합니다. 우리는 이런 촉각센서를 이용해 촉각 레코더 시스템을 개발했습니다. 촉각 레코더 시스템은 촉각센서로부터 얻은 신호를 실시간으로 보여줍니다. 또한 동일한 데이터를 자동으로 저장합니다. 저장된 데이터는 물체의 경도, 거칠기와 같은 다양한 정보를 분석하는데 활용될 수 있습니다.

Development of Electrospun Hybrid Nanofibrous Membrane based Flexible and Stretchable Physical Sensors for Wearable Bioelectronics

수딥 광운대학교 일반대학원 2023 국내박사

Recently, emerging studies about wearable bioelectronics have attracted substantial research interest because of their colossal multifunctional potential for application in intelligent robotics, flexible touch screens, smart electronic skin, physiological signal monitoring, and human−machine interface. Flexible and stretchable physical sensor with high sensitivity, linearity and durability is a critical requirement for the versatile application. There is an increasing need for wearable technology that can track important physiological signals like blood glucose levels, blood pressure, and heart rate, body temperature and hydration in real-time, due to the rising incidence of chronic illnesses including diabetes, heart disease, and hypertension. The objective of this thesis is to create a novel sensing platform that can be included into wearable technology and use to continuously monitor a variety of biometric factors, including pressure, strain, temperature, humidity, and ECG signals, as well as create algorithms for processing and analyzing the data produced by these devices. First, a dielectric-type capacitive pressure sensor by sandwiching a composite nanofibrous nanomesh as a dielectric layer between two PEDOT: PSS nanocomposite electrodes was developed. The composite nanomesh membrane was made by blending 2D material Ti3C2Tx (MXene) with PVDF polymer followed by electrospinning process. Owing to the porous and highly deformable morphology of the membrane, a small pressure can easily trigger a deformation, which induces the variation in dielectric properties of the nanomesh membrane and reduces the height of the two electrodes. Therefore, the change in dielectric properties and electrodes distance reflect the magnitude of the applied pressure. The fabricated sensor exhibited a sensitivity of 0.5 kPa-1 in linear range of 0.6 kPa. This sensor was capable of accurately detecting physiological signals in the low-to-medium pressure range. Second, an ionic-type EDL-capacitive pressure sensor by sandwiching hybrid ionic nanofibrous membrane between microstructured Au/PDMS electrodes was developed. The membrane was composed of PVA, LiTFSi, and MXene. The results of this study revealed that the functional layer (−OH, −F, and −O) on the MXene surface trapped ions [Li]+[TFSI]−) via H-bonds, which considerably decreased its initial capacitance (C0) by inhibiting the EDL formation at the electrode/electrolyte interface. The ion pumping process triggered by external stimuli generated a thick EDL at the interface, causing a significant capacitance change and ensuring high-pressure sensitivity of the device. The reversible ion pumping triggered by a hydrogen bond in the hybrid sensing layer leads to high sensitivities of 5.5 kPa-1 in linear range of 0-30 kPa. The study produced excellent results, and the sensor could pick up ultra-low vibration signals while at rest. Third, a piezoresistive material where PANI-nanospines were uniformly deposited on carbonized nanofibrous nanomesh membrane was developed. The engineered membrane was comprised of PAN, cellulose, and MXene, in which MXene and cellulose were used as reinforcing agents in PAN nanofiber. The presence of PANI-nanospines on the nanofibers created a larger area of roughness and higher difference in contact area which increase the pressure sensitivity to 179.1 kPa-1 across a linear range of 0-50 kPa. The fabricated sensor enabled for subtle detection (wrist pulse, heart rate, JVP) despite significant body deformations (e.g., running, jumping, exercise, etc.). Fourth, a flexible and stretchable supercapacitive pressure sensor was developed. The key innovation in the proposed sensor design was the use of graphene nanocomposite electrolyte (GNE), which was made of polyaniline-modified 3D-nanoporous carbon-incorporated laser-engraved graphene as an electrode material and depositing an IL-blended P(vdf-HFP) polymer electrolyte mixture directly onto the electrode to utilize the large surface area of the electrode. Additionally, the low-ion-concentration nanofibrous nanomesh was sandwiched between the GNE films, which offers a high degree of compressibility and also had an important role in tuning the EDL at the electrode/electrolyte interface. The synergistic effect of the high-surface-area electrode and the highly compressible membrane was leveraged to reduce C0 and increase Cp under pressure, resulting in ultra-high sensitivity and wide linearity (9029 kPa−1 up to 100 kPa). The fabricated sensor was utilized for continuous posture monitoring and rehabilitation propose. Fifth, an all-directional strain-insensitive stretchable e-glove capable of simultaneously detecting and differentiating ECG, temperature, humidity, and pressure stimuli in real time was developed. Considering the facile, low-cost, and scalable manufacturing of stretchable e-gloves that are crucial for extensive applications, a promising fabrication technique utilizing CO2 laser engraving was explored. The highly sensitive CNT/LEG was used as an active sensing material to form ripple-like meandering interconnections and sensing areas for all the sensors on a styrene-ethylene-butylene-styrene (SEBS) elastomer. Additionally, the meandering structure was designed with five ripple-like strata superimposed in four directions at an inward-facing loop providing an all-directional strain-insensitive structure. Importantly, the structure was tailored to stretch in accordance with the mechanical movements of the hand, offering a high degree of spatiotemporal sensitivity and significantly boosting perception across all directional mechanical stimuli. A simple lamination process was used to judiciously integrate four independent functional sensors on a SEBS elastomer in layer-by-layer geometry to reduce the overall sensor footprint. The performance of the fabricated sensors was validated against a gold-standard assay, and the crosstalk of the sensors from various stimuli was evaluated. To minimize crosstalk between temperature and pressure, the transducing principle was performed differently, while for temperature and humidity, the temperature sensor was entirely encapsulated, and the area of the humidity sensor was kept to a minimum.

Development of a Multi-Array Pressure Sensor Module for Non-invasive Blood Pressure Measurement on Radial Artery

노동근 전남대학교 대학원 2020 국내석사

Increased interest in blood pressure management requires more convenient measurement technology for monitoring blood pressure throughout the day. Measuring blood pressure from radial artery pulsations is a popular approach, but it is not yet possible to accurately estimate blood pressure. One of the reasons is that it is difficult to properly place the pressure measurement sensor over the radial artery hidden in the skin. To solve this, multi-channel pressure sensors having a lattice-type structure have been proposed, but the optimized structure has not been verified yet. The objectives of this study is to develop a multi-array pressure sensor module that has novel staggered grid structure of sensor unit to effectively measure the pulsation pressure on the radial artery and is to verify the feasibility of the developed sensor module in measuring blood pressure. Proposed multi-array pressure sensor module has 17.6 × 17.6 mm2 area and consists of seven pressure sensor units arranged in hexagonal structure with midpoint and covered with polydimethylsiloxane. Rear side of proposed sensor module embeds analog-front-end for signal amplification. For characteristic evaluation of developed sensor module, computer simulation and actual pressure test using push-pull gauge were carried out, and both results commonly confirmed that the developed sensor module reacts linearly to external pressure. However, in the push-pull gauge test results, it was found that the pressure attenuation and inter-channel difference that may be stemmed on the deviation of each sensor unit or manufacturing process of sensor module. Therefore, the calibration equations were derived channel by channel to compensate the pressure and minimize the inter-channel difference. As a result of the calibration, the root mean square error of the pressure response of a sensor module was 0.267 kPa. For investigating the feasibility of developed sensor module in monitoring blood pressure, radial artery pulse wave measured by developed sensor module and non-invasively measured continuous blood pressure were obtained from 10 young and healthy participants (8 males, 2 females, 23.6 ± 2.1 years, systolic blood pressure : 120.3 ± 7.4 mmHg, diastolic blood pressure : 78.7 ± 8.9 mmHg) and evaluated by correlation analysis and regression analysis with systolic and diastolic blood pressure. All analysis were performed on systolic and diastolic blood pressure values ​​of continuous blood pressure, and systolic and diastolic features of pulse wave such as maxima or minima of pulsatile waveform. As a result, the average correlation coefficient excluding the abnormal data has a value of 0.841 ± 0.105 (mean ± SD), coefficient of determination of the systolic and diastolic blood pressure estimation models are 0.35 ± 0.38 and 0.37 ± 0.34, respectively, and the root mean square error of regression model has values ​​of 5.97 ± 3.45 mmHg and 2.26 ± 1.24 mmHg for systolic and diastolic blood pressure, respectively. These results suggest that the waveform obtained by newly developed multi-array pressure sensor module has strong correlation with continuous blood pressure waveform. Though measuring the blood pressure using developed sensor module has large inter-subject difference and requires customized calibration procedure, it shows the possibility of use through further studies. I believe that the pressure sensor developed in this study could be used to estimate blood pressure in the future, and should be applicable to health monitoring for diagnosis and prevention of cardiovascular diseases. 혈압 관리에 대한 관심이 증가함에 따라 하루 종일 혈압을 모니터링하기 위해 보다 편리한 측정 기술이 요구된다. 요골 동맥 맥파를 통해 혈압을 측정하는 것은 대중적인 방법이지만 정확히 혈압을 추정 할 수 없다. 이유 중 하나는 압력 센서를 피부 아래에 숨겨져 있는 요골 동맥 위에 제대로 위치시키기 어렵기 때문이다. 이를 해결하기 위해 격자형 구조를 갖는 다채널 압력 센서가 제안되었지만 최적화된 구조는 아직 검증되지 않았다. 이 연구의 목표는 요골 동맥의 맥동 압력을 효과적으로 측정하고 혈압 측정에서 개발된 센서 모듈의 타당성을 검증하기 위해 단일 센서가 엇갈린 격자 구조를 갖는 다중 배열 압력 센서 모듈을 개발하는 것이다. 제안된 다중 배열 압력 센서 모듈은 17.6 × 17.6 mm2 면적을 가지며 중앙에 센서를 가진 육각형 구조로 배열되고, 폴리디메틸실록산으로 덮인 7개의 개별 압력 센서로 구성된다. 제안된 센서 모듈의 후면에는 신호 증폭을 위한 아날로그-프론트-엔드가 내장되어 있다. 개발된 센서 모듈의 특성 평가를 위해 푸시-풀 게이지를 사용한 컴퓨터 시뮬레이션 및 실제 압력 테스트가 수행되었으며, 두 결과 모두 개발된 센서 모듈이 외부 압력에 선형으로 반응함을 확인했다. 그러나, 푸시-풀 게이지 테스트 결과에서, 구성되는 개별 센서의 편차와 센서 모듈의 제조 공정으로 인한 압력 감쇠 및 채널 간 차이가 발견되었다. 따라서, 보정 방정식은 압력을 보상하고 채널 간 차이를 최소화하기 위해 채널별로 도출되었다. 보정 결과, 센서 모듈의 압력 응답의 평균 제곱근 오차는 0.267 kPa 이다. 혈압 모니터링에 있어서 개발된 센서 모듈의 타당성을 조사하기 위해 개발된 센서 모듈을 이용하여 측정된 요골 동맥 맥파와 비 침습적으로 측정된 연속 혈압을 10명의 젊고 건강한 참가자 (8명의 남성, 2명의 여성, 23.6 ± 2.1년, 수축기 혈압 : 120.3 ± 7.4 mmHg, 이완기 혈압 : 78.7 ± 8.9 mmHg)로부터 얻었으며, 수축기 및 이완기 혈압과의 상관 분석과 회귀 분석에 의해 평가되었다. 모든 분석은 연속 혈압의 수축기 및 이완기 혈압 값과 맥동의 수축기 및 이완기 특징, 예를 들어 맥동 또는 최소 맥동 파형에 대해 수행되었다. 결과적으로, 비정상 데이터를 제외한 평균 상관 계수는 0.841 ± 0.105(평균 ± 표준편차)의 값을 가지며, 수축기 및 이완기 혈압 추정 모델의 결정 계수는 각각 0.35 ± 0.38 및 0.37 ± 0.34 이고, 회귀 모델의 평균 제곱근 오차는 각각 수축기 및 이완기 혈압에 대해 5.97 ± 3.45 mmHg 및 2.26 ± 1.24 mmHg의 값을 가진다. 이러한 결과는 새롭게 개발된 다중 배열 압력 센서 모듈에서 얻은 파형이 연속 혈압 파형과 강한 상관관계를 가지고 있음을 시사한다. 개발된 센서 모듈을 이용하여 혈압 측정 시 측정자 간 차이가 크고 개인 맞춤형 교정 절차가 필요하지만 추가 연구를 통해 혈압 추정을 할 수 있는 가능성을 보여준다. 본 연구에서 개발한 압력센서가 향후 혈압을 추정하는 데 사용될 수 있으며, 심혈관 질환의 진단 및 예방을 위한 건강 모니터링에 적용될 수 있다.

Artificial Tactile System and Signal Processing for Haptic applications

Minkyung Sim DGIST 2021 국내박사

Human have the ability to interact with the external environment through five main senses which are vision, hearing, smell, taste and touch. Most of all, the sensation like vision or hearing have been well developed and the use of various applications like TV, Camera, or artificial cochlear have been widely generalized. As the next steps, recently, the tactile sensor to mimic the tactile system of human have been attracted by many groups. Especially, after the development of Apple’s iPhone, the public interest about touch sensing applications have been increased explosively. Other researches for tactile sensing have focused on enhancing the performance of tactile sensor like the sensitivity, stability, response time and so on. As a result, there are some researches that the sensor performance of certain criteria is better than that of human tactile system. However, a human tactile system is not only very sensitive but also complex. In other words, ultimately, the tactile system mimicking the human tactile sensation should detect various parameters such as the pressure, temperature, hardness or roughness and also decide the psychological feeling like the pain by a hot material in touching or the smooth/roughness feeling in sliding the certain material. Therefore, in this thesis, it has been studied for the development of multifunctional tactile sensing system detecting various tactile parameters and deciding the kinds of psychological tactile feeling by measured stimulation. As the first step for the development of tactile system, we have studied the tactile sensor using ZnO nanowire. Therefore, in this chapter, the basic characteristics of ZnO nanowire are investigated to confirm the possibility for the tactile sensor. In addition, structural design factors of sensor units have been studied in order to enhance the sensitivity of ZnO nanowire-based tactile sensor. We have primarily demonstrated the effect of a square pattern array design in a pressure sensor using ZnO nanowires. Nanowires grown on the edge of cells can be bent easily because of growth direction, density of nanowires, and buckling effect. Since smaller square pattern arrays induce a higher circumference to cell area ratio, if one sensor unit consists of many micro-level square pattern arrays, the design enhances the piezoelectric efficiency and the sensitivity. As a result, 20um × 20um cell arrays showed three times higher pressure sensitivity than 250um × 250um cell array structures at a pressure range from 4kPa to 14kPa. The induced piezoelectric voltage with the same pressure level also increased drastically. Therefore, the smaller pattern array design is more appropriate for a high-sensitive pressure sensor than a simple one-body cell design for tactile systems, and it has the advantage of better power efficiency, which is also important for artificial tactile systems. Even if, in previous experiments, the possibility of piezoelectric materials as the tactile sensor and the method for the enhancement of pressure sensitivity are confirmed well, the tactile sensor for mimicking the human tactile sensation should measure various parameters as well as the pressure. However, many studies about ‘smooth-rough’ sensation depend on the machine learning technology with simple tactile sensors rather than developing the sensors that can measure various parameters like surface topography, hardness, quality of materials at the same time. Therefore, after the development of the pressure sensor, specific structures based on PDMS are proposed to measure and analyze above-mentioned parameters related to ‘smooth-rough’ decision, as like fingerprint of human. To find the optimized structure, three kinds of the structure shape (cone, cylinder and dome) are fabricated and the pressure sensitivity according to the shape are also measured. FEM simulation is also carried out to support the experimental result. Our tactile sensor with optimized dome structure (500um height) provides high shear force sensitivity, fast response time, stability, and durability. The high sensitivity about the shear force enables better the tactile sensor to measure the various surface information such as the pitch of pattern, the depth, the sliding velocity, the hardness and so on. In addition, after the study to measure the various surface information by dome structure, the research to measure the other surface information is also followed. In our previous study, we confirmed that the surface topography can be reconstructed by mapping the piezoelectric signals according to the location. In this research, to reduce the number of measurements from dozens to once and minimize the data loss at the empty space between adjacent sensors, the electrode array of Zig-Zag type is applied to the tactile sensor. As a result, with just one measurement, the surface topography of broad region can be successfully reconstructed by our tactile sensor as the high-resolution image. Additionally, the temperature sensor based on the resistive mechanism is fabricated between the Zig-Zag electrode lines to measures the temperature of surface materials when the tactile sensor rubs on the materials in real time. Over the development of the tactile sensing applications, the demand for an artificial system like human tactile sensation have been much more increased. Therefore, in this study, as a surrogate for human tactile sensation, we propose an artificial tactile sensing system based on the developed sensors in previous sections. For this, the piezoelectric tactile signal generated by touching and rubbing the material is transferred to DAQ system connected with our tactile sensor. First, the system decides whether the contacted material is dangerous or not. If dangerous like sharp or hot materials, the warning signal is generated by our artificial tactile system. If not, the sensor connected with the system rubs the materials and detects the roughness of the materials. Especially, the human test data related to ‘soft-rough’ detection is applied to a deep learning structure allowing personalization of the system, because tactile responses vary among humans. This approach could be applied to electronic devices with tactile emotional exchange capabilities, as well as various advanced digital experiences. In this thesis, human-like tactile sensing system based on the piezoelectric effect is successfully confirmed through various experiments. Although there are still some issues that need to be improved, this research is expected to be fundamental results for human-like tactile sensing system detecting a variety of the parameters such as the pressure, temperature, surface morphology, hardness, roughness and so on. In the future, through collaborative research with other fields like brain science, signal processing, we hope that this research can mimic psychological tactile sensations and communicate emotional exchange with external environment like real human skin.

투명하고 유연한 압력센서를 이용한 촉각 보조 시스템 연구

김영성 고려대학교 대학원 2012 국내박사

[배경 및 목적] 인간은 오감-시각, 청각, 후각, 미각, 촉각-을 통하여 정보를 얻고 주변 환경과 상호 작용한다. 만약 인간에게 이런 감각을 느끼게 해주는 감각기관이 없다면 인간은 생존 자체를 위협받을 것이고, 인간의 삶을 영위하는데 많은 어려움을 줄 것이다. 특히 최근의 많은 연구그룹들이 촉각에 대한 관심과 연구를 하는 이유는, 인간과 컴퓨터를 비롯한 기계와의 인터페이스가 촉각에 의해서 발생하기 때문이다. 인간은 눈으로 수많은 정보를 인지하기도 하지만, 촉각을 통해 얻을 수 있는 정보를 이용하여 손 또는 손가락을 사용한다. 인간의 촉각에 필적한 센서를 만들 수 있다면 기계와의 수많은 인터페이스를 간단하게 또는 편리하게 만들 수 있을 것이다. 하지만 아직 인간의 촉각과 같은 성능을 구현하지 못하고 있는데, 이상적인 촉각센서는 압력, 온도 등의 물리적인 양을 측정할 수 있는 고성능의 센서가 높은 고해상도를 갖도록 분포되어 있어야 한다. 동시에 유연성과 신축성을 가지고 있어서 인간의 피부와 같은 곡면에도 깨끗하게 부착되어 있어야 한다. 본 연구에서는 기존의 연구들이 성공하지 못했던 촉각센서를 구현하는 것을 목적으로 하여, 다음과 같은 해결 가능한 가설을 제시하고자 한다. 만일 투명하면서도 유연한 압력센서 어레이를 만들 수 있다면 기존의 불투명하고 뻣뻣한 재질을 가진 기존 촉각센서의 한계를 넘어서 굴곡이 심한 표면에 가해지는 압력까지 측정할 수 있을 것이다. 결론적으로 본 연구의 목적은 촉각센서를 구현하기 위해 서로 다른 압력을 인지함과 동시에 피부에 부착할 수 있는 유연하고 투명한 압력센서 어레이를 만드는 것이 목적이다. [연구방법] 본 연구에서는 서로 다른 압력을 인지할 수 있고, 동시에 유연하면서도 투명한 압력센서 어레이를 구현하기 위하여 광도파로를 이용한 광학압력센서를 구현하고자 한다. 우선 광학압력센서의 구조는 바깥쪽을 둘러싼 2개의 클래딩층과 1개의 코어층으로 된 3중 구조로 이룬다. 이것은 상단과 하단의 클래딩층이 가운데에 위치한 코어층을 둘러싸고 있는 구조다. 여기서 상단의 클래딩층에서 손가락이 닿는 부위, 즉 센싱하는 특정부위는 공기와 직접 닿도록 개방되어 있다. 이러한 센싱부위를 3ⅹ3 어레이(Array)로 구현하여 서로 다른 압력을 인지하도록 한다. 또한 제안하는 촉각센서가 유연하고 투명한 특성을 가지기 위해서 자체적으로 프리폴리머를 합성하여 사용한다. 합성한 프리폴리머의 특성을 필름타입으로 제작하여 확인하고, 프로토타입의 압력센서 어레이를 만든 후 센서의 성능을 검증한다. 성능을 확인하는 목적은 두 가지로, 첫 번째는 압력센서로써의 성능을 검증하는 것이고, 두 번째는 압력센서를 피부에 부착하여 유연성과 투명성을 확인하는 것이다. [연구결과] 본 연구에서 구현한 어레이 센서에 가해진 압력에 따라 광도파로의 광량이 변하는 것을 이용하여 센싱 부위에 가해진 압력에 따른 분포도를 나타내는 압력분포지도를 재구성할 수 있는 성능을 보여주고 있다. 또한 합성으로 제작한 폴리머 재료의 유연한 특성을 확인한 결과 75?의 최대각도를 보여주고 있다. 이때의 입출력 대비 광량의 손실도는 6% 미만이다. 이러한 유연한 특성을 살려서 3ⅹ3의 어레이 센서를 구현하였고, 인간의 피부에 접착하여 시각적인 투명도가 95%이상임을 확인하였다. 센서로써의 성능을 검증하는 실험에서 보여주는 결과는 가해지는 압력에 따라 광량이 분명히 감소하는 경향과 함께, 실험결과로 0~15dB의 압력을 측정할 수 있는 성능을 보이고 있다. [결론] 본 연구에서 구현한 센서는 기존의 압력센서들이 가지지 못한 유연성과 투명성을 구현한 압력센서 어레이다. 이 센서는 서로 다른 압력이 가해지는 센싱 부위의 압력을 측정할 수 있고, 그 투명도가 매우 우수하여 인체에 부착 시 사용자가 거부감을 가지지 않는 부착성을 보이고 있다. 그렇기 때문에 단순한 압력센서로 사용하는 산업분야뿐만 아니라 로보틱스, 메디컬 분야 등 다양한 응용분야에 적용이 가능할 것으로 보인다. 또한 IT 분야의 사용자 인터페이스에 사용한다면 인간에게 보다 편리한 기능을 제공하는 센서가 될 것으로 기대된다. [Background and Purpose] Human uses 5 senses- sight, hearing, smell, taste and touch- to get the information interact with surrounding environment. Without such sense organs to human must become a threat to human survival. The reason that there is becoming a lot of interest in tactile many haptic researches are in progress is that the interface between humans and machines including computers is caused by tactile. For example, all IT equipment that human use and devices used in the medical field are used by hands and eyes. Human sees and recognizes a great number of information through the eyes, judges by using head and controls by hand. Especially, tactile is very important sense when controlling by hand. If tactile sensor comparable with human touch sense would be made, many interfaces with devices could become simple and convenient. But unfortunately there are no tactile sensors comparable with human sense. Ideal tactile sensor should be distributed to have a high resolution performance that can make sensor measure pressure, temperature and physical quantities. Also it should have flexibility and elasticity in order to adhere to curved surfaces such as human skin. The purpose of this paper is to realize tactile sensor that earlier studies failed to make. So this paper gives the hypothesis as follows ? if this study is able to make transparent and flexible pressure sensor, it can make overcome limitations of conventional tactile sensors made with opaque and stiff material and also measure the pressure given on curved surfaces. Therefore the purpose of this study is to make tactile sensor array with flexibility and transparency in order to attach to skin. [Methods] This paper uses optical pressure sensor using by optical waveguide to make flexible and transparent tactile sensor array. The tactile sensor consists of 3 layers ? 2 cladding layers and one core layer. The core layer is surrounded with the upper and bottom cladding layer. The specific sensing part of the upper cladding layer is the finger touching part and open to contact with air directly. The sensing area to be able to make the array can be used as a tactile sensor. In addition, the proposed tactile sensor in order to have a flexible and transparent nature uses prepolymer that this study synthesized itself. For this, there are two steps to verify after making the array of prototype tactile sensor. The first step is to verify performance as a tactile sensor and the second is to investigate the performance when attached to skin. [Results] The proposed tactile sensor shows the performance to reconstruct pressure distribution map which displays distribution according to pressure given on specific areas. It uses change of light of optical waveguide depending on the intensity of the pressure exerted on the sensor. Also the sensor represents the good performance as flexible tactile sensor that attaches to human skin. The result of last validated test shows tendency to decrease light intensity depending on pressure. As a result of the test, this sensor can measure the pressure 0~15dB and also present the function of the sensor when attaching to skin. [Conclusion] The tactile sensor of this paper is a sensor with flexibility and transparency that existing sensors did not have. The excellent transparency of the sensor when a user wearing on the body without rejection can seem to be applied various applications. in addition to medical field as well as other areas, if it would be used as the user interface, it is expected to provide to humans convenience as sensor in addition to medical field as well as other areas.