Academic literature on the topic '3D printed sensors'

Three-dimensional (3D) printing has recently emerged as a novel approach in the development of electrochemical sensors. This approach to fabrication has provided a tremendous opportunity to make complex geometries of electrodes at high precision. The most widely used approach for fabrication is fused deposition modeling; however, other approaches facilitate making smaller geometries or expanding the range of materials that can be printed. The generation of complete analytical devices, such as electrochemical flow cells, provides an example of the array of analytical tools that can be developed. This review highlights the fabrication, design, preparation, and applications of 3D printed electrochemical sensors. Such developments have begun to highlight the vast potential that 3D printed electrochemical sensors can have compared to other strategies in sensor development.

Purpose The purpose of this paper is to investigate the process of rapid prototyping eddy current sensors using 3D printing technology. Making full use of the advantages of 3D printing, the authors study on a new method for fabrication of an eddy current sensor. Design/methodology/approach In this paper, the authors establish a 3D model using SolidWorks. And the eddy current sensor is printed by the fused deposition modeling method. Findings Measurement results show that the 3D printing eddy current sensor has a wider linear measurement range and better linearity than the traditional manufacturing sensor. Compared to traditional eddy current sensor fabrication method, this 3D printed sensor can be fabricated at a lower cost, and the fabrication process is more convenient and faster. Practical implications This demonstrated 3D printing process can be applied to the 3D printing of sensors of more sophisticated structures that are difficult to fabricate using conventional techniques. Originality/value In this work, the process of rapid prototyping eddy current sensors using 3D printing is presented. Sensors fabricated with the 3D printing possess lots of merits than traditional manufactures. 3D printed sensors can be customized according to the configuration of the overall system, thus reducing the demand of sensor's rigid mounting interfaces. The 3D printing also reduce design costs as well as shortens the development cycle. This allows for quick translation of a design from concept to a useful device.

The ability to directly print compliant biomedical devices on live human organs could benefit patient monitoring and wound treatment, which requires the 3D printer to adapt to the various deformations of the biological surface. We developed an in situ 3D printing system that estimates the motion and deformation of the target surface to adapt the toolpath in real time. With this printing system, a hydrogel-based sensor was printed on a porcine lung under respiration-induced deformation. The sensor was compliant to the tissue surface and provided continuous spatial mapping of deformation via electrical impedance tomography. This adaptive 3D printing approach may enhance robot-assisted medical treatments with additive manufacturing capabilities, enabling autonomous and direct printing of wearable electronics and biological materials on and inside the human body.

Eight chromophoric indicators are incorporated into Sylgard 184 to develop sensors that are fabricated either by traditional methods such as casting or by more advanced manufacturing techniques such as 3D printing. The sensors exhibit specific color changes when exposed to acidic species, basic species, or elevated temperatures. Additionally, material properties are investigated to assess the chemical structure, Shore A Hardness, and thermal stability. Comparisons between the casted and 3D printed sensors show that the sensing devices fabricated with the advanced manufacturing technique are more efficient because the color changes are more easily detected.

Three-dimensional printing by material extrusion enables the production of fully functional dynamic piezoelectric sensors in a single process. Because the complete product is finished without additional processes or assembly steps, single-process manufacturing opens up new possibilities in the field of smart dynamic structures. However, due to material limitations, the 3D-printed piezoelectric sensors contain electrodes with significantly higher electrical resistance than classical piezoelectric sensors. The continuous distribution of the capacitance of the piezoelectric layer and the resistance of the electrodes results in low-pass filtering of the collected charge. Consequently, the usable frequency range of 3D-printed piezoelectric sensors is limited not only by the structural properties but also by the electrical properties. This research introduces an analytical model for determining the usable frequency range of a 3D-printed piezoelectric sensor with resistive electrodes. The model was used to determine the low-pass cutoff frequency and thus the usable frequency range of the 3D-printed piezoelectric sensor. The low-pass electrical cutoff frequency of the 3D-printed piezoelectric sensor was also experimentally investigated and good agreement was found with the analytical model. Based on this research, it is possible to design the electrical and dynamic characteristics of 3D-printed piezoelectric sensors. This research opens new possibilities for the design of future intelligent dynamic systems 3D printed in a single process.

3D-printing technology is opening up new possibilities for the co-printing of sensory elements. While quasi-static research has shown promise, the dynamic performance has yet to be researched. This study researched smart 3D structures with embedded and printed sensory elements. The embedded strain sensor was based on the conductive PLA (Polylactic Acid) material. The research was focused on dynamic measurements of the strain and considered the theoretical background of the piezoresistivity of conductive PLA materials, the temperature effects, the nonlinearities, the dynamic range, the electromagnetic sensitivity and the frequency range. A quasi-static calibration used in the dynamic measurements was proposed. It was shown that the temperature effects were negligible, the sensory element was linear as long as the structure had a linear response, the dynamic range started at ∼ 30 μ ϵ and broadband performance was in the range of few kHz (depending on the size of the printed sensor). The promising results support future applications of smart 3D-printed systems with embedded sensory elements being used for dynamic measurements in areas where currently piezo-crystal-based sensors are used.

Presently, Electrical Capacitance Tomography (ECT) is positioned as a relatively mature and inexpensive tool for the diagnosis of non-conductive industrial processes. For most industrial applications, a hand-made approach for an ECT sensor and its 3D extended structure fabrication is used. Moreover, a hand-made procedure is often inaccurate, complicated, and time-consuming. Another drawback is that a hand-made ECT sensor’s geometrical parameters, mounting base profile thickness, and electrode array shape usually depends on the structure of industrial test objects, tanks, and containers available on the market. Most of the traditionally fabricated capacitance tomography sensors offer external measurements only with electrodes localized outside of the test object. Although internal measurement is possible, it is often difficult to implement. This leads to limited in-depth scanning abilities and poor sensitivity distribution of traditionally fabricated ECT sensors. In this work we propose, demonstrate, and validate experimentally a new 3D ECT sensor fabrication process. The proposed solution uses a computational workflow that incorporates both 3D computer modeling and 3D-printing techniques. Such a 3D-printed structure can be of any shape, and the electrode layout can be easily fitted to a broad range of industrial applications. A developed solution offers an internal measurement due to negligible thickness of sensor mount base profile. This paper analyses and compares measurement capabilities of a traditionally fabricated 3D ECT sensor with novel 3D-printed design. The authors compared two types of the 3D ECT sensors using experimental capacitance measurements for a set of low-contrast and high-contrast permittivity distribution phantoms. The comparison demonstrates advantages and benefits of using the new 3D-printed spatial capacitance sensor regarding the significant fabrication time reduction as well as the improvement of overall measurement accuracy and stability.

In this research, we present the development of 3D printed, highly stretchable and sensitive strain sensors using Graphene based composites. Graphene, a 2D material with unique electrical and piezoresistive properties, has already been used to create highly sensitive strain sensors. In this new study, by co-printing Graphene based Polylactic acid (PLA) with thermoplastic polyurethane (TPU), a highly stretchable and sensitive strain sensor based on Graphene composites can be 3D printed for the first time in strain sensors. The fabrication process of all materials is fully compatible with fused deposition modeling (FDM) based 3D printing method, which makes it possible to rapidly prototype and manufacture highly stretchable and sensitive strain sensors. The mechanical properties, electrical properties, sensitivity of the 3D printed sensors will be presented.

Fiber Bragg Gratings is a type of optical sensor used to measure temperature in many different fields. They have many advantages in relation to standard electric thermometers. The optical fiber and grating is cheap, these optical fiber sensor systems are expensive mainly due to the spectrum analyzer, so it is preferable to minimize the cost while keeping the accuracy as high as possible. By increasing the thermal response of the fiber it is possible to reduce the overall cost of the sensor system. The thermal response can be increased if a material with greater thermal expansion than the fiber is used as coating. Plastic is a coating material with potential due to its availability, low cost and high coefficient of thermal expansion. With 3Dprinting it is possible to choose from a large range of materials available and customize the functionality of the sensor. In this degree project we examined the functionality of a PLA coated Fiber Bragg Grating sensor where the coating was applied using a 3D-printer. Our findings shows that these type of sensors could meet the requirements if used within a specific temperature range.

Nowadays, we observe the transition for creation of the domestic and industry objects from the traditional methods involving the assembling of the different parts obtained by cutting, molding or otherwise to the additive manufacturing which refers to the object formation by using a layer-by-layer deposition of the versatile materials (metals, plastics, glasses, and so on) in the one 3D printing technological process. In the electronics, the attention should be given to the especially perspective technology, that is 3D ink printing of inks based on the metal nanoparticles (Ag, Cu, Sn) to obtain the printed circuit boards, charge-collecting contacts of thin-film solar cells and its connections with the external loads. Moreover, the inks based on the semiconductor materials (Cu2ZnSn(S,Se)4, ZnO) are the promising for the use in the sensitive elements of photoconverters, thermoelectric generators, transparent electronics, gas sensors, and touchpads.

Microfluidics is a continually growing field covering a wide range of applications, such as cellular analysis, biomarker quantification, and drug discovery; but in spite of this, the field of microfluidics remains predominately academic. New materials are pivotal in providing tailored properties to improve device integration and decrease prototype turnaround times. In biosensing, nonspecific adsorption in microfluidic systems can deplete target molecules in solution and prevent analytes, especially those at low concentrations, from reaching the detector. Polyethylene glycol diacrylate (PEGDA) mixed with photoinitiator forms, on exposure to ultraviolet (UV) radiation, a polymer with inherent resistance to nonspecific adsorption. Optimization of the polymerized PEGDA (poly-PEGDA) formula imbues this material with some of the same properties, including optical clarity, water stability, and low background fluorescence, that makes polydimethylsiloxane (PDMS) a widely used material for microfluidics. Poly-PEGDA demonstrates less nonspecific adsorption than PDMS over a range of concentrations of flowing fluorescently tagged bovine serum albumin solutions, and poly-PEGDA has greater resistance to permeation by small hydrophobic molecules than PDMS. Poly-PEGDA also exhibits long-term (hour scale) resistance to nonspecific adsorption compared to PDMS when exposed to a low (1 μg/mL) concentration of a model adsorptive protein. Electrophoretic separations of amino acids and proteins resulted in symmetrical peaks and theoretical plate counts as high as 4 × 105/m. Pneumatically actuated, non-elastomeric membrane valves fabricated from poly-PEGDA have been characterized for temporal response, valve closure, and long-term durability. A ∼100 ms valve opening time and a ∼20 ms closure time offer valve operation as fast as 8 Hz with potential for further improvement. Comparison of circular and rectangular valve geometries indicates that the surface area for membrane interaction in the valve region is important for valve performance. After initial fabrication, the fluid pressure required to open a closed circular valve is ∼50 kPa higher than the control pressure holding the valve closed. However, after ∼1000 actuations to reconfigure polymer chains and increase elasticity in the membrane, the fluid pressure required to open a valve becomes the same as the control pressure holding the valve closed. After these initial conditioning actuations, poly-PEGDA valves show considerable robustness with no change in effective operation after 115,000 actuations.Often, localized areas of surface functionalization are desired in biosensing, necessitating site-specific derivatization. Integration of poly-PEGDA with different substrates, such as glass, silicon, or electrode-patterned materials, allows for broad application in biosensing and microfluidic devices. Deposition of 3-(trimethoxysilyl) propyl methacrylate or (3-acryloxypropyl) dimethylmethoxysilane onto these substrates makes bonding to poly-PEGDA possible under UV exposure. Primary deposition of (3-acryloxypropyl) dimethylmethoxysilane, followed by photolithographic patterning, allows for silane removal through HF surface etching in the exposed areas and subsequent deposition of 3 aminopropyldiisopropylethoxysilane on the etched regions. Fluorescent probes are used to evaluate surface attachment methods. Primary attachment via reaction of Alexa Fluor 488 TFP ester to the patterned aminosilane demonstrates excellent fluorescent signal. Initial results with glutaraldehyde were demonstrated but require more optimization before this method for secondary attachment is viable. Fabrication of 3D printed microfluidic devices with integrated membrane-based valves is performed with a low-cost, commercially available stereolithographic 3D printer and a custom PEGDA resin formulation tailored for low non-specific protein adsorption. Horizontal microfluidic channels with designed rectangular cross sectional dimensions as small as 350 µm wide and 250 µm tall are printed with 100% yield, as are cylindrical vertical microfluidic channels with 350 µm designed (210 µm actual) diameters. Valves are fabricated with a membrane consisting of a single build layer. The fluid pressure required to open a closed valve is the same as the control pressure holding the valve closed. 3D printed valves are successfully demonstrated for up to 800 actuations. Poly-PEGDA is a versatile material for microfluidic applications ranging from electrophoretic separations, valve implementation, and heterogeneous material integration. Further improvements in PEGDA resin formulation, in combination with a UV source 3D printer, will provide poly-PEGDA devices that are not only rapidly fabricated (<40 min per device), but that also include pumps and valves and are usable with a variety of detection methods, such as laser-induced fluorescence and immunoassays, for broad application in biosensing.

Thesis is dealing with the creation of robotic worplace and its periphery. The paper is discrabing the robotic function and kinematics. The practical part of the paper shows several types of suggested robotic workplaces followed by solution processing of one selected type, where technical documentation and the calculation of production is made. The end of the paper shows economical and technological evaluation of the selected type of workplace including the price returns.

L’objectif de ce travail était de concevoir et réaliser par impression un capteur acoustique capacitif résonant bas coût. Il s’inscrit dans le cadre d’un projet collaboratif de recherche intitulé « Spinnaker », défini par la société Tagsys RFID qui souhaite intégrer ce capteur afin d’améliorer la géolocalisation des étiquettes RFID. Ce travail a débuté par la conception et l’optimisation du design en utilisant la simulation par éléments finis (COMSOL) ainsi que des plans d’expériences (DOE : Design of Experiment). Cette première étape a permis de déterminer les paramètres optimaux et démontrer que les performances obtenues étaient conformes aux spécifications. Nous avons ensuite développé les différentes briques technologiques nécessaires à la réalisation des prototypes en utilisant conjointement l’impression 2D par inkjet et l’impression 3D. Nous avons vérifié la fonctionnalité de ces capteurs à l’aide de mesures électriques capacitives et acoustiques par vibrométrie laser. Nous avons démontré la sélectivité en fréquence des capteurs réalisés et comparé les résultats expérimentaux à ceux obtenus par simulation. Enfin, nous avons enfin exploré la « voie piezoélectrique » qui nous semble être une alternative intéressante au principe capacitif. En l’absence d’encre piézoélectrique commerciale imprimable par jet de matière, nous avons formulé une encre imprimable à base du co-polymère PVDF-TrFE et démontré le caractère piézoélectrique des couches imprimées. Les résultats sont prometteurs mais des améliorations doivent encore être apportées à cette encre et au procédé d’impression avant de pouvoir fabriquer des premiers prototypes
The objective of this work was to design and fabricate a low cost resonant capacitive acoustic sensor using printing techniques. It falls within the frame of a collaborative research project named “Spinnaker”, set up by TAGSYS RFID, a French company, which has planned to integrate this sensor to improve the geolocalization of their RFID tags. This work started with the design and optimization of the sensor using finite element modeling (COMSOL) and design of experiments (DOE). This first step has enabled the identification of the optimum set of parameters and demonstrated that the output responses were in accordance with the specifications. Then, we have developed the different technological building blocks required for the fabrication of the prototypes using jointly the 2D inkjet printing technique and 3D printing method. The functionality of the sensors has been characterized using both capacitive and acoustic measurements using laser Doppler vibrometer. Experimental results showed that sensitivity and selectivity were within the specifications and in good agreement with the modeling results. Finally, we investigated the piezoelectric approach which could be an interesting option to the capacitive one. Since no inkjet printable piezoelectric ink is commercially available, stable inkjet printable polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) ink has been developed. PVDF-TrFE layers were then successfully printed and characterized. The results were quite promising, however further improvements of the ink and printing process are required before stepping towards piezoelectric based device fabrication

Tese de mestrado integrado em Engenharia Biomédica e Biofísica (Engenharia Clínica e Instrumentação Médica), Universidade de Lisboa, Faculdade de Ciências, 2020
Nos últimos anos tem-se vindo a registar um aumento do interesse, por parte da comunidade científica, pela área dos exosqueletos, onde novos modelos e conceitos são constantemente apresentados, com o objetivo de desenvolver a próxima geração de dispositivos. Uma das razões que pode vir a justificar este aumento de interesse, por parte da comunidade científica, é o aumento da esperança média de vida. De acordo com a organização mundial de saúde, a percentagem de população mundial com mais de 60 anos aumentará de 11% para 22%, entre 2000 e 2050. Com o aumento da esperança média de vida, espera-se também um aumento da incidência de doenças associadas ao envelhecimento que, em muitos dos casos, podem levar a incapacidades motoras. Como tal, é necessário desenvolver dispositivos capazes de assistir indivíduos que se encontrem nestas situações. Uma possível medida a implementar, seria o desenvolvimento de exosqueletos dedicados à reabilitação, assim como dispositivos capazes de assistir indivíduos com deficiências locomotoras, no seu dia-a-dia. Com a perspetiva do aumento da esperança média de vida, é também importante adotar medidas de prevenção, de modo a evitar complicações no futuro, ao nível do sistema locomotor, especialmente para pessoas com trabalhos mais físicos. Estas complicações poderiam ser potencialmente reduzidas com a aplicação de exosqueletos nos variados locais de trabalho, com vista a melhorar a postura e desempenho dos trabalhadores, auxiliando-os nas suas tarefas diárias. Independentemente do objetivo para qual o exosqueleto está a ser desenvolvido, é essencial que o mesmo tenha uma boa estratégia de controlo. Existem várias estratégias de controlo, sendo uma delas o controlo baseado na força/torque aplicado pelo utilizador. Neste tipo de controlo, como o nome indica, a força/torque aplicado pelo exosqueleto é proporcional à leitura de sensores que se encontram entre o utilizador e o exosqueleto, que indiretamente interpretam a intenção do utilizador. Estes sensores são normalmente sensores de eletromiografia (EMG) e/ou sensores de força. Para além de uma boa estratégia de controlo é também importante monitorizar as forças de interação entre o exosqueleto e o utilizador. A incorreta aplicação de forças, por parte do exosqueleto, pode levar à alteração do padrão natural de ativação dos músculos, sendo por sua vez contraprodutivo no caso da fisioterapia, por exemplo. Por outro lado, forças que são incorretamente aplicadas podem também desencadear fadiga, desconforto e, em último caso, colocar em risco a segurança do utilizador. Como tal, a monitorização das forças aplicadas pelo exosqueleto é algo verdadeiramente importante, que pode ser executado através da implementação de sensores de força. A partir da informação apresentada, é possível concluir que a integração de sensores de EMG e força nas interfaces dos exosqueletos é uma possível estratégia a adaptar, quando o objetivo é otimizar o desempenho dos mesmos. No entanto, não existem muitos casos de exosqueletos com este tipo de sensores incorporados. Uma das razões que pode vir a justificar este fenómeno é a geometria deste tipo de sensores, que se encontram atualmente no mercado, ser fixa e de difícil customização, o que influencia diretamente o design do exosqueleto. Para além da geometria dos sensores, na maioria dos casos, quando o objetivo é fabricar sensores de alta resolução, o processo de fabrico é constituído por múltiplas etapas, o que pode dificultar a escalabilidade de manufatura, aumentando o custo de fabrico, o que em última instância comprometerá o design e o processo de fabricação dos exosqueletos. Com o objetivo de encontrar alternativas aos sensores convencionais, alguns desenvolvimentos têm sido feitos numa tentativa de incorporar a tecnologia de impressão 3D ao mundo dos sensores. Uma das grandes vantagens desta simbiose é a possibilidade de poder, numa só etapa, produzir e integrar o sensor, sem limitações de design, no local desejado, neste caso na interface do exosqueleto. Como tal, o objetivo deste trabalho seria o desenvolvimento de uma interface de um exosqueleto, impressa em 3D, com sensores de EMG e de força incorporados, também impressos em 3D. O exosqueleto que será utilizado provirá de um projeto em desenvolvimento pelo grupo Brussels Human Robotics Research Center, BruBotics, mais especificamente pelo projeto BioMot. Neste projeto em específico, devido à complexidade do objetivo estipulado, apenas os sensores de EMG e de força, impressos em 3D, foram desenvolvidos e testados. Para além dos sensores, um estudo sobre a deformação dos músculos da parte inferior da perna, durante ciclo de marcha, foi também realizado, de modo a facilitar o futuro design da interface do exosqueleto. Um sensor de EMG é constituído por dois elétrodos condutores, isolados por um material não condutor, de modo a possibilitar a captação dos sinais elétricos provenientes dos músculos, que, por sua vez, refletem a intenção do utilizador. Como tal, para produzir este tipo de sensores, utilizando técnicas de impressão 3D, mais especificamente, técnicas de impressão FDM (modelagem por deposição fundida), é preciso: um material condutor (neste caso semicondutores, devido à inexistência de filamentos condutores, para este tipo de impressão 3D) e um material não condutor. Para este projeto foram utilizados: o filamento semicondutor Proto-pasta conductive PLA (Protoplant, Inc., USA) e o filamento não condutor Ultimaker TPU 95A (Ultimaker B.V., The Netherlands). Com estes dois materiais foi possível, com algumas limitações, produzir um sensor EMG funcional, que poderá, possivelmente, vir a ser integrado num exosqueleto, em trabalho futuro. É necessário, no entanto realizar primeiro um estudo intensivo, de modo a compreender as restrições de funcionamento deste mesmo sensor. Relativamente aos sensores de força, o seu design/modo de funcionamento, foi baseado num condensador de elétrodos paralelos. De forma a produzir este tipo de sensor, é necessário um material semicondutor (dado, mais uma vez, a inexistência de materiais condutores para o tipo de técnica de impressão 3D que será utilizado) e um material não condutor. A ideia seria imprimir um sensor com duas finas placas semicondutoras, separadas por outra fina placa não condutora, denominado de dielétrico. Neste tipo de sensores, quando uma força é aplicada, a distância entre as placas semicondutoras diminui, induzindo um aumento da capacidade do condensador, sendo que este aumento será proporcional à força aplicada ao sensor, permitindo assim o seu registo. Com o objetivo de desenvolver este tipo de sensor, foi necessário primeiro desenvolver um sistema capaz de captar, e posteriormente transferir para um computador, as variações da capacidade do sensor de forma a possibilitar a sua posterior análise. Para além do sistema de registo, foi também necessário testar vários tipos de materiais e as várias definições de impressão, de modo a selecionar quais os mais adequados para a impressão deste sensor, dado que. Neste caso, os materiais e as definições de impressão mais adequadas, seriam as que conferissem ao dielétrico a maior flexibilidade possível dado que, quanto maior a flexibilidade do dielétrico, maior a variação da capacidade, e, como tal, maior resolução dos sinais captados. Após o desenvolvimento de um sistema de registo, e da escolha dos materiais mais adequados ao objetivo deste projeto, um sensor capacitivo foi produzido. As placas condutoras foram impressas com o filamento PI-ETPU 95-250 Carbon Black (Palmiga Innovation, Sweden) e o dielétrico com o filamento não condutor NinjaFlex 85A (Fenner Inc., USA). Ao contrário das placas condutoras, o dielétrico foi impresso com um preenchimento concêntrico ocupando apenas 50% do espaço, conferindo deste modo uma maior flexibilidade ao sensor. Com a produção do sensor completa, o mesmo foi testado. A partir dos resultados dos testes realizados, foi possível verificar um aumento da capacidade do sensor quando sujeito à aplicação de uma força, sendo que este aumento foi proporcional à magnitude da força aplicada. Apesar dos resultados terem sido bastante positivos, o sensor demonstrou ter uma elevada histerese, como tal, antes da implementação destes sensores em exosqueletos, os mesmos terão de ser rigorosamente testados, com vista a melhor compreender as suas limitações e modular, se possível, a resposta dos sensores tendo em conta a sua histerese, dependência do tempo de aplicação das forças, entre outros fatores. Após o desenvolvimento dos dois tipos de sensores, foi crucial compreender qual o melhor local para os aplicar, de modo a otimizar a informação proveniente dos sinais, por eles captados. Seguindo esta ordem de pensamentos, um algoritmo foi desenvolvido de modo a melhor compreender a deformação da superfície da parte inferior da perna, e como tal dos músculos que a constituem, durante o ciclo de marcha. Esta informação é especialmente relevante aquando da implementação dos sensores de EMG, dado que os locais onde os mesmos devem ser colocados, correspondem à zona mais proeminente dos músculos que estão a ser avaliados, que naturalmente estão sujeitos a maiores níveis de deformação. Para compreender quais os vários locais de deformação da parte inferior da perna, vários varrimentos de imagem (scans) de vários indivíduos, em várias fases do ciclo de marcha, foram obtidos, e comparados entre si, através do algoritmo desenvolvido, nestes scans as parte mais proeminentes dos músculos em estudo foram assinaladas com marcadores. O algoritmo desenvolvido tem a capacidade de identificar, com algum erro associado, os marcadores, alinhar os diversos scans das várias fases do ciclo de marcha, com base na localização espacial desses mesmos marcadores e segmentar transversalmente os scans, nas zonas mais proeminentes dos músculos. A análise da deformação é feita a partir do raio de curvatura deste segmento em zonas especificas previamente estipuladas. Apesar do algoritmo precisar de alguns melhoramentos, de forma a possibilitar uma avaliação pormenorizada e exata da deformação da superfície da parte inferior da perna, foi possível concluir, a partir dos resultados de saída do algoritmo, que as maiores deformações ocorrem nos limites dos músculos e não nas zonas mais proeminentes dos músculos (apesar de existir um deslocamento espacial das mesmas zonas). Esta informação será bastante relevante para a construção da interface do exosqueleto, mais especificamente para a escolha dos materiais, mais rígidos ou mais flexíveis por exemplo, e onde os corretamente colocar, de modo a assegurar o constante contacto entre o utilizador e os sensores, enquanto a eficiência do exosqueleto é assegurada.
There has been an increasing interest on the research of exoskeletons in the last years, with novel designs and concepts emerging to develop the next generation of devices. One of many research areas, involved in the optimization of the exoskeletons’ performance, is the integration of sensors, more specifically Electromyography (EMG) sensors and force sensors, into the exoskeleton’s interfaces, being the interfaces, the exoskeleton’s component responsible for the power transmission from the exoskeleton to the user’s biological structures. The integration of sensors into the exoskeletons’ interfaces can potentially improve the exoskeleton’s control, comfort, safety, and ergonomics. However, the integration of the sensors that are currently on the market into the exoskeletons’ interfaces has complications such as the sensors’ fixed geometry, lack of customisation and fabrication costs. One alternative to these conventional sensors is combining the 3D printing technology to the sensor’s world and produce 3D printed orthosis embedded with 3D printed sensors, where an integrated manufacturing strategy can be adopted, allowing the production of customized interfaces. Therefore, the goal of this project was to develop and test 3D printed EMG and force sensors to be integrated, in future work, into the cuffs of 3D printed orthotic devices. To help the design of these orthotic devices, an analysis of the deformation of the lower limb muscles, during the gait cycle will was also performed. In this project a working 3D printed EMG sensor, along with a 3D printed capacitance-based force sensor were successfully produced, also an efficient reading system for the force sensor was developed. Besides the 3D printed sensors, an algorithm, able to detect possible deformations, and measure those same deformations, was developed. From the algorithm’s results, it was possible to conclude the existence of variations in the muscle’s limits due to changes in the gait cycle positions.

The Additive Manufacturing has been developing more and more, providing numerous advantages to the industry. Among such advantages is the use of materials with conductive properties combined with 3D printing techniques, which enables development of new devices embedded in plastic elements. One of the industries where Additive Manufacturing methods can be applied most successfully is the automotive industry. The electrification of cars, connected cars, autonomous driving, equipment enriched with sensors for better comfort are some of the challenges that this industry faces. Thus, innovation is made in the sense of developing new products to meet the presented challenges, always focusing on the user. Thus, this Master Thesis aims to study, explore and expand these concepts and apply them to the development of a touch sensor, as well as to understand what are the problems of compatibility and electromagnetic interference that can be encountered in automotive environment, specifically, in a smart door for a car. This work begins with the study of Additive Manufacturing methods, the types of measurements for a touch sensor, the sensor designs, and the electromagnetic compatibility and interference issues relevant for such sensors. Useful tools are developed to calculate the sensor capacitance, inductance and resonant frequency. Also, a script is developed to obtain the structural parameters for the resonant frequencies in desired ranges. These tools made it possible to develop a macro to automate creation of 3D structures in CST Studio Suite and thus to be able to simulate such structures for a large set of obtained parameters. Based on the simulations, we designed two sensor structures operating at the desired frequencies and, with the 3D structures ready, moved on to the experimental measurements, producing a PCB prototype for each structure. Thus, by completing these procedures it was concluded that the experimental measurements allowed us to test the developed tools and models and to validate the entire study.
A Manufatura Aditiva tem vindo a desenvolver-se cada vez mais, proporcionando inúmeras vantagens à indústria. Dentro delas a utilização de um material com propriedades condutoras e aliado a técnicas de impressão 3D, permite desenvolver novos dispositivos embutidos/incorporados numa peça de plástico. Uma das indústrias que mais se pode aplicar métodos de Manufatura Aditiva é a indústria automóvel. A eletrificação dos automóveis, os carros conetados, condução autónoma, a sonorização dos equipamentos e o conforto são alguns dos desafios que esta indústria enfrenta. Assim, a inovação faz-se no sentido de desenvolvimento de produtos para responder aos desafios apresentados, sempre com o foco no utilizador. Assim, esta Dissertação de Mestrado tem como objetivo estudar, explorar e expandir estes conceitos e aplicá-los ao desenvolvimento de um sensor de toque, além de perceber quais os problemas de compatibilidade e interferências eletromagnéticas num ambiente automóvel, mais concretamente numa porta inteligente para um carro. O trabalho iniciou-se com o estudo dos métodos de Manufatura Aditiva, tipos de medidas para um sensor de toque, design, compatibilidade e interferência eletromagnética destes sensores. Desenvolveram-se ferramentas para auxílio dos cálculos de capacitância, indutância e frequência de ressonância. Também se elaborou um script para obtenção dos parâmetros das frequências de ressonância nas gamas desejadas. Estas ferramentas possibilitaram o desenvolvimento de uma macro para criar as estruturas 3D num simulador e, assim, poder simular os parâmetros obtidos. Com as simulações alcançaram-se duas estruturas nas frequências desejadas e com as estruturas 3D criadas passámos à medição experimental, produzindo uma Printed Circuit Board (PCB) para cada estrutura. Assim, com estes processos, concluiu-se que as nossas medições experimentais permitem validar as ferramentas desenvolvidas, assim como todo o estudo e teoria desenvolvida.
Mestrado em Engenharia Eletrónica e Telecomunicações

A technical project alongside the University courses can deepen the understanding and increase the motivation for the subject of choice. As a student, there is often a hurdle to start such a project because of a lack of inspiration. And even after overcoming this, the costs associated with such a project may put students off. With my project I show how a 3rd semester Mechanical Engineering student can design and manufacture a rocket engine with all testing components on a student budget. Cost structure and resource planning are explained in detail. I launched the project in December 2020 and in September 2021 it was presented at the StuFoExpo21. A general curiosity for the topic and a basic understanding of mechanical engineering was sufficient for starting the project. Importantly, I gained the most valuable knowledge during the implementation of the project, through active failure-iteration and reading specialised literature. The project is focussed on the design and manufacturing of a rocket engine and its testing components. A special feature is the cooling jacket of the combustion chamber. It has been 3D printed in the SLUB Makerspace, a facility at TU Dresden. Further work packages of the project were the programming of sensors and control systems, first open-air combustion tests of the injector head, safety checks and a Risk & Safety analysis. The first testing and other preliminary work were performed in collaboration with fellow students. During the entire design and manufacturing process I was in continuous exchange with the research group “Space Transportation” of the Institute of Aerospace Engineering at TU Dresden. Special thanks go to Dipl.-Ing. Jan Sieder-Katzmann and Dipl.-Ing. Maximilian Buchholz for their help during this process. For 2022 I plan a test campaign of the rocket engine to collect sensor data and to perform engine thrust measurements.

AbstractThe article discusses the design of an acquisition system for the 3D surface of human arms. The system is composed by a 3D optical scanner implementing stereoscopic depth sensors and by an acquisition software responsible for the processing of the raw data. The 3D data acquired by the scanner is used as starting point for the manufacturing of custom-made 3D printed casts. Specifically, the article discusses the choices made in the development of an improved version of an existing system presented in [1] and presents the results achieved by the devised system.

Abstract Mechanical vibration isolation is an important element for many traditional MEMS devices, (e.g., MEMS inertial sensors and micro-optics) that are deployed in harsh environments (e.g., aerospace applications or automotive applications). Without suitable vibration isolation, environmental vibrations can potentially damage these devices. Micro-scale mechanical vibration isolators usually consist of a center proof mass pad, a suspension system, and a surrounding frame. The isolator functions as a mechanical low-pass filter that provides useful attenuation of high frequency environmental vibrations between the frame and the proof mass pad, to which the vibration sensitive device is attached. These vibration isolators are usually fabricated with either laser processing or silicon micromachining techniques. Although these traditional techniques produce high quality vibration isolators, these methods take time to develop for specific sensor applications, and the batch size is typically large. This paper has two key highlights. First, the efficacy of 3D printing as a prototyping tool for small batch MEMS sensor vibration isolation applications is considered. Twenty-five mechanical vibration isolators were tested for this investigation, using both SLA and FDM printers. The resulting test data demonstrated that the MEMS-scale 3D printed mechanical vibration isolators can be a valid option for real-world vibration isolation applications. Second, it is unclear whether the bulk material properties are valid for MEMS-scale 3D printed structures, since these bulk material properties are typically calculated using tensile tests on macro-scale dog-bone specimens. Considerable variation in vibratory system parameters was found, even when the same printer, print orientation, material, and post-processing were used.

Abstract 3D printing technologies have advanced significantly in recent years allowing for additive manufacturing of new structured materials, expanding the range, function, and capabilities of manufactured components. In this work, flexible capacitors were produced using additive manufacturing and compared to commercially available capacitance sensors in strain testing. The sensors utilize thermoplastic polyurethane (TPU) printed using fused filament fabrication methods as a dielectric substrate and a combination of flexible inks for production of the conductive surface. Flexible inks were printed using syringe based deposition methods on a custom designed printer using the TPU substrate. Results demonstrated successful capacitor production with capacitance values ranging from 2–70 pF depending on geometry, material, and printing conditions. The 3D printed flexible capacitors were characterized over a frequency range of 100 Hz to 10 kHz and compared to commercial roll-to-roll produced capacitors. Strain testing was conducted from 0–50% strain using a mechanical testing machine for the range of sensors and final capacitance post strain was measured to calculate deviation from original capacitance values. The sensors exhibited a relatively linear increase in capacitance when strained and returned to a resting position upon release of strain with minimal hysteresis effects, demonstrating their utility as 3D printed sensors.

Abstract Recent developments in materials and processes for additive manufacturing (AM) have moved 3D printing beyond just prototyping of manufactured parts and into exciting new applications. For example, various researchers and industries have successfully demonstrated the use of conductive filler modification in materials for use with fused deposition modeling (FDM)-based 3D printers. Due to the piezoresistive effect, these conductive filler-modified materials can be used to print highly customizable sensors on-demand. This is notable because combined with the versatility of FDM printing, it allows for a completely new interpretation of what a sensor is and what a sensor should look like. The accuracy and reliability of these sensors is still under investigation, and common AM materials such as polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) have been the subject of most investigations. Thermoplastic polyurethane (TPU), a commercially available flexible filament, has been less studied for conductive filler modification and printed sensors. This is an important gap in the state of the art because flexible sensors are becoming increasingly important in applications involving large deformations such as soft robotics. Therefore, this work presents the results of an initial study on the development of a carbon nanofiber (CNF)-modified TPU for the development of flexible piezoresistive-based printed sensors. Specifically, this work considers the effect of different manufacturing parameters on CNF/TPU conductivity and printability using a commercially available FDM printer. Ultimately, this project seeks to utilize the proposed functionalized TPU material for the production of embedded sensors in rigid or flexible 3D printed parts.

Abstract This paper reports on the design, fabrication, and evaluation of a novel 3D printed vacuum based soft sensor and its application as hand motion sensor. Soft sensors are an integral part of soft robotics as an emerging field of science that enables safe and easy human to machine interaction. The conventional sensors used to interface with humans in robotic systems are mechanically incompliant. Because of this mechanical compliance mismatch, these sensors cause unsafe interactions with humans. Recent advancements in 3D printing technology have allowed fabrication of complex geometries with soft polymers, perfect for more delicate and user-friendly sensors. While the existing soft pneumatic sensors work based on the positive pressure due to deformation, the proposed sensor in this work works based on vacuum due to deformation. In comparison with the similar positive pressure sensor, our vacuum-based sensor is much softer and has minimum interference with hand motion. Finite element analysis (FEA) is used to analyze the design. Also, a kinematic model of the hand is developed using Matlab to visualize the hand motion based on the sensor data. This could show the potential application of the soft hand motion sensor in virtual reality and telehealth.

Abstract Flexible sensors have demonstrated great potential for utilization in many industrial applications due to their ability to be produced in complex shapes. Sensors are employed to monitor and detect changes in the surrounding environment or the structure itself. A great majority of these flexible structures are produced by casting processes, since they are generally composed of silicone materials due to their high elasticity and flexibility. Unfortunately, the casting process is time consuming, and it limits the development of complex geometries reducing the advantages of silicone materials. 3D printed flexible sensors have demonstrated great potential for utilization in a variety of different applications including healthcare, environmental sensing, and industrial applications. In recent years, research on these topics has increased to meet low-cost sensing needs due to the development of innovative materials and printing techniques that reduce cost, production time, and enhance the electrical and mechanical properties of the sensors. This paper presents a 3D printed flexible dielectric electroactive polymer (DEAP) sensor capable of producing an output signal based on the deformation caused by external forces. Three different conductive flexible filaments were tested, using one commercial filament and two custom-made filaments, a comparison of its sensing behavior is also presented herein. Additionally, computational simulations were done to evaluate the performance of the produced sensors, evaluating the capacitance change of the entire structure. This work demonstrates the production of 3D printed flexible sensors and studies the behavior of new customizable conductive flexible filaments. Both manufactured sensors were produced using fused deposition modeling (FDM) techniques.

Abstract Flexible and sensitive strain sensors can be utilized as wearable sensors and electronic devices in a wide range of applications, such as personal health monitoring, sports performance, and electronic skin. This paper presents the fabrication of a highly flexible and sensitive strain sensor by 3D printing an electrically conductive polydimethylsiloxane (PDMS)/multi-wall carbon nanotube (MWNT) nanocomposite on a PDMS substrate. To maximize the sensor’s gauge factor, the effects of MWNT concentration on the strain sensing function in nanocomposites are evaluated. Critical 3D printing and curing parameters, such as 3D printing nozzle diameter and nanocomposites curing temperature, are explored to achieve the highest piezoresistive response, showing that utilizing a smaller deposition nozzle size and higher curing temperature can result in a higher gauge factor. The optimized 3D printed nanocomposite sensor’s sensitivity is characterized under cyclic tensile loads at different maximum strains and loading rates. A linear piezoresistive response is observed up to 70% strain with an average gauge factor of 12, pointing to the sensor’s potential as a flexible strain sensor. In addition, the sensing function is almost independent of the applied load rate. The fabricated sensors are attached to a glove and used as a wearable sensor by detecting human finger and wrist motion. The results indicate that this 3D printed functional nanocomposite shows promise in a broad range of applications, including wearable and skin mounted sensors.