Aligned carbon nanotube based ultrasonic microtransducers for durability monitoring in civil engineering

International audienceStructural health monitoring of porous materials such as concrete is becoming a major component in our resource-limited economy, as it conditions durable exploitation of existing facilities. Durability in porous materials depends on nanoscale features which need to be monitored in situ with nanometric resolution. To address this problem, we put forward an approach based on the development of a new nanosensor, namely a capacitive micrometric ultrasonic transducer whose vibrating membrane is made of aligned single-walled carbon nanotubes (SWNT). Such sensors are meant to be embedded in large numbers within a porous material in order to provide information on its durability by monitoring in situ neighboring individual micropores. In the present paper, we report on the feasibility of the key building block of the proposed sensor: we have fabricated well-aligned, ultra-thin, dense SWNT membranes that show above-nanometer amplitudes of vibration over a large range of frequencies spanning from 100 kHz to 5 MHz

Micro−transducteur ultrasonique capacitif à membrane de nanotubes de carbone : Perspectives pour le suivi immergé de la durabilité des matériaux cimentaires

Nous présentons des éléments de la conception, la réalisation et la caractérisation d'un micro−transducteur ultrasonique capacitif haute-fréquence dont la membrane vibrante est faite de nanotubes de carbone alignés. Le dispositif est conçu spécifiquement pour l'instrumentation immergée de la microporosité des matériaux cimentaires. La modélisation élasto−acoustique du dispositif valide préliminairement son intérêt applicatif pour la métrologie de la microporosité

Recent Advances in Molecular Electronics Based on Carbon Nanotubes

Carbon nanotubes (CNTs) have exceptional physical properties that make them one of the most promising building blocks for future nanotechnologies. They may in particular play an important role in the development of innovative electronic devices in the fields of flexible electronics, ultra-high sensitivity sensors, high frequency electronics, opto-electronics, energy sources and nano-electromechanical systems (NEMS). Proofs of concept of several high performance devices already exist, usually at the single device level, but there remain many serious scientific issues to be solved before the viability of such routes can be evaluated. In particular, the main concern regards the controlled synthesis and positioning of nanotubes. In our opinion, truly innovative use of these nano-objects will come from: i) the combination of some of their complementary physical properties, such as combining their electrical and mechanical properties, ii) the combination of their properties with additional benefits coming from other molecules grafted on the nanotubes, and iii) the use of chemically- or bio-directed self-assembly processes to allow the efficient combination of several devices into functional arrays or circuits. In this article, we outline the main issues concerning the development of carbon nanotubes based electronics applications and review our recent results in the field

High-sensitivity versus conventional troponin in the emergency department for the diagnosis of acute myocardial infarction

International audienceINTRODUCTION: Recently, newer assays for cardiac troponin (cTn) have been developed which are able to detect changes in concentration of the biomarker at or below the 99th percentile for a normal population. The objective of this study was to compare the diagnostic performance of a new high-sensitivity troponin T (HsTnT) assay to that of conventional cTnI for the diagnosis of acute myocardial infarction (AMI) according to pretest probability (PTP). METHODS: In consecutive patients who presented to our emergency departments with chest pain suggestive of AMI, levels of HsTnT were measured at presentation, blinded to the emergency physicians, who were asked to estimate the empirical PTP of AMI. The discharge diagnosis was adjudicated by two independent experts on the basis of all available data. RESULTS: A total of 317 patients were included, comprising 149 (47%) who were considered to have low PTP, 109 (34%) who were considered to have moderate PTP and 59 (19%) who were considered to have high PTP. AMI was confirmed in 45 patients (14%), 22 (9%) of whom were considered to have low to moderate PTP and 23 (39%) of whom were considered to have high PTP (P < 0.001). In the low to moderate PTP group, HsTnT levels ≥ 0.014 μg/L identified AMI with a higher sensitivity than cTnI (91%, 95% confidence interval (95% CI) 79 to 100, vs. 77% (95% CI 60 to 95); P = 0.001), but the negative predictive value was not different (99% (95% CI 98 to 100) vs. 98% (95% CI 96 to 100)). There was no difference in area under the receiver operating characteristic (ROC) curve between HsTnT and cTnI (0.93 (95% CI 0.90 to 0.98) vs. 0.94 (95% CI 0.88 to 0.97), respectively). CONCLUSIONS: In patients with low to moderate PTP of AMI, HsTnT is slightly more useful than cTnI. Our results confirm that the use of HsTnT has a higher sensitivity than conventional cTnI

Carbon nanotubes based ultrasonic transducer: realization process, morphological and mechanical properties

For instrumentation of microporosity in cementitous materials, carbon nanotubes based capacitive ultrasonic transducers (cMUT) are promising sensors. Their interest lies in the combination of high working frequencies (1 GHz) with small dimensions (1 µm²). In the proposed device, the cMUT membrane is made of aligned single-walled carbon nanotubes (SWNT) bridging a gap over a command electrode. We will describe the realization process of the vibrating membrane and its characterizations. First step of the device realization is the dispersion of SWNTs in N-methylpyrrolidone. Then, nanotubes are aligned by dielectrophoresis (DEP) between metallic electrodes onto a SiO2 substrate. A metallic layer is deposited over the electrodes edges to prevent nanotubes from slipping when suspended. The underlying SiO2 is then etched to release the membrane. Relevant features of the membrane are nanotubes alignment and density. Via SEM imaging, we have linked them with DEP operating parameters, in agreement with theoretical properties of DEP. To put a figure on membrane features, we are working on SEM image processing for nanotubes recognition. The method is based on advanced noise removal and contrast enhancement. First results of identification and measurement of intermeshed nanotubes on SEM pictures will be presented. We also mapped the Young's modulus of a suspended membrane using an AFM in contact mode, over surfaces of about 1 µm² surface. It opens the way for calculation of localized Young modulus, Poisson's ratio and thickness measurement of the membrane. We will check for correlations between mechanical data and quantitative properties of the deposition obtained from image processing. The optimization of membrane realization process and characterization techniques are presented, describing the present progress of our cMUT project. Next step will be actuation of the membrane to demonstrate vibrations at low frequency

Mechanistic Insights and Technical Challenges in Sulfur-Based Batteries:A Comprehensive <i>In Situ/Operando</i> Monitoring Toolbox

Batteries based on sulfur cathodes offer a promising energy storage solution due to their potential for high performance, cost-effectiveness, and sustainability. However, commercial viability is challenged by issues such as polysulfide migration, volume changes, uneven phase nucleation, limited ion transport, and sluggish sulfur redox kinetics. Addressing these challenges requires insights into the structural, morphological, and chemical evolution of phases, the associated volume changes and internal stresses, and ion and polysulfide diffusion within the battery. Such insights can only be obtained through real-time reaction monitoring within the battery's operational environment, supported by molecular dynamics simulations and advanced artificial intelligence-driven data analysis. This review provides an overview of in situ/operando techniques for real-time tracking of these processes in sulfur-based batteries and explores the integration of simulations with experimental data to provide a holistic understanding of the critical challenges, enabling advancements in their development and commercial adoption

High energy density lithium-battery anode materials based on graphite-silicon nanowire composites

International audienceSilicon is a promising anode material for increasing energy density in lithium-ion batteries. In composite with graphite, the present dominant anode material, it allows to increase progressively the capacity of the anode by up to a factor of 10, and the overall energy density of the battery by up to 30%. However silicon has to be incorporated as a nanomaterial in the electrode to avoid fast decay due to pulverization while cycling. I will briefly review the forms of nano-silicon for lithium battery anodes, the challenges in synthesis and formulation, and the effect on performance in cycling. We recently grew a series of silicon nanoparticles and nanowires of different sizes, and cycled them in the same conditions [1]. I will present the result of this comparison, showing unexpected effects of size and shape of silicon on its electrochemical behavior in lithium batteries. Our team proposes a simple process of direct growth of silicon nanowires (SiNW) on graphite, containing up to 40wt.% Si. The interest of this compact, robust process will be discussed. This micropowder can directly enter in the slurry for the preparation of lithium battery anodes [2] following standard procedures. This material can be optimized for a specific capacity of 1000mAh/g, and holds more than 500 cycles at 2C (30 minute charge, 30 minute discharge). A large irreversible capacity loss is observed in the first cycle, as for many nanomaterials, but then the specific capacity retention is unusually high for silicon-rich anodes, and they can be incorporated in lithium-ion batteries vs NMC cathodes. I will finally address material-design issues to increase the performance of the material. In particular, I will discuss replacing gold by tin as the metallic catalysts required for SiNW growth, and possible means to reduce the irreversible capacity loss in the first cycle. [1] C. Keller et al., Nanomaterials 2021, 11, 307, 10.3390/nano11020307[2] S. Karuppiah et al., ACS Nano 2020, 14, 12006, 10.1021/acsnano.0c0519

Nanotubes de carbone comme matériau semi-conducteur pour l'électronique plastique : trier ou ne pas trier ?

National audienceLes nanotubes de carbone mono-parois sont obtenus par croissance d'un mélange de nanotubes semi-conducteurs et de nanotubes métalliques de diamètres similaires, mais différents par la chiralité de l'enroulement du feuillet de graphène qui constitue le tube. La synthèse séparée des deux types a été envisagée mais s'avère très difficile et à faible rendement. Cependant, les nanotubes semi-conducteurs sont d'excellents candidats pour l'électronique plastique : manipulable en solution comme des composés organiques, ils présentent d'excellentes mobilités et rapports courant ouvert/courant fermé proches de ceux des semi-conducteurs inorganiques.Pour éviter les court-circuit dus aux nanotubes métalliques présents dans le mélange de croissance, plusieurs méthodes de séparation ont été développées dans les 15 dernières années, dont deux ont permis la mise sur le marché de matériaux séparés. Nous verrons un aperçu de ces méthodes de séparation et de leurs usages pour l'électronique plastique, en comparaison d'autres matériaux imprimables. Notre laboratoire développe par ailleurs un traitement chimique sélectif permettant de supprimer la conductivité des nanotubes métalliques tout en conservant la qualité des nanotubes semi-conducteurs. Ce traitement simple, en phase aqueuse, évite la nécessité de séparer les deux types et fournit un matériau semi-conducteur imprimable à coût réduit