IoT-Based Smart Health Monitoring System for COVID-19.

With the commencement of the COVID-19 pandemic, social distancing and quarantine are becoming essential practices in the world. IoT health monitoring systems prevent frequent visits to doctors and meetings between patients and medical professionals. However, many individuals require regular health monitoring and observation through medical staff. In this proposed work, we have taken advantage of the technology to make patients life easier for earlier diagnosis and treatment. A smart health monitoring system is being developed using Internet of Things (IoT) technology which is capable of monitoring blood pressure, heart rate, oxygen level, and temperature of a person. This system is helpful for rural areas or villages where nearby clinics can be in touch with city hospitals about their patient health conditions. However, if any changes occur in a patient's health based on standard values, then the IoT system will alert the physician or doctor accordingly. The maximum relative error (%ϵ r) in the measurement of heart rate, patient body temperature and SPO2 was found to be 2.89%, 3.03%, 1.05%, respectively, which was comparable to the commercials health monitoring system. This health monitoring system based on IoT helps out doctors to collect real-time data effortlessly. The availability of high-speed internet allows the system to monitor the parameters at regular intervals. Furthermore, the cloud platform allows data storage so that previous measurements could be retrieved in the near future. This system would help in identifying and early treatment of COVID-19 individual patients.

Tight-binding investigation of the structural and vibrational properties of graphene-single wall carbon nanotube junctions.

Hybrid carbon nanostructures based on single walled carbon nanotubes (SWNTs) and single layer graphene (SLG) have drawn much attention lately for their applications in a range of efficient hybrid devices. A few recent studies, addressing the interaction behavior at the heterojunction, considered charge transfer between the constituents (SWNTs and SLG) to be responsible for changes in the electronic and vibrational properties of their hybrid system. We report the effect of various factors, arising due to the interactions between the atoms of SWNTs and SLG, on the structural and vibrational properties of hybrid nanostructures investigated computationally within the framework of tight-binding DFT. These factors, such as the van der Waals (vdW) forces, structural deformation and charge transfer, are seen to affect the Raman active phonon frequencies of SWNTs and SLG in the hybrid nanostructure. These factors are already known to affect the vibrational properties of SWNTs and SLG separately and in this work, we have explored their role and interplay between these factors in hybrid systems. The contribution of different factors to the total shift observed in phonon frequencies is estimated and it is perceived from our findings that not only the charge transfer but the structural deformations and the vdW forces also affect the vibrational properties of components within the hybrid, with structural deformation being the leading factor. With decreasing separation between SWNTs and SLG, the charge transfer and the vdW forces both increase. However, the increase in vdW forces is relatively much higher and likely to be the main cause for larger Raman shifts observed at smaller separations.

A tight-binding study of the electron transport through single-walled carbon nanotube-graphene hybrid nanostructures.

Hybrid carbon nanostructures based on the sp2 hybridized allotropes of carbon, such as graphene and single-walled carbon nanotubes (SWCNTs), hold vast potential for applications in electronics of various forms. Electronic properties of such hybrid structures are modified due to the interaction between atoms of the components, which can be utilized to tailor the properties of the hybrid structures to suite the application. In this study, we have explored charge (electron) transport through the hybrid structures of single-layer graphene (SLG) and SWCNTs (both metallic and semiconducting) using the nonequilibrium Green's function formalism within the framework of tight-binding density functional theory. Our calculations show that the electronic transport in hybrid nanostructures is affected by the interactions between SWCNT and SLG in comparison to the individual components. The changes in the electronic structure and the transport properties with increasing interaction in hybrids (captured by decreasing the separation between SWCNT and SLG) are discussed, and it is demonstrated from this analysis that the hybrids with semiconducting SWCNTs and metallic SWCNTs show different behavior in the low bias regime while they show similar behavior at higher biases. The difference in the transport properties of hybrids with semiconducting and metallic SWCNTs is explained in terms of changes in the electronic structure, the local density of states, and the energy dispersion for electrons due to the interaction between atoms of the two components.

First principles prediction of amorphous phases using evolutionary algorithms.

We discuss the efficacy of evolutionary method for the purpose of structural analysis of amorphous solids. At present, ab initio molecular dynamics (MD) based melt-quench technique is used and this deterministic approach has proven to be successful to study amorphous materials. We show that a stochastic approach motivated by Darwinian evolution can also be used to simulate amorphous structures. Applying this method, in conjunction with density functional theory based electronic, ionic and cell relaxation, we re-investigate two well known amorphous semiconductors, namely silicon and indium gallium zinc oxide. We find that characteristic structural parameters like average bond length and bond angle are within ∼2% of those reported by ab initio MD calculations and experimental studies.

Fano lineshape and phonon softening in single isolated metallic carbon nanotubes.

Evolution of G-band modes of single metallic carbon nanotubes with the Fermi level shift is examined by simultaneous Raman and electron transport studies. Narrow Lorentzian line shape and upshifted frequencies are observed near the van Hove singularities. However, all G modes soften and broaden at the band crossing point. The concurrent appearance of an asymmetric Fano line shape at this point indicates that phonon-continuum coupling is intrinsic to single metallic tubes. The apparent Lorentzian line shapes of as-synthesized metallic tubes are induced by O2 adsorption causing the Fermi level shift.

Soft lithography using acryloxy perfluoropolyether composite stamps.

This paper describes composite patterning elements that use a commercially available acryloxy perfluoropolyether (a-PFPE) in various soft lithographic techniques, including microcontact printing, nanotransfer printing, phase-shift optical lithography, proximity field nanopatterning, molecular scale soft nanoimprinting, and solvent assisted micromolding. The a-PFPE material, which is similar to a methacryloxy PFPE (PFPE-DMA) reported recently, offers a combination of high modulus (10.5 MPa), low surface energy (18.5 mNm(-1)), chemical inertness, and resistance to solvent induced swelling that make it useful for producing high fidelity patterns with these soft lithographic methods. The results are comparable to, and in some cases even better than, those obtained with the more widely explored material, high modulus poly(dimethylsiloxane) (h-PDMS).

Insights on charge transfer doping and intrinsic phonon line shape of carbon nanotubes by simple polymer adsorption.

Doping of individual single-walled carbon nanotubes via noncovalent adsorption of polyethylenimine which converts p-type semiconducting nanotubes into n-type is examined by micro-Raman studies. Distinctively different responses are observed in metallic and in semiconducting nanotubes. Very little or no changes in the radial breathing and the disorder modes are observed upon polymer adsorption on semiconducting carbon nanotubes indicating noncovalent nature of this process. Tangential G-band spectral downshift of up to approximately 10 cm(-)(1) without line broadening is observed for semiconducting tubes suggesting similar magnitude of electron transfer as commonly observed in electrochemical doping with alkali metals. Strong diameter dependence is also observed and can be explained by thermal ionization of charge carriers with activation barrier that scales as the energy gap of the semiconducting nanotubes. In contrast, metallic nanotubes exhibit very different behavior with significant line broadening of the G-band and concurrent enhancement of the disorder mode. In certain cases, initially symmetric Lorentzian line shapes of the G-band features with narrow line widths similar to semiconducting tubes are converted to a broad, asymmetric Breit-Wigner-Fano line shape. Implications on the effects of electron injection and the local chemical environment on the intrinsic line shape of isolated carbon nanotubes are discussed.

Organic nanodielectrics for low voltage carbon nanotube thin film transistors and complementary logic gates.

We report the implementation of three dimensionally cross-linked, organic nanodielectric multilayers as ultrathin gate dielectrics for a type of thin film transistor device that uses networks of single-walled carbon nanotubes as effective semiconductor thin films. Unipolar n- and p-channel devices are demonstrated by use of polymer coatings to control the behavior of the networks. Monolithically integrating these devices yields complementary logic gates. The organic multilayers provide exceptionally good gate dielectrics for these systems and allow for low voltage, low hysteresis operation. The excellent performance characteristics suggest that organic dielectrics of this general type could provide a promising path to SWNT-based thin film electronics.

Electronically selective chemical functionalization of carbon nanotubes: correlation between Raman spectral and electrical responses.

Single-walled carbon nanotubes (SWNTs) demonstrate remarkable electronic and mechanical properties useful in developing areas such as nanoelectromechanical systems and flexible electronics. However, the highly inhomogeneous electronic distribution arising from different diameters and chirality in any given as-synthesized SWNT samples imposes severe limitations. Recently demonstrated selective chemical functionalization methods may provide a simple scalable means of eliminating metallic tubes from SWNT transistors and electronic devices. Here, we report on combined electron transport and Raman studies on the reaction of 4-bromobenzene diazonium tetrafluoroborate directly with single and networks of SWNT transistors. First, Raman studies are carried out on isolated individual SWNTs grown on SiO2/Si substrates by chemical vapor deposition with and without metal contacts. Metallic tubes are found to have, on average, higher reactivity toward diazonium reagents. However, a considerable degradation of electrical properties of semiconducting tubes occurs if the reaction is carried out to the point where the conductivity of metallic tubes is significantly suppressed. Insights from single-tube studies are then applied to elucidate the electrical and the Raman responses of SWNT random network transistors of different channel lengths to chemical functionalization.

Polymer electrolyte gating of carbon nanotube network transistors.

Network behavior in single-walled carbon nanotubes (SWNTs) is examined by polymer electrolyte gating. High gate efficiencies, low voltage operation, and the absence of hysteresis in polymer electrolyte gating lead to a convenient and effective method of analyzing transport in SWNT networks. Furthermore, the ability to control carrier type with chemical groups of the host polymer allows us to examine both electron and hole conduction. Comparison to back gate measurements is made on channel length scaling. Frequency measurements are also made giving an upper limit of approximately 300 Hz switching speed for poly(ethylene oxide)/LiClO(4) gated SWNT thin film transistors.

Guided growth of large-scale, horizontally aligned arrays of single-walled carbon nanotubes and their use in thin-film transistors.

A convenient process for generating large-scale, horizontally aligned arrays of pristine, single-walled carbon nanotubes (SWNTs) is described. The approach uses guided growth, by chemical vapor deposition (CVD), of SWNTs on miscut single-crystal quartz substrates. Studies of the growth reveal important relationships between the density and alignment of the tubes, the CVD conditions, and the morphology of the quartz. Electrodes and dielectrics patterned on top of these arrays yield thin-film transistors that use the SWNTs as effective thin-film semiconductors. The ability to build high-performance devices of this type suggests significant promise for large-scale aligned arrays of SWNTs in electronics, sensors, and other applications.