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...
Nanoassemblies of nanostructures on flexible substrates are important for fundamental study and applications. However, current methods to produce nanoassemblies usually are time-consuming, are complicated, and involve toxic and expensive chemicals. Here we demonstrate an effective one-step fabrication of flexible silver (Ag) nanoparticle based microplasma-engineered nanoassemblies (AgMENs) on cellulose papers using a unique microplasma-induced electrochemical method. The as-fabricated AgMENs show exceptional plasmonic properties for surface-enhanced Raman scattering (SERS) detection and catalytic ability for nitrophenol reduction. Ag nanoparticles (NPs) with crystalline-twinned nanostructures can be synthesized and deposited on cellulose papers in one step with ambient condition using microplasmas, providing enhanced charge transportation during Raman scattering. Three-dimensional (3D) confocal micro-Raman scattering study shows that a large SERS volume was formed in the as-fabricated AgMENs, achieving detection limits down to picomolar (10–12 M) and nanomolar (10–9 M) concentrations for rhodamine 6G (R6G) and folic acid (FA), respectively. The catalytic reduction of 4-nitrophenol (4-NP) of AgMENs was observed to have a pseudo-first-order rate constant of 1.13 min–1 and a low apparent activation energy of 4.6 kJ/mol for AgMENs. Our work opens an avenue of a scalable fabrication of flexible metal nanoparticle based substrates under ambient conditions for fundamental study and emerging applications including catalysis, sustainable energy, and biomedical imaging.
Stretchable surface-enhanced Raman scattering (SERS)active metal−organic nanocomposites with exceptional optical, mechanical, and electrical properties have attracted a lot of attention for emerging applications such as wearable devices, smart energy storage, and point-ofcare (POC) personal sensing. However, the current fabrication of SERSactive metal−organic nanocomposites usually involves time-consuming procedures, expensive and toxic chemicals, and harsh conditions such as high temperature, vacuum conditions, and strong acid−base reactions. Here, we developed a simple, low-cost, and environmentally friendly fabrication of stretchable porous poly(styrene−butadiene−styrene) (SBS)-based metal−organic nanocomposites with exceptional SERS enhancement and mechanical stability using a scalable and easy-tooperate microplasma engineering under ambient conditions. SERS-active polyhedral silver nanoparticles (polyAgNPs) with enormous localized electromagnetic field-induced hot spots can be synthesized and deposited on the elastic SBS fiber-based porous substrates with high density and uniformity by the plasma synthesis. The plasma-engineered polyAgNP-SBS nanocomposites show outstanding SERS enhancement factor (EF), low detection limit and wide detection range for SERS-based detection of cancer biomarkers. Our work provides a step for scalable and controlled engineering for stretchable metal−organic nanocomposites and an understanding of SERS properties of plasmonic nanostructures used for emerging applications such as optoelectronics, biomedical sensing, and clean energy.
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