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The proliferation of IoT devices comes with many challenges among which security is one of the most serious issues. In order to address the security issue for low-end IoT devices, ARM recently proposed the Platform Security Architecture (PSA), which provides execution isolation to safely manage and protect the computing resources of low-end IoT devices. However, developers implementing IoT services for PSA-based IoT devices need to follow complex development procedures and understand the PSA hardware, which dramatically increases the development time and cost of PSA-based IoT devices. This paper analyzes vulnerabilities that may arise from general purpose low-end IoT devices to derive the security requirements and essential security services for PSA-based IoT devices, and proposes a secure platform model based on the analysis results. The proposed secure platform model consists of system security services and application security services based on the basic PSA model and essential trusted sub-systems, and it is designed to be flexible and applicable to various types of PSA-based IoT devices. In addition, it provides secure platform services APIs to enable easy and fast development of IoT services. To evaluate the proposed secure platform model, two proof-of-concept implementations are provided by using both the basic PSA model with Secure Element (SE) and a reference device for ARM’s PSA. Finally, a case study shows that the development of IoT services can be done easily and quickly using the proposed security platform model.

Carboxylated single-walled carbon nanotubes (SWCNT–COOH) have long been studied for gas/vapor sensing. Controlling the pH during the carboxylation process by adding an acid or a base yields inks wi...

An all three-dimensional (3D)-printed flexible ZnO ultraviolet (UV) photodetector is demonstrated, where the 3D-printing method is used not only for the electrode and photosensitive material but also for creating a substrate. An ultraflat and flexible substrate capable of serving as the backbone layer is developed using a water-dissolvable polymer layer for surface planarization. A two-layered printing followed by surface treatment is demonstrated for the substrate preparation. As mechanical support but flexible, a thick and sparse thermoplastic polyurethane layer is printed. On its surface, a thin and dense poly(vinyl alcohol) (PVA) is then printed. A precise control of PVA reflow using a microwater droplet results in a flexible and extremely uniform substrate. A Cu-Ag nanowire network is directly 3D printed on the flexible substrate for the conducting layer, followed by ZnO for the photosensitive material. Unlike the planar two-dimensional printing that provides thin films, 3D printing allows the electrode to have a step height, which can be made like a dam to accommodate a thick film of ZnO. Photosensitivity as a function of various ZnO thickness values was investigated to establish an optimal thickness for UV response. The device was also tested in natural sunlight along with stability and reliability.

An atmospheric pressure plasma based printer is described as an alternative to conventional techniques including inkjet printing. The approach is demonstrated to be capable of printing various nanomaterials, and adjusting the plasma parameters, carrier gas flows and the physical parameters of the inks or nanomaterial suspensions can optimize the print quality. Raman analysis was used to characterize the oxide materials and carbon nanotubes printed using this technique, revealing high quality prints. The printed carbon nanotubes were used in a gas sensor chip and shown to provide good ammonia detection capability.

Single-walled carbon nanotubes (SWCNTs) have long been advocated for the detection of various gases and vapors. Often, strategies to modify the nanotubes have been shown to be successful in eliciti...

The emerging Internet of things (IoT) demands not only new device technologies but also strengthening the security of things in order to prevent tampering and hacking. Humans have unique characteri...

Wireless body area network (WBAN) is a communication technology, which aims providing both medical and consumer electronics services through sensor devices in, on, or around a human body. Due to the absence of the IEEE 802.15.6-based RF modules, the IEEE 802.15.4, a typical low-power communication technology of which requirements are similar, is considered to implement WBANs. In the case where a lot of WBANs coexist, meanwhile, collisions and signal attenuations may lead to their communication performance degradation. However, the IEEE 802.15.4 does not provide any solutions to solve coexistence problems, and thus, coexistence mitigation schemes for the IEEE 802.15.4-based WBANs are necessary. In this paper, we perform preliminary experiments to identify aspects of coexistence problem among the coexisting IEEE 802.15.4-based WBANs. Based on the results of preliminary experiments, we also propose a hybrid channel access scheme to mitigate coexistence problems in WBANs. The proposed scheme can be classified into two phases. In the first phase, the proposed scheme provides probabilistic collision avoidance on the contention-free period. When the pre-defined requirements of reliability cannot be satisfied with performing the first phase, the proposed scheme performs the second phase, which helps to mitigate collision or interference through changing channel access method. To evaluate the performance of the proposed scheme, we implement our scheme and perform experiments by comparing with an IEEE 802.15.4-based WBAN.

With the recent advent of 360 cameras, spherical panorama images are becoming more popular and widely available. In a spherical panorama, alignment of the scene orientation to the image axes is important for providing comfortable and pleasant viewing experiences using VR headsets and traditional displays. This paper presents an automatic method for upright adjustment of 360 spherical panorama images without any prior information, such as depths and gyro sensor data. We take the Atlanta world assumption and use the horizontal and vertical lines in the scene to formulate a cost function for upright adjustment. In addition to fast optimization of the cost function, our method includes outlier handling to improve the robustness and accuracy of upright adjustment. Our method produces visually pleasing results for a variety of real-world spherical panoramas in less than a second, and the accuracy is verified using ground-truth data.

Thermotherapy is an effective method for pain relief, recovery from injury, and general healthcare. The ordinary heat pad used for thermotherapy at home is not usually tailored to the individual but supplied in a few different pre-fixed sizes and shapes for mass marketing. A customized wearable heat pad often requires expert support. Herein, an instant, custom-fit, and on-demand heat pad for thermotherapy is demonstrated. The heater is directly printed using silver nanoparticle ink on an off-the-shelf medical grade tape by inkjet technology. By coating the tape with silica nanoparticles as ink-absorbing layer and chloride ions as chemical sintering agent, stable heater patterns are printed without the need for subsequent high temperature sintering process. A 3D scanner is used to acquire body information, and a customized heater is produced using the information. The printed heat pad is attached to the shoulder and the effect of thermotherapy is verified objectively through electroencephalography and subjectively through survey. This printed heat pad produced by simple and low-cost fabrication provides wearable medical devices for personal thermotherapy.

A single walled carbon nanotube (SWCNT) based γ ray detector is demonstrated without a conventional scintillation mechanism. The change in the conductance of a two terminal SWCNT resistor in response to γ ray exposure is exploited as a sensing mechanism. Radiation-induced ambient oxygen dissociation and subsequent adsorption of oxygen species on the SWCNT surface alter its electrical properties. The responses to the total dose and dose rate are investigated along with the sensing mechanism. The detector showed good sensitivity to γ ray and a capability to distinguish radiation dose rates ranging from 2.4 to 16.4 R/min.

Profiling the transcriptomes of individual cells with single-cell RNA sequencing (scRNA-seq) has been widely applied to provide a detailed molecular characterization of cellular heterogeneity within a population of cells. Despite recent technological advances of scRNA-seq, technical variability of gene expression in scRNA-seq is still much higher than that in bulk RNA-seq. Accounting for technical variability is therefore a prerequisite for correctly analyzing single-cell data. This chapter describes a computational pipeline for detecting highly variable genes exhibiting higher cell-to-cell variability than expected by technical noise. The basic pipeline using the scater and scran R/Bioconductor packages includes deconvolution-based normalization, fitting the mean-variance trend, testing for nonzero biological variability, and visualization with highly variable genes. An outline of the underlying theory of detecting highly variable genes is also presented. We illustrate how the pipeline works by using two case studies, one from mouse embryonic stem cells with external RNA spike-ins, and the other from mouse dentate gyrus cells without spike-ins.

Profiling the transcriptomes of individual cells with single-cell RNA sequencing (scRNA-seq) has been widely applied to provide a detailed molecular characterization of cellular heterogeneity within a population of cells. Despite recent technological advances of scRNA-seq, technical variability of gene expression in scRNA-seq is still much higher than that in bulk RNA-seq. Accounting for technical variability is therefore a prerequisite for correctly analyzing single-cell data. This chapter describes a computational pipeline for detecting highly variable genes exhibiting higher cell-to-cell variability than expected by technical noise. The basic pipeline using the scater and scran R/Bioconductor packages includes deconvolution-based normalization, fitting the mean-variance trend, testing for nonzero biological variability, and visualization with highly variable genes. An outline of the underlying theory of detecting highly variable genes is also presented. We illustrate how the pipeline works by using two case studies, one from mouse embryonic stem cells with external RNA spike-ins, and the other from mouse dentate gyrus cells without spike-ins.

Recently, the significance of internet of things (IoT) is rapidly growing in the next generation of information and communication technology due to rapid advances in wireless communication technologies which have triggered the development of low-power, reliable and miniaturized devices. These advances lead to the creation of IoT ecosystem that enables development of various services. Especially, there are a number of attempts to apply communication technology of IoT in the field of healthcare services which deals with medical applications such as a remote medical treatment. In IoT-based healthcare system, in general, a number of medical devices are densely deployed in narrow area. Therefore, they are exposed to signal interference among them which causes significant performance degradation. In this paper, we present an Analytical Hierarchy Process (AHP)-based network interface and channel selection algorithm for multi-channel MAC protocols in IoT ecosystem that take into account a multitude of decision factors, such as expected channel condition, latency and frame reception ratio. The proposed scheme can provide flexibility for various requirements of different medical services through performing AHP. In particular, the proposed scheme considers IoT-based healthcare system because it is the most complex scenario of fundamental IoT applications. To evaluate the performance of the proposed algorithm, we perform extensive simulations, and the simulation study shows that the proposed algorithm provides low latency and high reliability.

A Wireless body area network (WBAN) is a communication network that provides both medical and consumer electronics services by using sensors in/on/around a human body. In general, a WBAN environment suffers from frequent link loss due to interferences among sensors scattered over a body. In addition, the channel condition can frequently change by postural body movement, which increases packet drops, retransmissions, and eventually power consumption. This paper presents an Analytical Hierarchy Process (AHP)-based flexible relay node selection scheme that considers a multitude of decision factors, such as average SNR, remaining energy ratio, and traffic load. Moreover, the proposed scheme can adaptively satisfy the requirements of WBAN in various scenarios. Our simulation study shows that the proposed method provides high communication reliability and low power consumption.

The denitrification of nitrate (NO3(-)) by mixed cultures in the presence of zero-valent iron [Fe(0)] and biochar was investigated through a series of batch experiments. It was hypothesized that biochar may provide microbes with additional electrons to enhance the anaerobic biotransformation of nitrate in the presence of Fe(0) by facilitating electron transfer. When compared to the anaerobic transformation of nitrate by microbes in the presence of Fe(0) alone, the presence of biochar significantly enhanced anaerobic denitrification by microbes with Fe(0). Graphite also promoted the anaerobic microbial transformation of nitrate with Fe(0), and it was speculated that electron-conducting graphene moieties were responsible for the improvement. The results obtained in this work suggest that nitrate can be effectively denitrified by microbes with Fe(0) and biochar in natural and engineered systems.

Successful transition to commercialization and practical implementation of nanotechnology innovations may very well need device designs that are tolerant to the inherent variations and imperfections in all nanomaterials including carbon nanotubes, graphene, and others. As an example, a single-walled carbon nanotube network based gas sensor is promising for a wide range of applications such as environment, industry, and biomedical and wearable devices due to its high sensitivity, fast response, and low power consumption. However, a long-standing issue has been the production of extremely high purity semiconducting nanotubes, thereby contributing to the delay in the market adoption of those sensors. Inclusion of even less than 0.1% of metallic nanotubes, which is inevitable, is found to result in a significant deterioration of sensor-to-sensor uniformity. Acknowledging the coexistence of metallic and semiconducting nanotubes as well as all other possible imperfections, we herein present a novel variation-tolerant sensor design where the sensor response is defined by a statistical Gaussian measure in contrast to a traditional deterministic approach. The single input and multiple output data are attained using multiport electrodes fabricated over a relatively large area single nanotube ensemble. The data processing protocol discards outlier data points and the origin of the outliers is investigated. Both the experimental demonstration and complementary analytical modeling support the hypothesis that the statistical analysis of the device can strengthen the credibility of the sensor constructed using nanomaterials with any imperfections. The proposed strategy can also be applied to physical, radiation, and biosensors as well as other electronic devices.

Carbon nanotube (CNT) is a promising candidate as a sensor material for the sensitive detection of gases/vapors, biomarkers, and even some radiation, as all these external variables affect the resistance and other properties of nanotubes, which forms the basis for sensing. Ultraviolet (UV) radiation does not impact the nanotube properties given the substantial mismatch of bandgaps and therefore, CNTs have never been considered for UV sensing, unlike the popular ZnO and other oxide nanwires. It is well-known that UV assists the adsorption/desorption characteristics of oxygen on carbon nanotubes, which changes the nanotube resistance. Here, we demonstrate a novel sensor structure encapsulated with an air pocket, where the confined air is responsible for the UV sensing mechanism and assures sensor stability and repeatability over time. In addition to the protection from any contamination, the air pocket encapsulated sensor offers negligible baseline drift and fast recovery compared to previously reported sensors. The air pocket isolated from the outside environment can act as a stationary oxygen reservoir, resulting in consistent sensor characteristics. Furthermore, this sensor can be used even in liquid environments.

A water-based conductive carbon nanotube (CNT) ink was synthesized with single-walled CNT and sodium dodecylbenezenesulfonate as surfactant. Direct writing on paper using this ink was demonstrated with off-the-shelf nib and cartridges in a fountain pen handwriting tool. It is lightweight and portable which allows writing on curved substrates. The through paper via was easily achieved by wetting method. Dual-side and multi-layer paper circuit boards were demonstrated by direct writing. The drawn pattern displays uniformity and reproducibility. The exceptional adhesion of CNT on cellulose paper shows good robustness against bending, folding, crumpling and other mechanical stress. A chemical sensor fabricated by direct writing showed good response down to 10 ppm of ammonia vapor in air.

A single-wall carbon nanotube (CNT) based ammonia sensor was implemented on cellulose paper. Two types of devices were fabricated and compared: CNT-on-paper and a CNT–cellulose composite. The resistance shift of the CNT network upon ammonia exposure was monitored in the chemiresistor approach. The CNT-on-paper showed faster response/recovery and higher sensitivity than the CNT–cellulose composite due to the larger reaction surface. Compared to the control sensor made on a glass substrate, the paper based sensor characteristics exhibited superior uniformity and repeatability. The present approach can be utilized for smart paper featuring low-cost disposable applications.

The use of printed electronics in conjunction with nanomaterials such as carbon nanotubes (CNTs) proves to be an effective means for simple, efficient and cost-effective chemical and bio sensing applications due to their high surface area to volume ratio and other attractive properties. However, successful commercial implementation of nanosensors has been elusive due to inconsistent performance across the sensors, which translates to decreased credibility and reproducibility. Furthermore, the process uniformity in printed electronics is inferior to solid-state microfabrication technology as printed sensors suffer from material and process-induced variability at the current level of maturity. In order to take advantage of the promise of nanotechnology driven sensors, we herein propose an array of chemiresistors formed on one substrate as a single input multiple output (SIMO) sensor. Then, individual responses from sub-sensors in a SIMO sensor are aggregated and result in a statistical mean response to overcome variability issues. Random sampling was performed in this work from a sufficiently large population of CNT-based sub-sensors to define a representative set whose behavior closely mimics a larger array. The convergence of the population mean is proven from randomly chosen samples beyond a certain number of sub-sensors. An optimal strategy including sensor layout and power consumption is provided based on the resulting data analysis.

Air quality monitoring in the crew cabin is important for crew health and safety. In the past, bulky instruments such as mass spectrometer have been used but simple sensors, which are small and consume low power can be used to get variation of gas concentrations across the cabin. Availability of such sensor chips would be useful for planetary exploration that involves mapping the atmosphere. We have been developing printed sensors that can be printed on demand using the future “ Fablab “ facilities being planned for the International Space Station. We use single-walled carbon nanotubes as the primary sensing material and use variations such as doping, functionalization etc. to incorporate multiple sensors in a sensor array. Since commercial nanomaterials lack consistency in quality, we have also developed a multielectrode system that gives N(N-1)/2 data points for N number of electrodes to provide a stochastic system instead of a single deterministic data point from a two-electrode system. This “ Single Input Multiple Output (SIMO)” system provides a better sensor-to-sensor variation and results for sensing CO2 and ammonia will be presented. This work was supported by the NASA In Space Manufacturing program.

The cognitive radio technology has been adopted as a promised solution to deal with overcrowded problem in ISM band. In wireless sensor networks, the cognitive radio technology enables sensor nodes to occupy licensed band in opportunistic manner and introduces advantages of improving spectrum utilization and increasing system throughput. By considering the opportunistic spectrum access nature, in this paper, we aim to provide a stable path selection scheme for cognitive radio sensor networks. The proposed routing protocol utilizes priori delivery information and derives a novel routing metric for the optimal path selection. The routing metric is derived from naïve Bayes inference and used to indicate the path stability by means of delivery probability. We show through extensive simulations that the proposed routing protocol is efficient to find the most probable delivery path and increase the system throughput.

Lead frames are generated in large quantities by modern semiconductor packaging industry and they contain significant concentrations of valuable tin, nickel, and copper. For electrowinning of tin from waste lead frames, hydrochloric acid leaching of tin is quite advantageous, but solution stability, electrolytic efficiency and deposit morphology should be optimized before commercialization. HCl electrolyte was diluted (distilled water: HCl = 350:150) for electrowinning of waste lead frames at 40 °C with 0.2 A/cm2 and Ti-Ir cathode. After 4 h electrowinning, 99% pure Sn with 99.1% recovery rate was produced. Therefore, aqueous HCl electrolyte was quite effective for electrowinning of Sn leaching solution, and a higher recovery rate of purer Sn within shorter electrowinning time was obtained.

The development of a tin oxide nanoparticle based sensor for detecting carbon monoxide at low temperature, 60 °C is presented. A combination of three approaches namely, (1) addition of a catalytic metal – 1.5% palladium, (2) optimization of organic binder content, and (3) a proper design of electrodes, leads to high sensitivity, excellent repeatability, and long-term stability in sensor response. The sensors have been tested in dry ( 70% RH) conditions, and no humidity effect on the sensor performance was noticed. The sensors using 15% hydroxypropyl cellulose (HPC) mixed with Pd/SnO2 show sensitivity to CO gas in the parts per million (ppm) level of concentration, 5–10% repeatability in 6–18 ppm CO exposures, and active response for more than 40 days. In addition, the fatigued sensors were recoverable with a brief heating process.

A Wireless Body Area Networks (WBAN) is a communication network that provides both medical and consumer electronics (CE) services by using sensor devices in, on, or around a human body. To provide reliable communication with low power consumption for in-body communication, the IEEE 802.15.6 provides Medical Implant Communication Service (MICS) band and defines its communication policy. However, MICS band communication suffer from the coexistence problem, which causes significant performance degradation due to high-density deployment and network-level mobility of WBANs. In addition, existing coexistence mitigation schemes in IEEE 802.15.6 do not consider the MICS band. To overcome the coexistence problem, numerous studies have been conducted for multi-channel usage in WBANs, but they just include simple channel selection schemes which do not provide reliable channel selection. This paper proposes an Adaptive Channel Estimation and Selection Scheme (ACESS) for coexistence mitigation in WBANs. The proposed method maintains a history table and predicts the conditions of available channels based on two-state Markov chain with an exponentially controlled channel history, which can control the sensitivity of prediction. Our simulation study show that the proposed scheme can improve communication performance in terms of Packet Reception Ratio (PRR) under coexistence environments with multiple WBANs.

A humidity sensor on cellulose paper is demonstrated using single-walled carbon nanotubes functionalized with carboxylic acid. The conductance shift of the nanotube network entangled on the microfibril cellulose is utilized for the humidity sensing. Compared to the control sensor made on a glass substrate, the cellulose-mediated charge transport on the paper substrate enhances the sensitivity. The sensor response exhibits linear behavior up to a relative humidity of 75% with good repeatability and low hysteresis. A simple circuit model is used to explain the sensor results. This approach is a step toward future paper electronics for low-cost disposable applications.

Wireless body area networks (WBANs) provide medical and/or consumer electronics (CE) services within the vicinity of a human body. In a WBAN environment, immediate and reliable data transmissions during an emergency situation should be supported for medical services. In this letter, we propose a flexible emergency handling scheme for WBAN MAC protocols. The proposed scheme can be applied to superframe-structured MAC protocols such as IEEE 802.15.4 and its extended versions. In addition, our scheme can be incorporated into the current working draft for IEEE 802.15.6 standards. Extensive simulations were performed and the low latency of emergent traffics was validated.

A Wireless Body Area Network (WBAN) which consists of wireless sensors in/on/around human body requires high reliability for medical data. The coexistence problem which occurs when multiple-WBANs occupy the same channel at the same time declines the performance of the network. It is an important issue because this problem causes the collision of data among WBANs. For that reason, the IEEE 802.15.6 which was established for WBAN standardization defined guidelines to solve this problem, but these guidelines did not provide detailed methods. To solve this problem, there are also a few related works by using graph coloring algorithm as a general theory to assign limited resources but they cannot satisfy the requirements of WBAN. In this paper, we propose a distributed multi-coloring algorithm to mitigate coexistence problems among WBANs. The proposed algorithm shows short transmission-cycle per WBAN through multiple coloring with a color sequence and the efficiency of the proposed scheme is verified by the numerical results which outperform existing works in multiple WBANs environment.

Two resorcinarene surfactants with sulfur-functionalized headgroups have been evaluated for their ability to stabilize dispersions of midnanometer (16−87 nm)-sized gold particles in organic solvents. Citrate-stabilized colloidal gold nanoparticles were extracted from aqueous solutions into toluene or chloroform by tetrabenzylthiol resorcinarene 1 or tetraarylthiol resorcinarene 2. The nanoparticle dispersions were subjected to various conditions and monitored for changes in plasmon absorption intensity. The stability of the dispersions was dependent on the chemisorptive properties of the surfactant headgroup, with tetrabenzylthiol 1 being the more effective dispersant. Nanoparticles encapsulated by 1 were also highly robust, demonstrated good resistance to alkanethiol-induced flocculation, and could be redispersed after repeated precipitations in polar solvents. Surface-enhanced Raman scattering analysis and X-ray photoelectron spectroscopic studies confirmed significant differences in the chemisorptive p...

PARC and NASA Ames have developed part-per-million level sensitivity room-temperature printed gas sensors based on arrays of modified single-walled carbon nanotubes (SWNTs). The SWNT sensors change resistance in response to reversible electro-chemical interactions between target analytes and the modifications on the SWNTs. The ultra-low power (microwatt level) ability to measure trace-gas concentrations through changes in SWNT resistance has enabled us to build an autonomous, off-the-grid, distributed gas sensing network to be deployed to the ARPA-E natural gas leak testing facility in Ft. Collins, CO during the spring of 2017. During this deployment, the leak detection network will be subjected to tests of its accuracy and precision in locating the sources of leaks on a mock natural gas well-pad. The key enablers of this technology are the SWNTs which we have modified with coatings, chemical functionalization, and nanoparticles, to achieve sensitivity to a wide selection of gases including CH4, NH3, CO, H2S, etc., in the presence of real-world environmental conditions. We will report on the results of this field deployment, along with a discussion of the SWNT modifications made to create the sensor arrays.