Carbon nanotube are exceptional mechanical resonators. Indeed, they are extremely light, with masses in the range of ~ag (1 ag = 10-18g). In addition, as bottom-up materials, they do not suffer from surface defect as their top-down counterparts (MEMS etched from silicon or nitride substrates). From these 2 features stems their exquisite mass sensitivity as demonstrated by Chaste et al[1] with a sensitivity of 1.4 yg in a cryogenic environment. Yet, this sensitivity was reported to be much worse at room temperature, about 25 zg[2]. This has hindered the use of CNTs as sensors in real-life applications. In this work, we propose a unique set-up to track in real time the vibrations of a individual single-walled CNT (SWCNTs) at room temperature. It allows us to demonstrate a record mass sensitivity of 0.2 yg +/- 0.17 yg (1 yg = 10-24 g, the mass of a single proton).We carefully investigated the noise mechanisms that could be limiting the sensitivity: set-up noise, interaction with the gas phase and Brownian motion to name only the most important ones. We found that our device operates closely to the Brownian noise limit and is not limited by external sources of noise. Surprisingly, increasing the pressure up to 35 mbar (after which we could not detect the motion due to viscous damping) does not seem to degrade the sensitivity, which might be preserved up to ambient pressure. Finally, yet importantly, the exquisite sensitivity observed here is similar for several devices, making it a reliable and reproducible feature. This opens up the possibility to perform single-molecule sensing, in various contexts such as biological applications, mass spectrometry or surface science[1,3].[1] J. Chaste, A. Eichler, J. Moser, G. Ceballos, R. Rurali, A. Bachtold (2012). A nanomechanical mass sensor with yoctogram resolution, Nat. Nano, 7, 5, 301-304.[2] B. Lassagne, D. Garcia-Sanchez, A. Aguasca, A. Bachtold (2008). Ultrasensitive mass sensing with a nanotube electromechanical resonator, Nano. Let., 8, 11, 3735 – 3738.[3] P. Robin, L. Bocquet (2023). Nanofluidics at the crossroads, Soft Cond. Matt., preprint.

This article shows the differentiation between water adsorbed outside of a single-walled carbon nanotube (CNT) and that confined inside. This distinction is made possible by tracking the electronic transport of a CNT-based field effect transistor constructed with an individual nanotube and exposed to controlled environments. The presence of water shifts the electrical neutrality point, indicating charge transfer between the nanotube and its environment. We identify three types of water molecules: (i) chemically adsorbed on the SiO2 surface, forming silanol groups, (ii) physically adsorbed outside the nanotube, and (iii) confined inside. The first type is eliminated only by high-temperature treatment under vacuum, while the latter two desorb at room temperature under moderate or high vacuum, i.e. 10−3 mbar. We observe that water confinement inside the nanotube is fast and thermodynamically favorable, with no qualitative influence from the metallicity of the nanotube.

Despite several decades of development, microfluidics lacks a sealing material that can be readily fabricated, leak-tight under high liquid water pressure, stable over a long time, and vacuum compatible. In this paper, we report the performances of a micro-scale processable sealing material for nanofluidic/microfluidics chip fabrication, which enables us to achieve all these requirements. We observed that micrometric walls made of SU-8 photoresist, whose thickness range from 35 μm to 135 μm, are at least leak-tight to 1.5 bars and up to 5.5 bars, exhibit no water porosity even after 2 months of aging, and are able to sustain under 10−5 mbar vacuum. This sealing material is therefore reliable and versatile for building microchips, part of which must be isolated from liquid water under pressure or vacuum. Moreover, the fabrication process we propose does not require the use of either aggressive chemicals or high-temperature or high-energy plasma treatment. It thus opens a new perspective to seal microchips with sensitive surfaces containing nanomaterials.

Single walled carbon nanotubes (SWCNTs) have gained interest in the field of nanoscaleconfinement of the fluids, with a variety of unexpected phenomena such as spontaneous filing,frictionless mas transport, unusual phase diagram, etc. (1). The majority of these phenomenaremains unexplored and requires experimental confirmation. In addition, the field requiresa sensitive method to carry out measurement in the level of individual and SWCNT, as theconfinement is sensitive to the tube diameter. On the other hand, the intrinsic and extrinsicelectronic properties of the SWCNT is shown to be sensitive to the diameter, defects, doping,adsorbates, and environment via SWCNT field effect transistors (SWCNT-FET) (2,3).In this contribution, we show that the electronic response of the individual SWCNT based fieldeffect transistor is an essential tool to study water-CNT coupling mechanism and accuratelyidentify the impact of water confined inside the nanotube. We investigate the charge transfercharacteristics of the SWCNT-FET, while exposing several individual SWCNT first unopened,then opened to different environment, such as ambient air, air humidity, vacuum and currentannealing under vacuum. We demonstrate that it is possible to assign CNT doping as the mainmechanism behind water-CNT coupling, and distinguish between water adsorbed outside ofthe nanotube from confined inside. Precisely, we found that putting the device under secondaryvacuum, after exposing to air humidity, shift the gate voltage neutrality point of opened SWCNTtowards more negative values, however, the secondary vacuum has no effect on the same SWCNTwhen it was closed. We also demonstrate that this behavior is independent CNT metallicity,assuming that the nanotube’s surface has been pre-cleaned using current annealing. We willalso discuss the water adsorption and desorption kinetics and dynamics.Our findings open up the possibility of using CNTFET to address long-standing issues in thenanofluidic community regarding the behavior of water confinement at the nanoscale, and alsoto use them for reliable, sensitive, and selective chemical and biological sensors.

Despite several decades of development, microfluidics lacks a sealing material that can be readily fabricated, leak-tight under high liquid water pressure, stable over a long time, and vacuum compatible. In this paper, we report the performances of a micro-scale processable sealing material for nanofluidic/microfluidics chip fabrication, which enables us to achieve all these requirements. We observed that micrometric walls made of SU-8 photoresist, whose thickness can be as low as 35 $μ$m, exhibit water pressure leak-tightness from 1.5 bar up to 5.5 bar, no water porosity even after 2 months of aging, and are able to sustain under $10^{-5}$ mbar vacuum. This sealing material is therefore reliable and versatile for building microchips, part of which must be isolated from liquid water under pressure or vacuum. Moreover, the fabrication process we propose does not require the use of aggressive chemicals or high-temperature or high-energy plasma treatment. It thus opens a new perspective to seal microchips where delicate surfaces such as nanomaterials are present.