複数の静電容量型柔軟触覚デバイスを用いた三軸力センサの開発

早大学位記番号:新7325早稲田大

Advanced sensors technology survey

This project assesses the state-of-the-art in advanced or 'smart' sensors technology for NASA Life Sciences research applications with an emphasis on those sensors with potential applications on the space station freedom (SSF). The objectives are: (1) to conduct literature reviews on relevant advanced sensor technology; (2) to interview various scientists and engineers in industry, academia, and government who are knowledgeable on this topic; (3) to provide viewpoints and opinions regarding the potential applications of this technology on the SSF; and (4) to provide summary charts of relevant technologies and centers where these technologies are being developed

Development of a pressure sensor network system for static and dynamic pressure measurements: application to the limb/prosthesis pressure mapping

Tese de doutoramento em Ciências - FísicaThe present work relates to the development of a sensors network for mapping the pressure fields at the externa! prosthesis socket/stump interface, in particular at lower limbs. The project consists on the design and implementation of a sensor array from piezoresistive polymer based materiais to measure quasi-static and dynamic deformations. The sensors were prepared from poly(vinylidene fluoride) - PVDF and epoxy nanocomposites with carbon nanotubes or nanofibres. The development of thin film-based stretchable electrodes was carried out using the GLancing Angle Deposition, GLAD, technique. A specific electronic circuit for signal processing was used with a wireless data acquisition system. Finally, a prototype was designed , constructed and tested in four IO\.ver limb amputees, in laboratory conditions , under different types of solicitations at the Vocational Rehabilitation Center - CRPG (Centro de Reabilitação Profissional de Vila Nova de Gaia). The piezoresistive-based sensors were developed using two different approaches; a) nanocomposites composed of poly(vinylidene~ fluoride) filled with carbon nanotubes (CNT/PVDF); and b) epoxy resins filled with carbon nanotubes or nanofibres (CNT/EPOXY). The PVDF samples were prepared by hot pressing and spray printing with CNT sample concentrations up to loadings of 1 O wt.%. The phase present in the composites CNT/PVDF was the alfa-phase. Due to the fact that externa! limb prostheses must sustain cyclic loading and unloading during normal walking conditions, the correlation between the electrical resisitivity and mechanical solicitations was obtained for differents mechanical solicitations, including variations in deformation , temperature and velocity. ln relation to CNT/EPOXY, the electrical response is linear over a wide strain range and the values of the maximum gauge factor is ~2 . 8 . The stability of the signal over 32 cycles, the time response to deformatoins from 0.1 to 50 mm min- 1 and the stable temperature behaviour up to 60 °C shows the viability of these materiais to be used as piezoresistive sensors. ln the sarne way, the electrical and piezoresistive response of CNT/PVDF composites has been studied. The piezoresistive response, quantitatively analysed by the gauge factor, is maximized at concentrations around the percolation threshold, around 2 wt.% loading, and the maximum value of the gauge factor is ~6.2. The piezoresistive response is stable with the number of cycles and reversible up to temperatures below 100 °C. The linearity of the response over a wide strain range shows the viability of these materiais to be used as piezoresistive sensors. The development of stretchable electrodes was carried out using columnar Ti-Ag thin films with a Ag content of 8 at.% prepared by D.C. magnetron sputtering on CNT/PVDF piezoresistive composites. The Ti-Ag system was chosen to coat the polymers due to some important points related to its characteristics. First of ali, Ti-Ag thin films combine the excellent biocompatibility of Ti with the Ag antimicrobial properties, offering also good thermal, electrical , chemical and mechanical properties, together with good wear and corrosion resistance. Secondly, the addition of Ag was also thought in order to tailor the elasticity of the Ti films, allowing a better response of the coated polymer under any particular deformation or stretching of the composite sensor when in-service. Additionally, the deposition of the films by GLancing Angel Deposition , GLAD, instead of conventional Magnetron Sputtering Deposition , MSD, was also carried to allow and even extend this elasticity resistance. ln fact, by depositing films with some particular architectures , inclined, zigzag, etc., there is a real possibility to deposit thin films with extended capacities to resist to stretching or any common deformation that a polymeric-based sensor induce when in-service. Furthermore, there is also the possibility to improve the electrical response of the system and this, ali together, to improve the response and the adequacy of the ali sensor arrangement in this particular type of applications . By changing the typical columnar growth microstructure, obtained by conventional sputtering, the goal was to tune the mechanical and electrical responses of the materiais. Upon uniaxial stretching of the prepared zigzag thin films, the resistance of the thin film starts increasing smoothly for strains up to 3%. Above 10% strain a sharp increase of the electrical resistance is observed due to film mechanical failure and therefore interruption of the electrical conductivity pathways. The best results were obtained when the polymer was coated with intermediate incident angles (a = 60°). The results show that the electrodes structure has a pronounced influence on the overall sensor response leading to values of the GF up to 85 mainly due to the electromechanical contribution of the thin film, which stability has to be studied for potential use for sensor applications itself. Human study was conducted at the Vocational Rehabilitation Center- CRPG (Centro de Reabilitação Profissional de Vila Nova de Gaia). The subjects transfemoral (TF) and transtibial (TI) amputees , walked for 2 minutes in a crosswalk at a relatively comfortable speed of 0.33 m/s. During this time it was possible to simulate a normal walk of approximately 40 m and the results provided good indications that it is possible to identify areas of criticai pressure. Thus, it is expected that the present method will become helpful for comprehensively evaluating the biomechanical conditions of the residual limb and prosthesis interface. The system developed in this project may allow monitoring of the process of rehabilitation with a new prosthesis and will support clinical decisions in relation to the potential effects of modifications on the socket, when adjustments are required.O presente trabalho descreve o desenvolvimento de uma matriz de sensores para mapear as pressão exercidas em próteses externas dos membros inferiores, na interface coto/prótese, baseados em materiais piezoresistivos para medir as deformações dinâmicas e quasi-estáticas . Os sensores foram preparados a partir de nanocompósitos de poli(fluoreto de vinilideno) - PVDF e resinas epoxy com nanotubos- CNT ou nanofibras- CNF de carbono. Adicionalmente, foram desenvolvidos elétrodos estiráveis baseados em filmes finos através da técnica de pulverização catódica GLAD, Glancing Angle Deposition. O circuito electrónico usado para o processamento de sinal foi desenvolvido com um sistema de aquisição de dados sem fios. Finalmente, foi construído um protótipo que foi testado em quatro pacientes amputados dos membros inferiores em condições de laboratório, sob diferentes tipos de solicitações no centro de reabilitação vocacional - CRPG (Centro de Reabilitação Profissional de Vila Nova de Gaia). Com base no efeito piezoresistivo , os sensores foram obtidos usando duas diferentes ... abordagens; a) compósitos de poli(fluoreto de vinilideno) com nanotubos de carbono (CNT/PVDF); e b) compósitos de resinas epóxi com nanotubos de carbono ou nanofibras (CNT/epóxi). As amostras de PVDF foram preparadas por prensagem a quente e/ou por spray com concentrações de CNT até 10 % em peso. A fase cristalina presente nos compósitos CNT/PVDF foi a fase alfa-PVDF. Foi obtida a correlação entre a resistividade elétrica e as diferentes solicitações mecânicas, através da deformação , da variação da temperatura, da velocidade e do tempo de resposta do compósito. Em relação aos compósitos de CNT/epóxi, obteve-se uma resposta elétrica linear e os valores de sensibilidade máxima (gauge factor) foram de ~ 2.8. Através das diferentes solicitações mecânicas , a estabilidade do sinal para mais de 32 ciclos, o tempo de resposta para deformações de 0.1 a 50 mm min· 1 e a estabilidade com a temperatura até 60 oc mostram a viabilidade destes materiais para serem utilizados como sensores piezoresistivos. Da mesma forma , a resposta elétrica e piezoresistiva dos compósitos de CNT/PVDF foi estudada. A resposta piezoresisitiva foi quantitativamente analisada pela sensibilidade do material (gauge factor) e verificou-se que é máxima para concentrações em tomo do limiar de percolação, ~2 % de CNT em peso, e o valor máximo obtido foi de ~ 6.2. A resposta piezoresistiva é estável em função do número de ciclos e reversível até temperaturas inferiores a 100 °C. A linearidade da resposta com a deformação mostra a viabilidade destes materiais para serem utilizados como sensores piezoresistivos. O desenvolvimento de elétrodos estiráveis foi realizado usando filmes finos com estrutura colunar de titânio e prata - Ti-Ag com um teor de Ag de 8 at.% preparados por pulverização catódica em compósitos piezoresistivos de CNT/PVDF. O sistema Ti-Ag foi escolhido para revestir os polímeros devido a alguns pontos importantes relacionados com as suas características. Primeiro de tudo , filmes finos de Ti-Ag combinam a excelente biocompatibilidade do titânio com as propriedades anti-microbianas da prata, oferecendo deste modo boas propriedades químicas, mecânicas e elétricas, juntamente com boas propriedades de resistência ao desgaste e corrosão. Segundo, a adição de prata também foi incluída com o objetivo de promover a elasticidade do filme de modo a permitir uma melhor adaptação do filme ao polímero. Por outro lado, o sistema GLAD teve por grande objetivo este mesmo propósito: melhorar a resposta elétrica e a elasticidade do sistema de modo a permitir uma melhor adequação à deposição dos elétrodos em materiais flexíveis. A técnica de GLAD foi usada para alterar a microestrutura típica de crescimento colunar obtida por pulverização catódica convencional , Magnetron Sputtering Deposition, MSD, em diferentes arquiteturas de crescimento , tais como colunas inclinadas e em ziguezague, a fim de ajustar as respostas meéânicas e elétricas dos materiais. Após estiramento uniaxial dos filmes finos em ziguezague, a resistência eléctrica do filme fino começa a aumentar tenuemente para tensões até 3%. Acima de 10% de estiramento dá-se um aumento acentuado da resistência eléctrica que é observado devido à falha mecânica do filme . Os melhores resultados foram obtidos quando o polímero foi revestido com filmes depositados com ângulos incidentes intermédios (a = 60 °). Os resultados mostram que a estrutura dos elétrodos tem uma acentuada influência sobre a resposta global do sensor levando a valores de sensibilidade até 85. Esta contribuição deve-se essencialmente à contribuição eletromecânica do filme fino. O estudo com Pacientes foi realizado no centro de reabilitação profissional- CRPG (Centro de Reabilitação Profissional de Gaia), com amputados transfemoral (TF) e amputados transtibial (TT), que caminharam durante 2 minutos numa passadeira eléctrica com uma velocidade relativamente confortável de 0,33 rn/s. Durante este tempo , foi possível simular uma marcha normal de aproximadamente 40m. Deste modo demonstrou-se que é possível identificar as áreas criticas de pressão. Espera-se que, o presente método, se tome útil para avaliar exaustivamente as interações biomecânicas entre o membro amputado e a prótese. O sistema desenvolvido neste projeto poderá permitir o monitoramento durante o processo de reabilitação e apoiar em decisões clínicas em relação aos potenciais efeitos e modificações do encaixe da prótese no coto .Fundação para a Ciência e a Tecnologia (FCT) for the financial support (SFRH/BD/69796/2010)

Development of dynamic pressure sensor for high temperature applications

Pressure measurement under high temperature environments is required in many engineering applications and it poses many practical problems. Pressure patterns are highly desirable for health monitoring for improved performance and accurate prediction of remaining life of systems used in various applications. Data acquisition in harsh environments has always been a major challenge to the available technology. Sensing becomes more intricate in case if it has to operate under extreme conditions of temperature. Propulsion system applications represent one such area that requires a sensor that is absolutely accurate and has utmost sensitivity coupled with the ability to withstand high temperature. The need for such sensors is driven by the dependence of the performance of propulsion system on pressure pattern encountered along the gas path. Associated with that, high resolution, small size, low time dependent drift and stable range of measurement will complete the performance of such Microsystems Sensors using the current technology are capable of reliable measurement for a limited time at an extremely high cost and are bulky thereby preventing online monitoring. Improvement in the durability of the sensors requires new technology and will definitely open new areas of research. A number of technologies have been lately investigated, these technologies targeting specific applications and they are limited by the maximum operating temperature. The objective of this research is to develop a dynamic pressure measurement system that would be capable of operating at high temperatures with the technology of the device based on Silicon Carbon Nitride (SiCN). The principle of operation is based on the drag effect. Silicon carbon-nitride (SiCN) is a material that has been little explored. The service temperature of SiCN is in the range of 1400°C. The structure is produced from a liquid polymer precursor that could be originally formed into any shape. The proposed micro sensor can measure dynamic pressure and detects flow which is very important to know as the flow continuity is critical in many applications. Furthermore pressure measurement can be used as a base for many aspects. For example the proposed micro sensor could be designed and packaged to be fitted in the gas turbine engine. The correlation of the acquired data from the sensors may provide valuable timely information on imminent instability in the gas flow, detect leakage, improve efficiency et

MEMS Accelerometers

Micro-electro-mechanical system (MEMS) devices are widely used for inertia, pressure, and ultrasound sensing applications. Research on integrated MEMS technology has undergone extensive development driven by the requirements of a compact footprint, low cost, and increased functionality. Accelerometers are among the most widely used sensors implemented in MEMS technology. MEMS accelerometers are showing a growing presence in almost all industries ranging from automotive to medical. A traditional MEMS accelerometer employs a proof mass suspended to springs, which displaces in response to an external acceleration. A single proof mass can be used for one- or multi-axis sensing. A variety of transduction mechanisms have been used to detect the displacement. They include capacitive, piezoelectric, thermal, tunneling, and optical mechanisms. Capacitive accelerometers are widely used due to their DC measurement interface, thermal stability, reliability, and low cost. However, they are sensitive to electromagnetic field interferences and have poor performance for high-end applications (e.g., precise attitude control for the satellite). Over the past three decades, steady progress has been made in the area of optical accelerometers for high-performance and high-sensitivity applications but several challenges are still to be tackled by researchers and engineers to fully realize opto-mechanical accelerometers, such as chip-scale integration, scaling, low bandwidth, etc

New generation of interactive platforms based on novel printed smart materials

Programa doutoral em Engenharia Eletrónica e de Computadores (área de Instrumentação e Microssistemas Eletrónicos)The last decade was marked by the computer-paradigm changing with other digital devices suddenly becoming available to the general public, such as tablets and smartphones. A shift in perspective from computer to materials as the centerpiece of digital interaction is leading to a diversification of interaction contexts, objects and applications, recurring to intuitive commands and dynamic content that can proportionate more interesting and satisfying experiences. In parallel, polymer-based sensors and actuators, and their integration in different substrates or devices is an area of increasing scientific and technological interest, which current state of the art starts to permit the use of smart sensors and actuators embodied within the objects seamlessly. Electronics is no longer a rigid board with plenty of chips. New technological advances and perspectives now turned into printed electronics in polymers, textiles or paper. We are assisting to the actual scaling down of computational power into everyday use objects, a fusion of the computer with the material. Interactivity is being transposed to objects erstwhile inanimate. In this work, strain and deformation sensors and actuators were developed recurring to functional polymer composites with metallic and carbonaceous nanoparticles (NPs) inks, leading to capacitive, piezoresistive and piezoelectric effects, envisioning the creation of tangible user interfaces (TUIs). Based on smart polymer substrates such as polyvinylidene fluoride (PVDF) or polyethylene terephthalate (PET), among others, prototypes were prepared using piezoelectric and dielectric technologies. Piezoresistive prototypes were prepared with resistive inks and restive functional polymers. Materials were printed by screen printing, inkjet printing and doctor blade coating. Finally, a case study of the integration of the different materials and technologies developed is presented in a book-form factor.A última década foi marcada por uma alteração do paradigma de computador pelo súbito aparecimento dos tablets e smartphones para o público geral. A alteração de perspetiva do computador para os materiais como parte central de interação digital levou a uma diversificação dos contextos de interação, objetos e aplicações, recorrendo a comandos intuitivos e conteúdos dinâmicos capazes de tornarem a experiência mais interessante e satisfatória. Em simultâneo, sensores e atuadores de base polimérica, e a sua integração em diferentes substratos ou dispositivos é uma área de crescente interesse científico e tecnológico, e o atual estado da arte começa a permitir o uso de sensores e atuadores inteligentes perfeitamente integrados nos objetos. Eletrónica já não é sinónimo de placas rígidas cheias de componentes. Novas perspetivas e avanços tecnológicos transformaram-se em eletrónica impressa em polímeros, têxteis ou papel. Neste momento estamos a assistir à redução da computação a objetos do dia a dia, uma fusão do computador com a matéria. A interatividade está a ser transposta para objetos outrora inanimados. Neste trabalho foram desenvolvidos atuadores e sensores e de pressão e de deformação com recurso a compostos poliméricos funcionais com tintas com nanopartículas (NPs) metálicas ou de base carbónica, recorrendo aos efeitos capacitivo, piezoresistivo e piezoelétrico, com vista à criação de interfaces de usuário tangíveis (TUIs). Usando substratos poliméricos inteligentes tais como fluoreto de polivinilideno (PVDF) ou politereftalato de etileno (PET), entre outos, foi possível a preparação de protótipos de tecnologia piezoelétrica ou dielétrica. Os protótipos de tecnologia piezoresistiva foram feitos com tintas resistivas e polímeros funcionais resistivos. Os materiais foram impressos por serigrafia, jato de tinta, impressão por aerossol e revestimento de lâmina doctor blade. Para terminar, é apresentado um caso de estudo da integração dos diferentes materiais e tecnologias desenvolvidos sob o formato de um livro.This project was supported by FCT – Fundação para a Ciência e a Tecnologia, within the doctorate grant with reference SFRH/BD/110622/2015, by POCH – Programa Operacional Capital Humano, and by EU – European Union

Smart Platform for Low-Cost MEMS Sensors – Pressure, Flow and Thermal Conductivity

In a technological world that is trending towards smart and autonomous engineering, the collection of quality data is of unrivalled importance. This has led to a huge market demand for the development of low-cost, small and accurate sensors and thus has resulted in significant research into sensors, with the aim of advancing the price/performance ratio in commercial solutions. Micro Electro Mechanical Systems (MEMS) have recently offered an attractive solution to miniaturise and drastically improve the performance of sensors. In this thesis, MEMS technology is exploited to create a multi-sensor technology platform that is used to fabricate several sensing technologies. Piezo-resistive and piezo-electronic pressure sensors are designed, fabricated and tested. Different doping profiles, stress-engineered structures and electronic devices for pressure transduction are investigated, with focus on their sensitivity and non-linearity. A ring is fabricated in the metal layer around the circumference of the membrane that alleviates the effects of over/under etching. This is achieved by creating a new rigid edge of the membrane in the metal layer, which has tighter fabrication tolerances. A piezo-MOSFET is developed and shown to have greater sensitivity than similar state-of-the-art devices. Flow sensors based on a heated tungsten wire are designed, fabricated, tested and substantiated with numerical modelling. Calorimetric and anemometric driving modes are optimised with regards to device structure. Thermodiodes are also used as the temperature transduction devices and are compared to the traditional resistor method and showed to be preferable when further miniaturising the sensor. Thermal conductivity gas sensors based on a heated tungsten resistor are designed, tested and substantiated with numerical modelling. Holes through the membrane are used to improve the sensitivity to measuring carbon dioxide by 270%. Asymmetric holes are utilised to prove a novel method of measuring thermal conductivity in a calorimetric method. Designs improving this new concept are outlined and substantiated with analytical and numerical models. Linear statistical methods and artificial neural networks are used to differentiate flow rate and gas concentration using three on-membrane resistors. With membrane holes, the discrimination between gases in the presence of flow is improved. Neural networks provide a viable solution and show an increase in the accuracy of both flow rate and gas concentration. The main objective of the work in this thesis was to develop low-cost, low-power, small devices capable of high-volume production and monolithic integration using a single smart technology platform for fabrication. The smart technology platform was used to create pressure sensors, flow sensors and thermal conductivity gas sensors. Within each sensing technology, proof-of-concepts and optimisations have been carried out in order to maximise performance whilst using the low-cost, high-volume fabrication process, ultimately helping towards smart and autonomous engineering solutions driven by data

Моделювання структур чутливих елементів наноелектронних сенсорів

Використaння тонких плiвок у технiцi стaло можливим пiсля освоєння методiв їх одержaння з попередньо зaдaними фiзичними влaстивостями. Це вiдкрило можливiсть їх широкого зaстосувaння в сенсориці, як елементiв мiкроелектронних схем, тензодaтчикiв, датчиків магнітного поля тощо. Ці фактори і визначають актуальність даної роботи, а самі дослідження фізичних властивостей тонкоплівкових структур як чутливих елементів датчиків та сенсорів є важливими та своєчасними. Метою даної роботи є вивчення та аналіз функціональних та конструктивних особливостей тонкоплівкових сенсорів, а також елементів гнучкої електроніки спін-клапанного типу; розрахунок основних параметрів таких пристроїв. У результаті виконання кваліфікаційної роботи проведено аналітичний огляд стосовно конструкційних особливостей та фізичних принципів функціонування тонкоплівкових сенсорів, розглянуті типи матеріалів для їх створення

Structural Health Monitoring in Composite Structures: A Comprehensive Review.

This study presents a comprehensive review of the history of research and development of different damage-detection methods in the realm of composite structures. Different fields of engineering, such as mechanical, architectural, civil, and aerospace engineering, benefit excellent mechanical properties of composite materials. Due to their heterogeneous nature, composite materials can suffer from several complex nonlinear damage modes, including impact damage, delamination, matrix crack, fiber breakage, and voids. Therefore, early damage detection of composite structures can help avoid catastrophic events and tragic consequences, such as airplane crashes, further demanding the development of robust structural health monitoring (SHM) algorithms. This study first reviews different non-destructive damage testing techniques, then investigates vibration-based damage-detection methods along with their respective pros and cons, and concludes with a thorough discussion of a nonlinear hybrid method termed the Vibro-Acoustic Modulation technique. Advanced signal processing, machine learning, and deep learning have been widely employed for solving damage-detection problems of composite structures. Therefore, all of these methods have been fully studied. Considering the wide use of a new generation of smart composites in different applications, a section is dedicated to these materials. At the end of this paper, some final remarks and suggestions for future work are presented