Response of nanogravimetric detector is based on adsorption of molecules on the surface of a vibrating beam. For any compound, NGD temperature (originally from 40 to 200°C) is the main operating parameter to control its sensitivity. Introduction of a cooling unit to enlarge the operating temperature range (down to -100°C) led to a substantial improvement in detection sensitivity and a significant reduction in quantification limits. The response of tetrahydrothiophene (THT) over a wide temperature range was deeply investigated: peak height increased exponentially as temperature decreased, while noise was slightly lowered. Consequently, the limit of quantification (LOQ) of THT can be reduced from 22 ppm at 50°C to 0.16 ppm at -65°C. However, significant peak tailing was observed at very low temperatures, which may compromise the separation of complex mixtures. THT chromatographic peaks were successfully modeled using an Exponentially Modified Gaussian (EMG) function, and the temperature dependence of the EMG adjusted parameters has been discussed.

Environmental monitoring and air quality survey during long-term field campaign tests, especially in lowaccessibility or extreme environments, requires robust, standalone and autonomous analyzer with low gas consumption and minimal human intervention. The current states of art emphasize the need to develop miniaturized GC based on novel detectors that offers the best compromise between carrier gas consumption, detection limits and panel of measured VOCs. This work presents the development and optimization of MAVERIC, a miniaturized and autonomous Gas Chromatograph system coupled to an innovative Nano Gravimetric Detector (NGD) based on NEMS (nano-electromechanical-system) resonator. A homemade software is developed to control the instrument as well as the electronics modules. The system operates at low flow rate (2 mL.min-1) of helium used as carrier gas, and allows the measurements of VOCs from C6 to C10 in less than 30 min. A mixture of isoprene, benzene, toluene and alpha-pinene is used to optimize experimental conditions. Under optimal conditions, the detection limit, the stability, the repeatability and the linearity of the analytical system are assessed. A detection limit of sub-ppb to few ppt level was determined for C6 and C9 compounds, respectively. The lowest detection limit corresponds to the highest molecular weight compounds due to NGD sensitivity at ambient temperature. The system is standalone, portable, robust and equipped with 4G connection that allows remote control of the instrument and easy data export. It is very adapted for a long period field campaign test, environmental monitoring and air quality survey outdoors and in low-accessibility or extreme environments.

Hydrodynamics, efficiency, and loading capacity of two semi-packed columns with different cross sections (NANO 315 µm x 18 µm; CAP 1000 µm x 28 µm) and similar pillar diameter and pillar-pillar distance (respectively 5 µm and 2.5 µm) have been compared in high-pressure gas chromatography. A flow prediction tool has been first designed to determine pressure variations and hold-up time across the chromatographic system taking into account the rectangular geometry of the ducts into the semi-packed columns. Intrinsic values of Height Equivalent to Theoretical Plate were determined for NANO and CAP columns using helium as carrier gas and similar values have been obtained (30 µm) for the two columns. Loading capacity of semi-packed columns were determined for decane at 70 °C using helium, and the highest value was obtained from CAP column (larger cross section and stationary phase content). Finally, significant HETP improvement (down to 15 µm) and peak shape were observed when carbon dioxide was used as carrier gas, suggesting mobile phase adsorption on stationary phase in high pressure conditions.

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The integration of semi-packed columns in gas chromatography has garnered significant interest in recent years. This review investigates various aspects of semi-packed columns, encompassing their fundamental concept, fabrication process, coating techniques, and exploration of various designs employed in gas chromatography. Diverse applications of semi-packed columns in gas chromatography are presented to showcase their practical significance and potential. By examining the current state of research and advancements in semi-packed column technology, this review aims to provide valuable insights for researchers seeking to enhance the capabilities of gas chromatography systems using innovative column designs.

Nano-gravimetric detector (NGD) has been recently introduced as miniaturized gas chromatography detector. The NGD response is based on an adsorption-desorption mechanism of compounds between the gaseous phase and the NGD porous oxide layer. The NGD response was characterized by hyphenating NGD in-line with FID detector and a chromatographic column. Such method led to the full adsorption-desorption isotherms of several compounds in a single run. Langmuir model was used to describe the experimental isotherms, and the initial slope of the isotherm (Mm.KT) obtained at low gas concentration was used to compare the NGD response for different compounds (good repeatability was demonstrated with a relative standard deviation lower than 3%). The column-NGD-FID hyphenated method was validated using alkane compounds according to the number of carbon atoms in the alkyl chain and to the NGD temperature (all results agreed with thermodynamic relations associated to partition coefficient). Furthermore, relative response factor to alkanes, for ketones, alkylbenzenes, and fatty acid methyl esters have been obtained. These relative response index values led to easier calibration of NGD. The established methodology can be used for any sensor characterization based on adsorption mechanism.

A nano-gravimetric detector (NGD) for gas chromatography is based on a nanoelectromechanical array of adsorbent-coated resonating double clamped beams. NGD is a concentration-sensitive detector and its sensitivity is analyte-dependent based on the affinity of the analyte with the porous layer coated on the NEMS surface. This affinity is also strongly related to the NGD temperature (NGD working temperature can be dynamically set up from 40 to 220 °C), so the sensitivity can be tuned through temperature detector control. An adsorption-desorption model was set up to characterize the NGD response on a large set of n-alkanes from C10 to C22 at different NGD temperatures. For fast identification of petroleum mixture based on chromatogram fingerprint, a general strategy for NGD temperature program design was developed leading to a constant relative response factor between 0.96 and 1.03 for all the alkanes, and then chromatograms are very similar to those obtained with a flame ionization detector (FID). The analysis of a real petroleum fluid was also performed and compared to FID results: quantitative results obtained for all the analytes were satisfactory according to precision (<5%) and accuracy (average relative error = 4.3%). Based on such temperature control strategy, NGD sensitivity and the dynamic linear range can be adjusted and detection limits at a picogram level can be easily achieved for all n-alkanes.

This brief presents an active distributed clock generator for manycore systems-on-chip consisting of a $10\times 10$ network of coupled all-digital phase-locked loops, achieving less than 38 ps phase error between neighboring oscillators over a frequency range of 700–840 MHz at $V_{\text {DD}} = 1.1$ V. The network is highly robust against $V_{\text {DD}}$ variations. An energy cost of 2.7 $\mu \text{W}$ /MHz per node is 7 times lower than that in analog implementations of similar architectures and is twice lower than that in conventional H-tree architectures. This is the largest on-chip all-digital phase-locked loop network ever implemented. With clock generation nodes linked only locally, this solution is proven to be scalable. The presented clock generation network does not require any external reference, except for the start-up frequency selection, generating a synchronized signal in fully autonomous mode and maintaining frequency stability within 0.09% during 1700 seconds. Such a network of frequency and phase synchronized oscillators can be used as a source for local clocking areas.

One of the main challenges to overcome to perform nanomechanical mass spectrometry analysis in a practical time frame stems from the size mismatch between the analyte beam and the small nanomechanical detector area. We report here the demonstration of mass spectrometry with arrays of 20 multiplexed nanomechanical resonators; each resonator is designed with a distinct resonance frequency which becomes its individual address. Mass spectra of metallic aggregates in the MDa range are acquired with more than one order of magnitude improvement in analysis time compared to individual resonators. A 20 NEMS array is probed in 150 ms with the same mass limit of detection as a single resonator. Spectra acquired with a conventional time-of-flight mass spectrometer in the same system show excellent agreement. We also demonstrate how mass spectrometry imaging at the single-particle level becomes possible by mapping a 4-cm-particle beam in the MDa range and above.

The evolutions of medicine covering genome to exposome (i.e. all types of environmental exposures) [1] opened new paths of development for electronics including low power sensors. Additionally, the frontiers for new generations of sensors between smart-living, environment and health are fading. In this paper, we will give examples based on our developments in emerging autonomous sensors and medical devices, and show how they can be included in our daily life.

Frequency stability is key to the performance of nanoresonators. This stability is thought to reach a limit with the resonator's ability to resolve thermally induced vibrations. Although measurements and predictions of resonator stability usually disregard fluctuations in the mechanical frequency response, these fluctuations have recently attracted considerable theoretical interest. However, their existence is very difficult to demonstrate experimentally. Here, through a literature review, we show that all studies of frequency stability report values several orders of magnitude larger than the limit imposed by thermomechanical noise. We studied a monocrystalline silicon nanoresonator at room temperature and found a similar discrepancy. We propose a new method to show that this was due to the presence of frequency fluctuations, of unexpected level. The fluctuations were not due to the instrumentation system, or to any other of the known sources investigated. These results challenge our current understanding of frequency fluctuations and call for a change in practices.

The miniaturization and cost reduction of a gas chromatograph is addressed in this paper, leveraging on nano-electromechanical systems (NEMS) detectors and a mixed-signal integrated circuit. The instrument and chip architectures are thoroughly described, characterized, and compared to other approaches like thermal conductivity detectors (TCDs). The 28 nm CMOS circuit addresses the sequential and parallel driving and readout of NEMS arrays with resonance modes in the 10 MHz to 1 GHz range. It integrates an analog-to-digital converter (ADC), two digital-to-analog converters (DACs), and 4 tone DSP [lock-in amplifier (LIA) and direct digital synthesizer (DDS)] for increased throughput. Its area is 0.9 mm(2) and it draws 68 mW of power compared to 10 cm(2) and 3 W in previous discrete implementations. Lab and field characterizations show that the combined NEMS and IC can provide down to 10 ppb limits of detection (LOD) on selected gas species.

Supplementary Figure S1. Complete mapping of datapoints and references of Figure 1 in the main text. 1. Chaste, J. et al. A nanomechanical mass sensor with yoctogram resolution. Nat. Nanotechnol. 7, 301–304 (2012). After annealing 2. Chaste, J. et al. A nanomechanical mass sensor with yoctogram resolution. Nat. Nanotechnol. 7, 301–304 (2012). Before annealing 3. Jensen, K., Kim, K. & Zettl, A. An atomic-resolution nanomechanical mass sensor. Nat. Nanotechnol. 3, 533–537 (2008). 4. Chiu, H.-Y., Hung, P., Postma, H. W. C. & Bockrath, M. Atomic-Scale Mass Sensing Using Carbon Nanotube Resonators. Nano Lett. 8, 4342–4346 (2008). 5. Chen, C. et al. Performance of monolayer graphene nanomechanical resonators with electrical readout. Nat. Nanotechnol. 4, 861–867 (2009). 6. Bartsch, S. T., Rusu, A. & Ionescu, A. M. Phase-locked loop based on nanoelectromechanical resonant-body field effect transistor. Appl. Phys. Lett. 101, 153116 (2012). 7. Sansa, M., Fernández-Regúlez, M., Llobet, J., San Paulo, Á. & Pérez-Murano, F. Highsensitivity linear piezoresistive transduction for nanomechanical beam resonators. Nat. Commun. 5, (2014). Frequency fluctuations in silicon nanoresonators

This paper presents NEMS gas sensors implemented in a breakthrough multigas analysis system. The NEMS mass sensors are collectively fabricated, functionalized and packaged at wafer level. NEMS array resonators exhibit good frequency stability (Allan deviation <5.10(-7) in air). After implementation in the multigas analysis system, the capability to analyze complex gas mixtures for Industrial and Indoor Air Quality monitoring has been demonstrated, with typical Limit of Detection in ppm down to ppb level.

NEMS based sensors open several opportunities for integrated solutions in emerging domains as chemical analysis and life science. With critical dimensions ranging between 10 and 100 nm, those devices can be made at the VLSI scale, possibly co-integrated with CMOS and are well suited for autonomous, highly sensitive or dense sensors. Several applications will be presented, as complex gas portable recognitions systems, mass spectrometry, or bio-sensors.

Progress in silicon technology has promoted NEMS sensors as viable and highly sensitive candidates for gravimetric applications such as gas sensing, mass spectrometry and biochemical analysis [1]. The high sensitivity to mass is related to the small dimensions and intrinsic mass of the NEMS themselves, which results in resonant frequencies in the 10MHz-to-1GHz range and drive voltages reaching 1V to 10V. Such a combination of frequencies and voltages is a challenge for the driving electronics. Although several promising approaches using NEMS/CMOS co-integration have been recently published [2], many experiments in the field are currently using discrete electronic boards and specialized lab instruments. To respond to size, power and cost demands, an IC implementing the most critical parts of the full system is described hereafter.

We report on the first experimental demonstration of a self-oscillator based on a single-crystal silicon NEMS resonator monolithically co-integrated with a CMOS circuitry. The latter, composed only by seven transistors, is manufactured with a very low-cost 0.35μm technology. The NEMS-CMOS self-oscillator pixel is as small as 50×70 μm2 (pads excluded) and can oscillate near 8MHz. In this paper are described the NEMS-CMOS oscillator characteristics and the implementation method of the self-oscillating loop.