116 research outputs found

    Polypyrrole (PPy) Coated Patterned Vertical Carbon Nanotube (pvCNT) Dry ECG Electrode Integrated with a Novel Wireless Resistive Analog Passive (WRAP) ECG Sensor

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    Polypyrrole (PPy) Coated Patterned Vertical Carbon Nanotube (pvCNT) Dry ECG Electrode Integrated with a Novel Wireless Resistive Analog Passive (WRAP) ECG Senso

    Protocol for fabricating electroless nickel immersion gold strain sensors on nitrile butadiene rubber gloves for wearable electronics

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    This protocol describes the fabrication of patterned conductive gold films on nitrile butadiene rubber (NBR) gloves for wearable strain sensors using electroless nickel immersion gold (ENIG) plating, a solution-based metallization technique. The resulting NBR/ENIG films are strain sensitive; resistance measurements of a patterned sensing array can be used to map human hand motions. This protocol also describes challenges related to the ENIG process and troubleshooting steps to achieve conformal gold films for strain sensing over a large working range. For complete details on the use and execution of this protocol, please refer to Mechael et al. (2021)

    Ready-to-wear strain sensing gloves for human motion sensing

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    Integrating soft sensors with wearable platforms is critical for sensor-based human augmentation, yet the fabrication of wearable sensors integrated into ready-to-wear platforms remains underdeveloped. Disposable gloves are an ideal substrate for wearable sensors that map hand-specific gestures. Here, we use solution-based metallization to prepare resistive sensing arrays directly on off-the-shelf nitrile butadiene rubber (NBR) gloves. The NBR glove acts as the wearable platform while its surface roughness enhances the sensitivity of the overlying sensing array. The NBR sensors have a sheet resistance of 3.1 ± 0.6 Ω/sq and a large linear working range (two linear regions ≤70%). When stretched, the rough NBR substrate facilitates microcrack formation in the overlying metal, enabling high gauge factors (62 up to 40% strain, 246 from 45 - 70% strain) that are unprecedented for metal film sensors. We apply the sensing array to dynamically monitor gestures for gesture differentiation and robotic control

    Rational Design of Flexible and Stretchable Electronics based on 3D Printing

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    Flexible and stretchable electronics have been considered as the key component for the next generation of flexible devices. There are many approaches to prepare the devices, such as dip coating, spin coating, Mayer bar coating, filtration and transfer, and printing, etc. The effectiveness of these methods has been proven, but some drawbacks cannot be ignored, such as lacking pattern control, labor consuming, requiring complex pretreatment, wasting conductive materials, etc. In this investigation, we propose to adopt 3D printing technology to design flexible and stretchable electronics. The objective is to rationally design flexible and stretchable sensors, simplify the preparation process, form the sample with the complex desirable patterns, and promote the performance of the samples. The dissertation comprises of three major parts: water-induced polymer swelling and its application in soft electronics, utilizing 3D printing to transfer conductive layer into elastomer for building soft electronics, and 3D printing of functional devices. In the first part, we developed the soft electronics with wrinkled structure via 3D printing and water-induced polymer swelling, which can avoid some disadvantages in conventional method, e.g., pre-stretching and organic solvent-induced polymer swelling, including mechanical loss, negative effect to human health, and unidirectionally response to external deformation. Water-induced polymer swelling was achieved by introducing soluble particles into silicone matrixes and soaking the polymer composites in aqueous solution. We have investigated the characteristics and mechanisms of water-induced polymer swelling. Then, the conductive materials were deposited on the swollen sample to form the desired wrinkled structures for stretchable sensors. Furthermore, a dopamine layer was adopted to enhance the adhesion of matrix and conductive layer. The improvement was a key enabler to achieve superior electrical properties of 3D printed stretchable sensors for long-term cyclic stretching. We have demonstrated a series of human motion detection by using these stretchable strain sensors. Another part is designing flexible electrodes with desirable complex pattern by transferring a conductive layer into soft substrates during a 3D printing process. Taking advantage of extrusion pressure and polymer adhesion, the thin conductive layers were embedded into the printed polymer patterns, which can achieve conductive flexible electronics with desirable complex patterns. High-quality transfer has been achieved through adjusting conductive layer thickness, nozzle-to-substrate distance, and printing parameters, etc. Moreover, various printing patterns were created, and their properties were exhibited. The stretchable sensors showed an outstanding stress-strain relationship and electrical response to external deformations. The third part is about 3D printing of functional devices. In the collaborated study, the drug particles were introduced into silicone matrix to prepare the drug-eluting devices. When water molecules transported into the silicone matrix, the loaded drug particles decomposed and released nitric oxide (NO) enabling antibacterial properties. It is noted that 3D printing is creatively employed to form the desirable patterns. We also observed a self-wiring effect in the printing process, i.e., the printed device is covered by a drug-free layer due to the diffusion of a low viscosity silicone component during printing, which can be utilized to prevent drug release bursts and to form a gradient drug-loaded device. The printed samples showed a sustainable NO release and good antibacterial property. Furthermore, the water-induced polymer swelling was possible to be used as actuator in humidity environment. There are some highlights deserving emphasis in the dissertation. Firstly, the water-induced polymer swelling is proposed to develop the flexible and stretchable electronics. The findings have a wide potential application. Additionally, a drug-eluting polymer device with a drug-loaded bulk and a drug-free coating is prepared via leveraging self-wiring effect in 3D printing. The structure can regulate the drug release rate. On the other hand, the additive manufacturing platform offers unique opportunities to produce drug-eluting silicone devices in a customized manner. Finally, 3D printing is employed to encapsulate the conductive layers to achieve the flexible electronics with patterned structure and high performances. The facile and effective approach provides a distinctive view in advancing the development of stretchable electronics

    Graphene textile smart clothing for wearable cardiac monitoring

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    Wearable electronics is a rapidly growing field that recently started to introduce successful commercial products into the consumer electronics market. Employment of biopotential signals in wearable systems as either biofeedbacks or control commands are expected to revolutionize many technologies including point of care health monitoring systems, rehabilitation devices, human–computer/machine interfaces (HCI/HMIs), and brain–computer interfaces (BCIs). Since electrodes are regarded as a decisive part of such products, they have been studied for almost a decade now, resulting in the emergence of textile electrodes. This study reports on the synthesis and application of graphene nanotextiles for the development of wearable electrocardiography (ECG) sensors for personalized health monitoring applications. In this study, we show for the first time that the electrocardiogram was successfully obtained with graphene textiles placed on a single arm. The use of only one elastic armband, and an “all-textile-approach” facilitates seamless heart monitoring with maximum comfort to the wearer. The functionality of graphene textiles produced using dip coating and stencil printing techniques has been demonstrated by the non-invasive measurement of ECG signals, up to 98% excellent correlation with conventional pre-gelled, wet, silver/silver-chloride (Ag / AgCl) electrodes. Heart rate have been successfully determined with ECG signals obtained in different situations. The system-level integration and holistic design approach presented here will be effective for developing the latest technology in wearable heart monitoring devices

    Development, fabrication and evaluation of textile electrodes for EDA measurements

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    In this study, textile-based dry electrodes that are integrable to clothing were developed, and their potential and limitations in EDA measurements were characterized. Copper-based and silver-based fabric electrodes and two types of electrodes embroidered from conductive thread were tested for EDA-measurements from fingers, and their performance was compared to that of commercial Ag/AgCl electrodes. Based on the experiment results, stimulus response of skin conductance could be measured with all the electrodes. Copper-based fabric and densely embroider silver electrodes give the best EDA response, which is comparable to that of commercial Ag/AgCl electrodes. The next step is to integrate these textile electrodes into gloves and socks and carry out EDA measurements on female and male adults as well as on children. Our goal is that these EDA measurement clothes would become a part of our everyday life, which would enable versatile health and well-being related applications.acceptedVersionPeer reviewe

    Smart Clothing Framework for Health Monitoring Applications

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    Wearable technologies are making a significant impact on people’s way of living thanks to the advancements in mobile communication, internet of things (IoT), big data and artificial intelligence. Conventional wearable technologies present many challenges for the continuous monitoring of human health conditions due to their lack of flexibility and bulkiness in size. Recent development in e-textiles and the smart integration of miniature electronic devices into textiles have led to the emergence of smart clothing systems for remote health monitoring. A novel comprehensive framework of smart clothing systems for health monitoring is proposed in this paper. This framework provides design specifications, suitable sensors and textile materials for smart clothing (e.g., leggings) development. In addition, the proposed framework identifies techniques for empowering the seamless integration of sensors into textiles and suggests a development strategy for health diagnosis and prognosis through data collection, data processing and decision making. The conceptual technical specification of smart clothing is also formulated and presented. The detailed development of this framework is presented in this paper with selected examples. The key challenges in popularizing smart clothing and opportunities of future development in diverse application areas such as healthcare, sports and athletics and fashion are discussed

    Exploring the Sonication Behaviours of Liquid Metals

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    Liquid metals are a class of materials that melt below or at near room temperature. Among the family of liquid metals, gallium and gallium-based alloys exhibit extraordinary functional features including metallic electrical and thermal characteristics, reactive surfaces rich in free ions and electrons, fluidity, and a tuneable oxide layer. Besides the exploration of the bulk of liquid metals, the mechanical synthesis of micron and nano-sized droplets is increasingly reported. Droplets of liquid metals, with increased surface-to-volume ratio, are increasingly shaped and dispersed utilising the sonication technique as a simple and straightforward method. The sonication process also briefly exposes the liquid metal surfaces to potential chemical and physical alterations. However, the sonication behaviours of gallium and gallium-based alloys are yet to be fully explored and the possibility for functionalisation is left uncovered. In this thesis, the author presents three different sonication combination setups with multiple controlling factors and finely tuned sonication conditions for synthesising functional materials from liquid gallium and gallium-based alloys. In the first stage of this Ph.D. thesis, the author establishes a pathway for room temperature nitridation of a gallium alloy utilising the sonication technique for the formation of gallium nitride, an important functional gallium compound. The room temperature sonication process utilised gaseous nitrogen and nitrogen-containing surfactants as nitrogen precursors in aqueous environments. The performance of the obtained particles was investigated for the biosensing of proteins of bovine serum albumin of different concentrations across time intervals, with the lowest detection threshold of 0.001 μg/ml. In the next stage of this Ph.D. thesis, the author thoroughly demonstrates the synthesis and dispersion of liquid gallium micron-sized particles in a viscous organic reactant with minimised surface oxidation. The gallium dispersion was then reacted into a flexible polyurethane sponge composite with thermal and electrical conductivity, and also with strain-sensing capabilities. The mechanical, thermal and electrical properties of the composites were tuneable corresponding to the gallium content and dispersion. The pressure and temperature-dependent electrical resistivity were demonstrated from an electrical insulator state to a conductive behaviour with resistivity as low as 3.8 Ω m. In the final stage of this Ph.D. thesis, the author presents a straightforward pathway for the spontaneous synthesis of a full inorganic gallium-based liquid metal composite at room temperature. The micron-sized gallium particles synthesised via a low-energy sonication method were interconnected with inorganic manganese oxide nanostructures. By varying the manganese precursor concentrations and performing an annealing post-treatment, the morphologies and optoelectronic properties of the inorganic composites were finely controlled and demonstrated. Collectively, the studies presented in this Ph.D. research uncover novel pathways and mechanistic insights towards the sonication behaviours of liquid metals towards emerging and future applications

    Research status and prospect of graphene materials in aviation

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    Among various 2D materials, graphene has received extensive research attention in the past 2-30 years due to its fascinating properties. The discovery of graphene has provided a huge boost and a new dimension to materials research and nanotechnology. Many lightweight materials with good performance have been widely used in the aviation field, which has greatly promoted the development of military and civilian industries and promoted technological innovation. Based on the introduction of the structure and properties of graphene, this paper summarizes the application value of graphene in the aerospace field in three aspects: energy equipment, sensors, and composite materials used outside aircraft.Comment: (22 pages, 23 figures
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