12,701 research outputs found

    The application of impantable sensors in the musculoskeletal system: a review

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    As the population ages and the incidence of traumatic events rises, there is a growing trend toward the implantation of devices to replace damaged or degenerated tissues in the body. In orthopedic applications, some implants are equipped with sensors to measure internal data and monitor the status of the implant. In recent years, several multi-functional implants have been developed that the clinician can externally control using a smart device. Experts anticipate that these versatile implants could pave the way for the next-generation of technological advancements. This paper provides an introduction to implantable sensors and is structured into three parts. The first section categorizes existing implantable sensors based on their working principles and provides detailed illustrations with examples. The second section introduces the most common materials used in implantable sensors, divided into rigid and flexible materials according to their properties. The third section is the focal point of this article, with implantable orthopedic sensors being classified as joint, spine, or fracture, based on different practical scenarios. The aim of this review is to introduce various implantable orthopedic sensors, compare their different characteristics, and outline the future direction of their development and application

    Fabrication of low-cost and environmental-friendly EHD printable thin film nanocomposite triboelectric nanogenerator using household recyclable materials

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    Humans generate massive amounts of plastic and electronic waste, which pollute our environment, particularly our water supplies, and cause fatal difficulties. In addition, the increased use of fossil fuels is wreaking havoc on the ecosystem. In order to solve these issues, we describe a simple, low-cost, and environmentally-friendly triboelectric nanogenerator (TENG) made of electronic waste and recycled plastic, and we add nanomaterial to improve power generation using biomechanical energy. The present investigation involves synthesizing carbon dots (CDs) nano-material through a single-step hydrothermal technique and CDs nano-material characterized via UV.Vis Spectroscopy. The proposed carbon dot-graphite nano composite-based TENGs (CGC-TENGs) are created by reusing dry cells (electronic waste) to obtain graphite, plastic bottles to obtain plastic, and synthesized CDs. CGC-TENGs manufactures a simple, low-cost, and environmentally friendly In-house quick and bulk fabrication printed electro hydrodynamics (EHD) electrospray process that uses less solvent and does not require specialist equipment or knowledge. Comparing fabricate TENG device results, in which CDs used produced high voltage (127.31 V)/current (107.12 ÎŒA), while not using CDs produced low voltage (95.23 V)/current (104.12 ÎŒA) at similar fabrication parameters, the size of the devices are 4.5 cm × 7 cm, and 15 N force applied. The CGC-TENG (ÎŽ) has maximum output performance and is thoroughly investigated using an open-circuit voltage of 171.30 V, a short circuit current of 111.39 ÎŒA, and a maximum output power density of 53.08 ÎŒW/cm2. CGC-TENG (ÎŽ) was used to power an electronic glucose monitoring device, and twenty-three blue light-emitting diodes (LEDs) to demonstrate its practical applications. The approach we propose produces renewable energy sources by reutilizing plastic waste and technological waste, providing a practical and sustainable path toward our goal of creating a green planet

    Review of flexible energy harvesting for bioengineering in alignment with SDG

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    To cater to the extensive body movements and deformations necessitated by biomedical equipment flexible piezoelectrics emerge as a promising solution for energy harvesting. This review research delves into the potential of Flexible Piezoelectric Materials (FPM) as a sustainable solution for clean and affordable energy, aligning with the United Nations' Sustainable Development Goals (SDGs). By systematically examining the secondary functions of stretchability, hybrid energy harvesting, and self-healing, the study aims to comprehensively understand these materials' mechanisms, strategies, and relationships between structural characteristics and properties. The research highlights the significance of designing piezoelectric materials that can conform to the curvilinear shape of the human body, enabling sustainable and efficient mechanical energy capture for various applications, such as biosensors and actuators. The study identifies critical areas for future investigation, including the commercialization of stretchable piezoelectric systems, prevention of unintended interference in hybrid energy harvesters, development of consistent wearability metrics, and enhancement of the elastic piezoelectric material, electrode circuit, and substrate for improved stretchability and comfort. In conclusion, this review research offers valuable insights into developing and implementing FPM as a promising and innovative approach to harnessing clean, affordable energy in line with the SDGs.</p

    Model order reduction and stochastic averaging for the analysis and design of micro-electro-mechanical systems

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    Electro-mechanical systems are key elements in engineering. They are designed to convert electrical signals and power into mechanical motion and vice-versa. As the number of networked systems grows, the corresponding mathematical models become more and more complex, and novel sophisticated techniques for their analysis and design are required. We present a novel methodology for the analysis and design of electro-mechanical systems subject to random external inputs. The method is based on the joint application of a model order reduction technique, by which the original electro-mechanical variables are projected onto a lower dimensional space, and of a stochastic averaging technique, which allows the determination of the stationary probability distribution of the system mechanical energy. The probability distribution can be exploited to assess the system performance and for system optimization and design. As examples of application, we apply the method to power factor correction for the optimization of a vibration energy harvester, and to analyse a system composed by two coupled electro-mechanical resonators for sensing applications

    Review of flexible energy harvesting for bioengineering in alignment with SDG

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    To cater to the extensive body movements and deformations necessitated by biomedical equipment flexible piezoelectrics emerge as a promising solution for energy harvesting. This review research delves into the potential of Flexible Piezoelectric Materials (FPM) as a sustainable solution for clean and affordable energy, aligning with the United Nations' Sustainable Development Goals (SDGs). By systematically examining the secondary functions of stretchability, hybrid energy harvesting, and self-healing, the study aims to comprehensively understand these materials' mechanisms, strategies, and relationships between structural characteristics and properties. The research highlights the significance of designing piezoelectric materials that can conform to the curvilinear shape of the human body, enabling sustainable and efficient mechanical energy capture for various applications, such as biosensors and actuators. The study identifies critical areas for future investigation, including the commercialization of stretchable piezoelectric systems, prevention of unintended interference in hybrid energy harvesters, development of consistent wearability metrics, and enhancement of the elastic piezoelectric material, electrode circuit, and substrate for improved stretchability and comfort. In conclusion, this review research offers valuable insights into developing and implementing FPM as a promising and innovative approach to harnessing clean, affordable energy in line with the SDGs.</p

    Role of Ethanolamine on the Stability of a Sol-Gel ZnO ink

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    This work presents a detailed structural and chemical characterization of the system formed by zinc acetate dihydrate (ZAD) and ethanolamine (EA) with methoxyethanol (ME), in order to describe its stability. The origin of the mixture degradation during storage at room conditions is analyzed. Complementary computational (or theoretical) DFT calculations on the precursor formed in this reaction in ME and those of EA (free or in the same solvent) and in the presence or absence of CO2, light or both simultaneously are also reported in order to clarify the relative weight of these factors in the degradation process. In all cases, the models were tested as potential energy minimum and their photo-absorption spectra were simulated. The calculations show that the monomeric species formed in this process tend to assembly into dimers, which are more photosensitive and reactive than the monomer. Our results explain the experimental observations and provide a better understanding of the role played by EA, ME and CO2 in the formation of ZnO and, consequently, allow optimizing the technological processes to prepare these films

    Modellbasierte Simulation und Kalibrierung eines multimodalen Systems aus OCT und Optoakustik zur nichtinvasiven, prÀoperativen Dickenbestimmung von melanomverdÀchtigen HautlÀsionen

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    In this dissertation, methods for the calibration of optical coherence tomography (OCT) systems and for the simulation of optoacoustic signals are presented. The key question here is whether a multimodal system consisting of OCT and optoacoustics is suitable for noninvasive, preoperative thickness determination of skin lesions suspected of melanoma and what conditions, if any, must be met for this purpose. Given the current state of the art, such a modality for melanoma diagnosis would be very enriching for dermatology. In addition to the definition of malignant melanoma, the most common diagnostic procedures in dermatology will be explained. The current approach to melanoma diagnostics shows that there is a lot of potential for improvement in order to be able to make diagnoses preoperatively in the future and to prevent unnecessary surgical interventions. The project in which this work was developed is briefly presented. It also discusses the physical principles needed to simulate and calibrate the multimodal system. The methods presented in chapters 6 and 7 for calibrating the OCT and for simulating the optoacoustic signals then build on these fundamentals. The general setup of OCT systems as well as of two specific OCT devices is explained. The methods then presented for geometric calibration and refractive index correction are essential for the thickness determination of structures in OCT images. In chapter 7 different methods are presented which are suitable for the simulation of optoacoustic signals. On the one hand, the solution of the direct problem, i.e. the creation of optoacoustic signals, is shown as well as the solution of the indirect problem, in which conclusions can be drawn about the initial pressure profile if optoacoustic signals are available. Furthermore, optoacoustic signals of simulated melanomas are generated and evaluated, which is also important for answering the key question. The results of this dissertation are discussed in detail at the end and an outlook is given on how the work on the multimodal system will continue.In der vorliegenden Dissertation werden Methoden zur Kalibrierung von Optischen KohĂ€renztomographie (OCT)-Systemen und zur Simulation von Optoakustiksignalen prĂ€sentiert. Die Kernfrage hierbei ist, ob ein multimodales System aus OCT und Optoakustik fĂŒr eine nichtinvasive, prĂ€operative Dickenbestimmung von melanomverdĂ€chtigen HautlĂ€sionen geeignet ist und welche Bedingungen hierfĂŒr gegebenenfalls erfĂŒllt werden mĂŒssen. Beim derzeitigen Stand der Technik wĂ€re solch eine ModalitĂ€t fĂŒr die Melanomdiagnostik sehr bereichernd f š ur die Dermatologie. Neben der Definition eines malignen Melanoms werden die gelĂ€ufigsten diagnostischen Verfahren in der Dermatologie erlĂ€utert. Das momentane Vorgehen bei der Melanomdiagnostik zeigt, dass hier sehr viel Potenzial fĂŒr Verbesserungen ist, um zukĂŒnftig Diagnosen prĂ€operativ vornehmen und unnötige operative Eingriffe verhindern zu können. Es wird kurz das Projekt vorgestellt, in dem diese Arbeit entstanden ist. Außerdem werden die physikalischen Grundlagen erörtert, die fĂŒr die Simulation und Kalibrierung des multimodalen Systems benötigt werden. Auf diesen Grundlagen bauen dann die in Kapitel 6 und 7 vorgestellten Methoden zur Kalibrierung des OCT sowie zur Simulation der optoakustischen Signale auf. Es wird der allgemeine Aufbau von OCT-Systemen sowie von zwei speziellen OCT-GerĂ€ten erklĂ€rt. Die dann vorgestellten Methoden zur geometrischen Kalibrierung und zur Brechungsindexkorrektur sind unerlĂ€sslich fĂŒr eine Dickenbestimmung von Strukturen in OCT-Bildern. In Kapitel 7 werden verschiedene Verfahren vorgestellt, die sich zur Simulation von optoakustischen Signalen eignen. Hier wird zum einen die Lösung des direkten Problems, also das Erzeugen von Optoakustiksignalen gezeigt sowie die Lösung des indirekten Problems, bei der RĂŒckschluss auf das initiale Druckprofil geschlossen werden kann, wenn Optoakustiksignale vorliegen. Weiterhin werden Optoakustiksignale von simulierten Melanomen erzeugt und ausgewertet, was ebenfalls wichtig fĂŒr die Beantwortung der Kernfrage ist. Die Ergebnisse dieser Dissertation werden zum Schluss ausfĂŒhrlich erörtert und es wird ein Ausblick darauf gegeben, wie die Arbeit am multimodalen System weitergeht

    Strain and interfacial engineering of 2D materials

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    Deformable device technology with advanced functionalities spanning from wearable/personal electronics to flexible bio-implantable sensors, which require both static performance stability and dynamic sensitivity, has been ever-evolving with the substantial development in the field of two-dimensional (2D) materials. 2D materials are atomically thin, layered crystalline materials that possess strong intralayer (in-plane) covalent bond and weak interlayer (out-of-plane) van der Waals interaction resulting in extraordinary properties including high mechanical strength (in-plane) and extremely low bending stiffness (out-of-plane). Distinct from 3D bulk materials, the reduced dimensionality and the spatial confinement of 2D materials result in unique characteristics such as excellent electrical transport behavior, strong light-matter interaction, and vanishing flexural rigidity at the ultimate thickness limit, which will permit the achievement of next-generation flexible electronics beyond the capability of conventional semiconductor technology. Therefore, 2D materials have demanded substantial attention from the scientific community for both fundamental quantum physics/mechanics and device-level applications. Because of the exceptional mechanical strength and intrinsic flexibility, however, 2D materials can be strongly affected by external influences. Mechanical deformations, especially out-of-plane deformation, are commonly observed with 2D materials-based systems in the forms of intrinsic corrugation, wrinkles, delaminated buckles or crumples, and other non-linear complex deformations in an uncontrolled manner, which have been considered as inevitable topological defects. Furthermore, due to weak interlayer interactions of 2D materials via van der Waals interactions with surrounding environments, structural instability of delamination at the interfaces between 2D materials and substrate surfaces can occur. These mechanical instabilities are often considered as parameters deteriorating the mechanical integrity and functional performances of 2D materials-based systems. Contrary to such conventional wisdom, I have sought ways to leverage mechanical instabilities of 2D materials to advance functionalities of 2D materials-based systems including electrical sustainability, excitonic characteristics, energy generation, and novel optoelectronic phenomena by manipulating interfacial characteristics (interfacial engineering) and mechanical deformation (strain-engineering) of the constituent 2D material layers. First, I discussed a readily adaptable approach of inserting 2D materials to thin-film metal based flexible electrodes (2D-interfacial engineering) where we achieved several orders-of-magnitude enhanced strain resilient electrical functionality (which we termed ‘electrical ductility’) by manipulating mechanical fracture behaviors of thin-film metals from rapid straight cracking to progressive tortuous cracking via a buckle-guided fracture mechanism induced by 2D materials at the interface. I demonstrated that our 2D-interfacial engineering is not limited to a certain combination of metals and 2D materials, which can be incorporated into the existing flexible/wearable electronics applications. Next, I demonstrated how the wrinkling deformation of artificially stacked 2D materials via strain engineering affects the optical characteristics of interlayer excitons in heterobilayer system where the effect of mechanical strain remains relatively uncharacterized. We observed highly strain-tunable interlayer excitons with non-monotonic photoluminescence characteristics in MoS2/WSe2 heterobilayer. I further provided an insight on the competition between in-plane strain and out-of-plane interlayer coupling effects on the photoluminescence characteristics, which can be an additional tuning knob to manipulate excitonic behaviors in 2D-multilayered systems. As an extension of the strain effect on the heterobilayer system, I explored how crumpling deformation of 2D materials affects both mechanical (the effective stiffness) and electromechanical (piezoelectricity) properties. Our results suggest that the effective elastic modulus can be reduced for the controlled crumpled heterostructure where the effective modulus decreased as the aspect ratio of formed crumples decreased. I further demonstrated that the crumpled MoS2/graphene heterostructures can be utilized as an effective active layer for mechanical-to-electrical energy conversion under both instantaneous and continuous strain-driven modes of stretching, bending, acoustic and mechanical vibrations. Finally, I introduced a strain-control platform to create freestanding wrinkled structures of monolayer 2D materials for the first time, offering exciting opportunities to further investigate the fundamental strain-tunability of various materials properties in 2D materials. In particular, I showed the spatial modulation of photo-induced force (near-field dipole-dipole interactions) in freestanding wrinkled 2D materials, which we attributed to a combination of the in-plane strain-induced piezoelectric effect and the out-of-plane strain gradient-induced flexoelectric effect. In conclusion, I demonstrated that controlling the mechanical deformation of 2D materials permits emergent functionalities ranging from the nanoscale to macroscale including electrical ductility, controllable excitonic behaviors, and even energy generation. Furthermore, since the deformation of 2D materials can directly manipulate bond length and angle in the atomic lattice, deformation can tune the electronic structure and interfacial characteristics. Thus, strain and interfacial engineering can serve as effective strategies to explore advanced functionalities of 2D materials. I believe our approaches to manipulate interfacial characteristics and deformation of 2D materials-based systems, as well as in a freestanding form, contribute to the larger research community by opening up exciting opportunities to study fundamental strain physics and to advance multifunctional deformable device technologies including robust flexible electronics, novel excitonic sensors, and self-powering wearable/implantable devices for health and structural monitoring.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste

    Initiation of piezoelectricity expands the photocatalytic H2 production and decomposition of organic dye through g-C3N4/Ag/ZnO tri-components

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    The enhancement of photocatalytic reactivity through the internal electric field has received much attention. The combination of the piezoelectric effect and the photo-exiting process facilitates the segregation of the photogenerated carriers, thereby boosting the piezo-photocatalytic activity. We have constructed g-C3N4/Ag/ZnO tri-component composites; with various g-C3N4 precursors to achieve reliable photo/piezo-photocatalysis for H2 production and Rhodamine B (RhB) dye degradation. We observed that urea-based g-C3N4/Ag/ZnO (UCAZ) tri-components exhibit a superior H2 production rate of 1125.5 Όmol h−1 g−1 under photocatalytic conditions. When piezoelectric-potential was introduced into the photocatalysis reaction via ultrasonic, the H2 rate increased dramatically to 1637.5 Όmol h−1 g−1, which is approximately 145% greater than that light irradiation alone.Similarly, the catalytic decomposition ratio of Rhodamine B (RhB) under the coexistence of ultrasound and light, and degradation efficiency reached 99% in 120 min, which is higher than the value of (42%, 0.0031 min−1) for piezo-catalysis and (80%, 0.01 min−1) for photocatalysis condition alone. The rate constant under synergistic simulation reaches 0.021 min−1, which is 200% and 645% times higher than the sole light and ultrasonic illumination. Additionally, RhB degradation of all the tri-components was performed under solar light (Sunlight) and ultrasound irradiation, and efficiency reached 99.5% in 45 min with a rate constant of 0.06 min−1, which is 300% higher than the piezo-photocatalytic under LED source. The enhanced performance of the g-C3N4/Ag/ZnO tricomponent is attributed to the high specific surface area (168 m2 g−1) and synergetic effect of piezo catalysis and photocatalysis
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