Crowdsensing IoT Architecture for Pervasive Air Quality and Exposome Monitoring: Design, Development, Calibration, and Long-Term Validation.

A pervasive assessment of air quality in an urban or mobile scenario is paramount for personal or city-wide exposure reduction action design and implementation. The capability to deploy a high-resolution hybrid network of regulatory grade and low-cost fixed and mobile devices is a primary enabler for the development of such knowledge, both as a primary source of information and for validating high-resolution air quality predictive models. The capability of real-time and cumulative personal exposure monitoring is also considered a primary driver for exposome monitoring and future predictive medicine approaches. Leveraging on chemical sensing, machine learning, and Internet of Things (IoT) expertise, we developed an integrated architecture capable of meeting the demanding requirements of this challenging problem. A detailed account of the design, development, and validation procedures is reported here, along with the results of a two-year field validation effort.

A Wearable Low-Power Sensing Platform for Environmental and Health Monitoring: The Convergence Project.

The low-power sensing platform proposed by the Convergence project is foreseen as a wireless, low-power and multifunctional wearable system empowered by energy-efficient technologies. This will allow meeting the strict demands of life-style and healthcare applications in terms of autonomy for quasi-continuous collection of data for early-detection strategies. The system is compatible with different kinds of sensors, able to monitor not only health indicators of individual person (physical activity, core body temperature and biomarkers) but also the environment with chemical composition of the ambient air (NOx, COx, NHx particles) returning meaningful information on his/her exposure to dangerous (safety) or pollutant agents. In this article, we introduce the specifications and the design of the low-power sensing platform and the different sensors developed in the project, with a particular focus on pollutant sensing capabilities and specifically on NO2 sensor based on graphene and CO sensor based on polyaniline ink.

Nanowire Tunnel FET with Simultaneously Reduced Subthermionic Subthreshold Swing and Off-Current due to Negative Capacitance and Voltage Pinning Effects.

Nanowire tunnel field-effect transistors (TFETs) have been proposed as the most advanced one-dimensional (1D) devices that break the thermionic 60 mV/decade of the subthreshold swing (SS) of metal oxide semiconductor field-effect transistors (MOSFETs) by using quantum mechanical band-to-band tunneling and excellent electrostatic control. Meanwhile, negative capacitance (NC) of ferroelectrics has been proposed as a promising performance booster of MOSFETs to bypass the aforementioned fundamental limit by exploiting the differential amplification of the gate voltage under certain conditions. We combine these two principles into a single structure, a negative capacitance heterostructure TFET, and experimentally demonstrate a double beneficial effect: (i) a super-steep SS value down to 10 mV/decade and an extended low slope region that is due to the NC effect and, (ii) a remarkable off-current reduction that is experimentally observed and explained for the first time by the effect of the ferroelectric dipoles, which set the surface potential in a slightly negative value and further blocks the source tunneling current in the off-state. State-of-the-art InAs/InGaAsSb/GaSb nanowire TFETs are employed as the baseline transistor and PZT and silicon-doped HfO2 as ferroelectric materials.

Effect of hysteretic and non-hysteretic negative capacitance on tunnel FETs DC performance.

This work experimentally demonstrates that the negative capacitance effect can be used to significantly improve the key figures of merit of tunnel field effect transistor (FET) switches. In the proposed approach, a matching condition is fulfilled between a trained-polycrystalline PZT capacitor and the tunnel FET (TFET) gate capacitance fabricated on a strained silicon-nanowire technology. We report a non-hysteretic switch configuration by combining a homojunction TFET and a negative capacitance effect booster, suitable for logic applications, for which the on-current is increased by a factor of 100, the transconductance by 2 orders of magnitude, and the low swing region is extended. The operation of a hysteretic negative capacitance TFET, when the matching condition for the negative capacitance is fulfilled only in a limited region of operation, is also reported and discussed. In this late case, a limited improvement in the device performance is observed. Overall, the paper demonstrates the main beneficial effects of negative capacitance on TFETs are the overdrive and transconductance amplification, which exactly address the most limiting performances of current TFETs.

Tunnel field-effect transistors as energy-efficient electronic switches.

Power dissipation is a fundamental problem for nanoelectronic circuits. Scaling the supply voltage reduces the energy needed for switching, but the field-effect transistors (FETs) in today's integrated circuits require at least 60 mV of gate voltage to increase the current by one order of magnitude at room temperature. Tunnel FETs avoid this limit by using quantum-mechanical band-to-band tunnelling, rather than thermal injection, to inject charge carriers into the device channel. Tunnel FETs based on ultrathin semiconducting films or nanowires could achieve a 100-fold power reduction over complementary metal-oxide-semiconductor (CMOS) transistors, so integrating tunnel FETs with CMOS technology could improve low-power integrated circuits.

Graphene Quantum Capacitors for High Frequency Tunable Analog Applications.

Graphene quantum capacitors (GQC) are demonstrated to be enablers of radio-frequency (RF) functions through voltage-tuning of their capacitance. We show that GQC complements MEMS and MOSFETs in terms of performance for high frequency analog applications and tunability. We propose a CMOS compatible fabrication process and report the first experimental assessment of their performance at microwaves frequencies (up to 10 GHz), demonstrating experimental GQCs in the pF range with a tuning ratio of 1.34:1 within 1.25 V, and Q-factors up to 12 at 1 GHz. The figures of merit of graphene variable capacitors are studied in detail from 150 to 350 K. Furthermore, we describe a systematic, graphene specific approach to optimize their performance and predict the figures of merit achieved if such a methodology is applied.

Condition for the negative capacitance effect in metal-ferroelectric-insulator-semiconductor devices.

In this paper, we report a detailed study of the negative capacitance field effect transistor (NCFET). We present the condition for the stabilization of the negative capacitance to achieve the voltage amplification across the active layer. The theory is based on Landau's theory of ferroelectrics combined with the surface potential model in all regimes of operation. We demonstrate the validity of the presented theory on experimental NCFETs using a gate stack made of P(VDF-TrFE) and SiO2. The proposed analytical modeling shows good agreement with experimental data.

Millimeter-wave to near-terahertz sensors based on reversible insulator-to-metal transition in VO2.

In the quest for low power bio-inspired spiking sensors, functional oxides like vanadium dioxide are expected to enable future energy efficient sensing. Here, we report uncooled millimeter-wave spiking detectors based on the sensitivity of insulator-to-metal transition threshold voltage to the incident wave. The detection concept is demonstrated through actuation of biased VO2 switches encapsulated in a pair of coupled antennas by interrupting coplanar waveguides for broadband measurements, on silicon substrates. Ultimately, we propose an electromagnetic-wave-sensitive voltage-controlled spike generator based on VO2 switches in an astable spiking circuit. The fabricated sensors show responsivities of around 66.3 MHz.W-1 at 1 µW, with a low noise equivalent power of 5 nW.Hz-0.5 at room temperature, for a footprint of 2.5 × 10-5 mm2. The responsivity in static characterizations is 76 kV.W-1. Based on experimental statistical data measured on robust fabricated devices, we discuss stochastic behavior and noise limits of VO2 -based spiking sensors applicable for wave power sensing in mm-wave and sub-terahertz range.

A single active nanoelectromechanical tuning fork front-end radio-frequency receiver.

Nanoelectromechanical systems (NEMS) offer the potential to revolutionize fundamental methods employed for signal processing in today's telecommunication systems, owing to their spectral purity and the prospect of integration with existing technology. In this work we present a novel, front-end receiver topology based on a single device silicon nanoelectromechanical mixer-filter. The operation is demonstrated by using the signal amplification in a field effect transistor (FET) merged into a tuning fork resonator. The combination of both a transistor and a mechanical element into a hybrid unit enables on-chip functionality and performance previously unachievable in silicon. Signal mixing, filtering and demodulation are experimentally demonstrated at very high frequencies ( > 100 MHz), maintaining a high quality factor of Q = 800 and stable operation at near ambient pressure (0.1 atm) and room temperature (T = 300 K). The results show that, ultimately miniaturized, silicon NEMS can be utilized to realize multi-band, single-chip receiver systems based on NEMS mixer-filter arrays with reduced system complexity and power consumption.

Giant switchable non thermally-activated conduction in 180° domain walls in tetragonal Pb(Zr,Ti)O3.

Conductive domain walls in ferroelectrics offer a promising concept of nanoelectronic circuits with 2D domain-wall channels playing roles of memristors or synoptic interconnections. However, domain wall conduction remains challenging to control and pA-range currents typically measured on individual walls are too low for single-channel devices. Charged domain walls show higher conductivity, but are generally unstable and difficult to create. Here, we show highly conductive and stable channels on ubiquitous 180° domain walls in the archetypical ferroelectric, tetragonal Pb(Zr,Ti)O3. These electrically erasable/rewritable channels show currents of tens of nanoamperes (200 to 400 nA/µm) at voltages ≤2 V and metallic-like non thermally-activated transport properties down to 4 K, as confirmed by nanoscopic mapping. The domain structure analysis and phase-field simulations reveal complex switching dynamics, in which the extraordinary conductivity in strained Pb(Zr,Ti)O3 films is explained by an interplay between ferroelastic a- and c-domains. This work demonstrates the potential of accessible and stable arrangements of nominally uncharged and electrically switchable domain walls for nanoelectronics.

Carbon nanotube crossed junction by two step dielectrophoresis.

The crossed junction formed between a multi walled carbon nanotube (MWCNT) and a bundle of single walled carbon nanotube (SWCNT) is investigated. The junction is fabricated by orthogonally assembling the MWCNT and SWCNT by a two-step dielectrophoresis process. The conventional dielectrophoresis method to self-assemble carbon nanotubes has been modified to be able to align single MWCNT and SWCNT at predefined location on a substrate. At room temperature, the junction has an ohmic behavior with junction resistance of about 500 KOmega or a conductance of 0.05 (e2/h). At 77 K, the onset of a Schottky-like behavior was observed. The resulting junction has an extremely tiny area of less than 20 nm2 and yet supports a current density of 10(7) A/cm2 at 1 V. The proposed fabrication technique is a convenient way to fabricate novel prototype devices to investigate material properties and new device architecture. Following further optimization, this cross-junction can be an interesting candidate for cross-bar like interconnects, with potential applications in dense logic and memory circuits.

Extended gate field-effect-transistor for sensing cortisol stress hormone.

Cortisol is a hormone released in response to stress and is a major glucocorticoid produced by adrenal glands. Here, we report a wearable sensory electronic chip using label-free detection, based on a platinum/graphene aptamer extended gate field effect transistor (EG-FET) for the recognition of cortisol in biological buffers within the Debye screening length. The device shows promising experimental features for real-time monitoring of the circadian rhythm of cortisol in human sweat. We report a hysteresis-free EG-FET with a voltage sensitivity of the order of 14 mV/decade and current sensitivity up to 80% over the four decades of cortisol concentration. The detection limit is 0.2 nM over a wide range, between 1 nM and 10 µM, of cortisol concentrations in physiological fluid, with negligible drift over time and high selectivity. The dynamic range fully covers those in human sweat. We propose a comprehensive analysis and a unified, predictive analytical mapping of current sensitivity in all regimes of operation.

Coupled VO2 Oscillators Circuit as Analog First Layer Filter in Convolutional Neural Networks.

In this work we present an in-memory computing platform based on coupled VO2 oscillators fabricated in a crossbar configuration on silicon. Compared to existing platforms, the crossbar configuration promises significant improvements in terms of area density and oscillation frequency. Further, the crossbar devices exhibit low variability and extended reliability, hence, enabling experiments on 4-coupled oscillator. We demonstrate the neuromorphic computing capabilities using the phase relation of the oscillators. As an application, we propose to replace digital filtering operation in a convolutional neural network with oscillating circuits. The concept is tested with a VGG13 architecture on the MNIST dataset, achieving performances of 95% in the recognition task.

Directed submucosal tunneling permits in-line endoscope positioning for transgastric natural orifice translumenal endoscopic surgery (NOTES).

BACKGROUND: Submucosal dissection is demonstrated to be a technically feasible, safe means of obtaining peroral transgastric peritoneal access for natural orifice translumenal endoscopic surgery (NOTES). The authors hypothesized that their previously described self-approximating translumenal access technique (STAT) could be used to create directed gastric submucosal tunnels permitting in-line endoscope positioning with predetermined abdominal locations that might otherwise be difficult to access. METHODS: In this study, 14 domestic farm swine underwent peroral transgastric peritoneoscopy. Under direct endoscopic visualization, a submucosal tunnel was created by dissecting between the mucosal and muscular layers of the stomach. Each tunnel was created with one of four intraabdominal locations (right upper quadrant, left upper quadrant, lesser sac, and pelvis) as the final target for in-line endoscope positioning. Once peritoneal access had been achieved, in-line positioning was assessed and peritoneoscopy was performed. The submucosal tunnels were closed with endoscopically placed clips. The animals were killed 2 weeks after the procedure, and necropsy was performed. RESULTS: Submucosal tunnels were successfully directed at predetermined intraabdominal targets in 12 of the 14 animals. The mean dissection time required to create the tunnel was 51 +/- 32 min. All the transgastric tunnels were successfully closed with endoscopically placed clips (mean, 3.2 +/- 1.1), and at necropsy showed no evidence of gastrotomy leak in any of the animals. One animal experienced a duodenal perforation unrelated to the transgastric tunneling and was killed on postoperative day 2. The remaining animals recovered and gained weight (mean, 5.5 +/- 1.2 kg) in the 2-week survival period. CONCLUSIONS: Directed submucosal dissection is technically feasible in a porcine model and permits in-line endoscope positioning with predetermined abdominal target locations. The STAT approach provides safe peritoneal access, allows for a simple reliable endoclip closure, and has an excellent short-term survival rate. This method of achieving transgastric access may be an enabling technique for future NOTES procedures.

Negative Capacitance as Universal Digital and Analog Performance Booster for Complementary MOS Transistors.

Boltzmann electron energy distribution poses a fundamental limit to lowering the energy dissipation of conventional MOS devices, a minimum increase of the gate voltage, i.e. 60 mV, is required for a 10-fold increase in drain-to-source current at 300 K. Negative Capacitance (NC) in ferroelectric materials is proposed in order to address this physical limitation of CMOS technology. A polarization destabilization in ferroelectrics causes an effective negative permittivity, resulting in a differential voltage amplification and a reduced subthreshold swing when integrated into the gate stack of a transistor. The novelty and universality of this approach relate to the fact that the gate stack is not anymore a passive part of the transistor and contributes to signal amplification. In this paper, we experimentally validate NC as a universal performance booster: (i) for complementary MOSFETs, of both n- and p-type in an advanced CMOS technology node, and, (ii) for both digital and analog significant enhancements of key figures of merit for information processing (subthreshold swing, overdrive, and current efficiency factor). Accordingly, a sub-thermal swing down to 10 mV/decade together with an enhanced current efficiency factor up to 105 V-1 is obtained in both n- and p-type MOSFETs at room temperature by exploiting a PZT capacitor as the NC booster. As a result of the subthreshold swing reduction and overdrive improvement observed by NC, the required supply voltage to provide the same on-current is reduced by approximately 50%.

3D Smith charts scattering parameters frequency-dependent orientation analysis and complex-scalar multi-parameter characterization applied to Peano reconfigurable vanadium dioxide inductors.

Recently, the field of Metal-Insulator-Transition (MIT) materials has emerged as an unconventional solution for novel energy efficient electronic functions, such as steep slope subthermionic switches, neuromorphic hardware, reconfigurable radiofrequency functions, new types of sensors, terahertz and optoelectronic devices. Employing radiofrequency (RF) electronic circuits with a MIT material like vanadium Dioxide, VO2, requires appropriate characterization tools and fabrication processes. In this work, we develop and use 3D Smith charts for devices and circuits having complex frequency dependences, like the ones resulting using MIT materials. The novel foundation of a 3D Smith chart involves here the geometrical fundamental notions of oriented curvature and variable homothety in order to clarify first theoretical inconsistencies in Foster and Non Foster circuits, where the driving point impedances exhibit mixed clockwise and counter-clockwise frequency dependent (oriented) paths on the Smith chart as frequency increases. We show here the unique visualization capability of a 3D Smith chart, which allows to quantify orientation over variable frequency. The new 3D Smith chart is applied as a joint complex-scalar 3D multi-parameter modelling and characterization environment for reconfigurable RF design exploiting Metal-Insulator-Transition (MIT) materials. We report fabricated inductors with record quality factors using VO2 phase transition to program multiple tuning states, operating in the range 4 GHz to 10 GHz.

An unusual suspect: coconut bezoar after laparoscopic Roux-en-Y gastric bypass.

Nausea and vomiting after gastric bypass are common, but some of the underlying causes may be life threatening or, in some cases, unusual. This case report describes a patient who underwent laparoscopic Roux-en-Y gastric bypass and whose postoperative course was complicated by a bezoar in the gastric pouch. To our knowledge, this is the first published report addressing a coconut bezoar in the gastric pouch after gastric bypass surgery. Coconut (cocos nucifera) is known to form emulsions and suspensions, properties likely to have contributed to this patient's condition. Nutritional counseling should be an ongoing process in the postoperative care of gastric bypass patients in an effort to prevent serious complications that may arise from dietary indiscretions.

Technique for transesophageal endoscopic cardiomyotomy (Heller myotomy): video presentation at the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) 2008, Philadelphia, PA.

BACKGROUND: Previous investigators have shown the feasibility of performing an esophageal myotomy using natural orifice translumenal endoscopic surgery (NOTES), but have been unsuccessful at extending the myotomy onto the body of the stomach. METHODS: In a nonsurvival porcine model, the authors used the self-approximating translumenal access technique (STAT) to create a submucosal tunnel in the upper esophagus and to extend it onto the body of the stomach allowing a complete cardiomyotomy. RESULTS: The STAT approach was successfully used to create a submucosal tunnel and perform a complete myotomy of the gastroesophageal junction without complication. CONCLUSIONS: A complete Heller-type cardiomyotomy can be successfully performed using transesophegeal NOTES.

Three-Dimensional Integrated Ultra-Low-Volume Passive Microfluidics with Ion-Sensitive Field-Effect Transistors for Multiparameter Wearable Sweat Analyzers.

Wearable systems could offer noninvasive and real-time solutions for monitoring of biomarkers in human sweat as an alternative to blood testing. Recent studies have demonstrated that the concentration of certain biomarkers in sweat can be directly correlated to their concentrations in blood, making sweat a trusted biofluid candidate for noninvasive diagnostics. We introduce a fully on-chip integrated wearable sweat sensing system to track biochemical information at the surface of the skin in real time. This system heterogeneously integrates, on a single silicon chip, state-of-the-art ultrathin body (UTB) fully depleted silicon-on-insulator (FD-SOI) ISFET sensors with a biocompatible microfluidic interface, to deliver a "lab-on-skin" sensing platform. A full process for the fabrication of this system is proposed in this work and is demonstrated by standard semiconductor fabrication procedures. The system is capable of collecting small volumes of sweat from the skin of a human and posteriorly passively driving the biofluid, by capillary action, to a set of functionalized ISFETs for analysis of pH level and Na+ and K+ concentrations. Drop-casted ion-sensing membranes on different sets of sensors on the same substrate enable multiparameter analysis on the same chip, with small and controlled cross-sensitivities, whereas a miniaturized quasireference electrodes set a stable analyte potential, avoiding the use of a cumbersome external reference electrode. The progress of lab-on-skin technology reported here can lead to autonomous wearable systems enabling real-time continuous monitoring of sweat composition, with applications ranging from medicine to lifestyle behavioral engineering and sports.

Genuinely Ferroelectric Sub-1-Volt-Switchable Nanodomains in Hf xZr(1- x)O2 Ultrathin Capacitors.

The new class of fully silicon-compatible hafnia-based ferroelectrics with high switchable polarization and good endurance and thickness scalability shows a strong promise for new generations of logic and memory devices. Among other factors, their competitiveness depends on the power efficiency that requires reliable low-voltage operation. Here, we show genuine ferroelectric switching in Hf xZr(1- x)O2 (HZO) layers in the application-relevant capacitor geometry, for driving signals as low as 800 mV and coercive voltage below 500 mV. Enhanced piezoresponse force microscopy with sub-picometer sensitivity allowed for probing individual polarization domains under the top electrode and performing a detailed analysis of hysteretic switching. The authentic local piezoelectric loops and domain wall movement under bias attest to the true ferroelectric nature of the detected nanodomains. The systematic analysis of local piezoresponse loop arrays reveals a totally unexpected thickness dependence of the coercive fields in HZO capacitors. The thickness decrease from 10 to 7 nm is associated with a remarkably strong decrease of the coercive field, with about 50% of the capacitor area switched at coercive voltages ≤0.5 V. Our explanation consistent with the experimental data involves a change of mechanism of nuclei-assisted switching when the thickness decreases below 10 nm. The practical implication of this effect is a robust ferroelectric switching under the millivolt-range driving signal, which is not expected for the standard coercive voltage scaling law. These results demonstrate a strong potential for further aggressive thickness reduction of HZO layers for low-power electronics.