Next-generation lightweight-designed structures shall be able to perform self-state assessment via integrated health monitoring systems. In this article a carbon nanotube-embedded polymeric thin film is applied via inkjet-printing to perform spatial strain sensing in conjunction with using electrical impedance tomography. To gain an advanced understanding of the thin film’s spatial strain sensitivity, the elastoresistivity matrix, a fourth-order tensor correlating the strain state of a conductor into its normalized change in resistivity state, is characterized. The Montgomery method is adopted to derive the planar resistivity coefficients of the thin film, and a digital image correlation system is used to measure the planar strains. A validation test suggests that the calculated determinant of the correlated change in anisotropic resistivity shows a fairly similar result to the measured isotropic EIT reconstruction results.
risks increase with aging and are worsened by the global obesity epidemic. [3] At the other end of the spectrum, athletes, and military service members that undergo intense physical training and recreational activities can suffer severe overuse injuries. [4] Therefore, the ability to accurately monitor the range, amplitude, and quality of bodily movements is critical for promoting behavioral changes that yield higher levels of activity, maintaining and enhancing personal wellness, improving functional performance, preventing debilitating musculoskeletal injuries, and facilitating active rehabilitation. Wearable sensors that measure parameters associated with physical activity and bodily motions have been regarded as an indispensable tool for assessing personal wellness. Among its ≈350 million users worldwide (in 2019), [5,6] mainstream commercialized wearables pack force transducers, gyroscopes, [7] accelerometers, [8] and magnetometers in a hardcase accessory, [9] such as watches or bracelets, [10-12] to record vital signs (e.g., heart rate, respiration rate, peripheral oxygen saturation, and body temperature) and physical activity (e.g., steps). Despite their prevalence, they offer limited accuracy [13-15] , and their large, rigid, and bulky form factors can cause user discomfort or inconvenience, especially for the elderly. Recent advances in flexible sensors allow them to be worn at locations where traditional devices would otherwise be unsuitable or challenging because of their limited stretch-ability. [16] One approach is to integrate soft and flexible elastomeric sensors with fabric to monitor vitals and physiological parameters, [17] garments to measure hip, knee, and ankle kinematics, [18] and gloves to monitor finger motion, pressure, and tensile forces. [19] However, movement-and motion-induced strains in skin may not be effectively nor accurately measured by garment-based sensors due to poor strain transfer. An alternative is to use high-performance, stretchable, elastomeric strain sensors [20] (e.g., using nanomaterials including silver nanoparticles [21] or aligned single-walled carbon nanotubes [22]) mounted directly onto skin. In particular, graphene possesses extraordinary mechanical, thermal, and electrical properties, [23] and many sensors based on graphene exhibit superior sensing performance thanks to their topology-dependent, strain-sensitive, electromechanical properties. [24-26] For instance, a pulse monitor formed by integrating a crisscross graphene Wearable sensors that measure parameters associated with physical activity and bodily motions have been regarded as an indispensable tool for assessing personal wellness. Recent advances in nanocomposite strain sensors have been successfully used for monitoring skin strains and other strain-derived physiological parameters. This study complements the existing body of work and presents a flexible, self-adhering, fabric-based wearable sensor for measuring skin strains and human motions. Graphene nanosheet thin films are directly spray-coated on...
Fiber-reinforced polymer composites are a popular alternative to traditional metal alloys. However, their internally occurring damage modes call for strategies to monitor these structures. Multi-walled carbon nanotube-based polyelectrolyte thin films were manufactured using a layer-by-layer deposition methodology. The thin films were applied directly to the surface of glass fiber-reinforced polymer composites, with the purpose of structural monitoring. This work focuses on characterizing the sensitivity of the electrical properties of the film using time-and frequency domain methods under applied quasi-static and dynamic mechanical loading. In addition, environmental effects such as temperature and humidity are varied to characterize the sensitivity of the electrical properties due to these phenomena.
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