Patent Description:
The precise manipulation of liquids at the micro and nanoscales is a key issue in several scientific fields, including cell biology, chemistry, engineering, and printing or patterning. Closed systems (i.e., channels, nozzles, or tubes) are mainly used for handling fluids at the submillimeter scale. However, due to their confined geometry, said fluidic systems pose several technical challenges, such as high flow resistance and propensity to clogging and bubble-driven flow perturbation [<NPL>; <NPL>;<NPL>].

Open fluidic systems are consolidating as an alternate technological approach for the detection and manipulation of very small volumes due to lower hydrodynamic resistance, simplicity of fabrication, ease in cleaning, accessibility for liquid handling and increased gas bubbles elimination. Characterized by having, at least, one area of the device open to air, these systems are capable of transporting liquid droplets directionally by gradient in shape, gradient in surface wettability or DC/AC voltage application, enabling self-driven liquid flow with exceptionally large liquid/channel volume ratios. Among them are flexible fiber arrays [<NPL>], rigid nanowires [<NPL>], spider silks [<NPL>], cactus spines [<NPL>], and conical wires [<NPL>].

Despite some degree of qualitative control of liquid transport in open fluidic systems, precise quantitative control is currently limited by the difficulty to provide precise flow measurements. So far, flow measurements are mostly based on the estimation of volume changes of liquid droplets acting as initial reservoirs or being involved in the transport itself, through diverse imaging techniques [<NPL>; <NPL>; <NPL>; <NPL>; <NPL>]. Besides the limitations concerning accuracy, these estimations are useless for the development of compact integrated devices and instruments that fully exploit the functional potential of open fluidic systems.

Document <CIT> refers to a nanomechanical mass flow meter and controller device.

The present invention proposes a solution to the technical problem mentioned above, by means of a nanomechanical mass flow meter and controller device that allows real-time measurement and control of mass flow in open nanofluidic systems.

A first object of the present invention relates to a nanomechanical mass flow meter and controller device for open nanofluidic systems comprising:.

Advantageously, the device of the invention further comprises:.

Within the scope of interpretation of the present invention, the expression "conducting liquid" will be understood as any liquid solution that contains ions (i.e., atoms or small groups of atoms that have a positive or negative electrical charge). Examples of conducting liquids are any type of salt dissolved in water and ionic liquids (that is, molten salts originated from the association of organic cations and organic/inorganic anions).

In a preferred embodiment of the device of the invention, the mechanical resonator sensor comprises a cantilever resonator attached to a nanowire, or a nanowire resonator. In both cases, the nanowire acts as receiving means. Preferably, the nanowire resonator or the nanowire attached to the cantilever resonator comprises a metal or a semiconductor material and, more preferably, silicon (Si), germanium (Ge), silicon carbide (SiC), indium arsenide (InAs), indium phosphide (InP), gallium arsenide (GaAs), gallium phosphide (GaP), indium antimonide (InSb), gallium antimonide (GaSb), gallium nitride (GaN), indium nitride (InN), aluminum nitride (AIN), or any combination thereof.

In another preferred embodiment of the device of the invention, the reservoir comprises a support made of a conductive material, preferably, gold or platinum-iridium.

In yet another preferred embodiment of the device of the invention, the reservoir is adapted for containing one or more droplets of an ionic liquid. Preferably, said ionic liquid comprises:.

In yet another preferred embodiment of the device of the invention, the selecting means comprises one or more piezoelectric, optomechanical, electrostatic, capacitive, resistive, or photothermal actuators to excite the flexural modes of the mechanical resonator sensor.

In yet another preferred embodiment of the device of the invention, the monitoring means comprises one or more photodetectors, optomechanical, electrostatic, capacitive, or resistive transducers to detect nanoscale deflections of the mechanical resonator sensor.

In yet another preferred embodiment of the device of the invention, said device further comprises laser emission means arranged in such a way that the emitted laser beam is reflected or backscattered by the mechanical resonator sensor and collected by the monitoring means.

In yet another preferred embodiment of the device of the invention, said device further comprises laser focusing means adapted for focusing the laser beam reflected or backscattered by the mechanical resonator sensor on the monitoring means.

In yet another preferred embodiment of the device of the invention, said device further comprises imaging means adapted for taking optical images of the mechanical resonator sensor and the reservoir.

In yet another preferred embodiment of the device of the invention, said device further comprises processing means configured to process an electrical signal from the monitoring means. Preferably, said processing means comprises a digital acquisition (DAQ) board or a lock-in amplifier (LIA).

A second object of the invention relates to a method for controlling mass flow in open nanofluidic systems by means of a device according to any of the embodiments herein described. Advantageously, the method comprises performing the following steps:.

In a preferred embodiment of the method of the invention, said method further comprises a step of determining a mass flow rate of conducting liquid ṁL along the receiving means by dividing the mass of conducting liquid mL by the period of time Δt.

In another preferred embodiment of the method of the invention, the voltage, in absolute value, applied by the dispensing means is below <NUM> V. Preferably, between <NUM> and <NUM> V and, more preferably, between <NUM> and <NUM> V.

In another preferred embodiment of the method of the invention, the conducting liquid loaded in the reservoir comprises an ionic liquid and is subject to a pressure lower than <NUM> atm.

A third object of the invention relates to a synthesis method of semiconductor nanowires as receiving means of a device according to any of the embodiments herein described, based on vapor-liquid-solid mechanism for single-crystal growth. Advantageously, the method comprises performing the following steps in any technically possible order:.

Under the scope of interpretation of the present invention, the expression "growth semiconductor substrate" will be understood as any semiconductor substrate wherein a plurality of nanowires can be formed by following the method of the invention. Furthermore "metal catalyst" will be understood as any metal material that can act as a seed of the growth of a semiconductor nanowire.

Unlike technological approaches known in the prior art, the synthesis method of the invention allows fabricating semiconductor nanowires up to <NUM> in length with controllable tapered morphology and orientation. Tapered cross-sectional semiconductor nanowires have been ascribed to a gradual decrease of the metal-semiconductor alloy droplets diameter during the nanowire growth process due to loss of metal atoms by incorporation into semiconductor lattice, etching by a byproduct of hydrogen reduction of the precursor gas, and/or vaporization of intermediate compounds dragged by the precursor gas flow. This also implies an eventual limitation of the maximum nanowire length (<NUM>-<NUM>). The method of the invention mitigates this effect by placing a secondary semiconductor substrate covered with the same metal catalyst as the growth semiconductor substrate into the CVD-chamber. Said secondary semiconductor substrate is positioned with respect to the growth semiconductor substrate in such a way that the precursor gas flow reaches first said secondary substrate. In this way, the loss of metal atoms normally produced at the growth substrate is partially compensated by the arrival of intermediate compounds created at the secondary semiconductor substrate.

In a preferred embodiment of the synthesis method of the invention, step d) is performed at a temperature comprised between <NUM>-<NUM>, and more preferably between <NUM>-<NUM> for <NUM>-<NUM> minutes.

In another preferred embodiment of the synthesis method of the invention, the metal-semiconductor alloy droplets are exposed to a precursor gas flow for <NUM>-<NUM> minutes in step e).

In a preferred embodiment of the synthesis method of the invention, the mass of metal catalyst deposited on the secondary semiconductor substrate in step c) comprises a higher concentration than the mass of metal catalyst deposited on the growth semiconductor substrate in step b). Preferably, the concentration of metal catalyst deposited on the secondary semiconductor substrate is between <NUM>-<NUM> times higher than the concentration of metal catalyst deposited on the growth semiconductor substrate.

In another preferred embodiment of the synthesis method of the invention, said method further comprises performing the following steps:.

In yet another preferred embodiment of the synthesis method of the invention, the precursor gas comprises silicon tetrachloride (SiCl<NUM>), a mixture of hydrogen (H<NUM>) and silicon tetrachloride (SiCl<NUM>), silane (SiH<NUM>), disilane (Si<NUM>H<NUM>), dichlorosilane (SiH<NUM>Cl<NUM>), or any possible combination thereof.

In yet another preferred embodiment of the synthesis method of the invention, wherein the mechanical resonator sensor comprises a nanowire resonator, the growth semiconductor substrate crystal orientation is (<NUM>) to obtain nanowires aligned perpendicularly to the growth semiconductor substrate. Alternatively, if the mechanical resonator comprises a cantilever resonator attached to a nanowire, the growth semiconductor substrate crystal orientation is preferably (<NUM>) to obtain nanowires aligned with the longitudinal axis of the cantilever resonator, which is preferably oriented along a (<NUM>) crystal orientation.

In yet another preferred embodiment of the synthesis method of the invention, the growth and/or secondary semiconductor substrate/s comprise/s:.

In yet another preferred embodiment of the synthesis method of the invention, the metal catalyst comprises Au, Ag, Al, Bi, Cd, Co, Cu, Dy, Fe, Ga, Gd, In, Mg, Mn, Ni, Os, Pb, Pd, Pt, Te, Ti, Zn, or any combination thereof.

In yet another preferred embodiment of the synthesis method of the invention, the step/s of depositing a first and/or a second mass of a metal catalyst on the growth and/or secondary semiconductor substrate/s comprises vaporization, spin coating, or lithography. In this way, the metal catalyst can be deposited over the surface of the growth and/or secondary semiconductor substrate/s forming a layer or as localized metal spots.

A fourth object of the invention relates to the use of a device according to any of the embodiments herein described for controlling mass flow in printing, patterning, proteomic assays, and/or chemical reactions.

In order to provide a better understanding of the technical features of the invention, the referred <FIG> are accompanied of a series of numerical references which, with an illustrative and non-limiting character, are hereby represented:.

While aspects of the subject matter of the present disclosure may be embodied in a variety of forms, the following description and accompanying drawings are merely intended to disclose some of these forms as specific examples of the subject matter. Accordingly, the subject matter of this disclosure is not intended to be limited to the forms or embodiments so described and illustrated.

Unless defined otherwise, all terms of art, notations and other technical terms or terminology used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs.

As described in preceding paragraphs, one object of the present invention relates to a nanomechanical mass flow meter and controller device for precise quantitative control of liquid transport in open nanofluidic systems. To do so, said device comprises:.

As previously described, the expression "conducting liquid" will be herein understood as any liquid solution that contains ions, including any type of salt dissolved in water and ionic liquids.

In different embodiments of the device of the invention, the mechanical resonator sensor (<NUM>) can comprise, for instance, a cantilever resonator attached to a nanowire (see <FIG>), or a nanowire resonator (see <FIG>). In both cases, the nanowire acts as receiving means (<NUM>) and typically comprises a metal or semiconductor material and, more preferably, silicon (Si), germanium (Ge), silicon carbide (SiC), indium arsenide (InAs), indium phosphide (InP), gallium arsenide (GaAs), gallium phosphide (GaP), indium antimonide (InSb), gallium antimonide (GaSb), gallium nitride (GaN), indium nitride (InN), aluminum nitride (AIN), or any combination thereof.

The selecting means (<NUM>) comprises a piezoelectric actuator to excite the flexural modes of the mechanical resonator sensor (<NUM>). However, other actuation systems can also be employed in the context of the invention, such as optomechanical, electrostatic, capacitive, resistive or photothermal actuators.

The monitoring means (<NUM>) comprises a photodetector to detect nanoscale deflection of the mechanical resonator sensor (<NUM>). To do that, laser emission means (<NUM>), for example a fiber-coupled diode laser, emits a laser beam in such a way that said beam is reflected or backscattered by the mechanical resonator sensor (<NUM>) and focused on the photodetector (<NUM>) by laser focusing means (<NUM>), typically, a 10X objective. Said photodetector (<NUM>) can comprise a photodiode of two or four closely jointed segments, or an unsegmented photoreceiver coupled to a low noise transimpedance amplifier. However, other types of transduction systems can also be employed in the context of the invention, such as optomechanical, electrostatic, capacitive, or resistive transducers.

In a preferred embodiment of the device of the invention (see <FIG>), the power of the laser emitted by the laser emission means (<NUM>) is controlled with a variable attenuator (<NUM>'), preferably in the range from <NUM>µW to <NUM>µW, high enough to resolve the thermomechanical signal of nanowires at acquisition times equal or lower than <NUM> second but without inducing any observable optomechanical back-action effect. The polarization of said emitted laser beam is aligned with the longitudinal axis of the mechanical resonator sensor (<NUM>) by means of birefringence loops (<NUM>"), so that the backscattered intensity is maximize and, hence, transduction sensitivity. After this fiber stage, a triplet lens collimator (<NUM>‴) provides a nearly Gaussian free-space laser beam, with its optical axis oriented perpendicular to the longitudinal axis of the mechanical resonator sensor (<NUM>). Collimated laser beam is focused on the mechanical resonator sensor (<NUM>) using a 10X objective (<NUM>) with <NUM> numerical aperture, which results into a laser spot waist diameter of around <NUM>.

The reservoir (<NUM>) comprises a conductive support, preferably made of gold or platinum-iridium, and adapted for preferably containing one or more droplets of any of the following ionic liquids: <NUM>,<NUM>-dimethyl-<NUM>-propylimidazolium bis(trifluoromethylsulfonyl)imide, <NUM>-butyl-<NUM>-methylimidazolium tetrafluoroborate, or diethylmethyl(<NUM>-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide. The relative position of said reservoir (<NUM>) with respect to the receiving means (<NUM>) is controlled by an XYZ nanopositioning stage (<NUM>).

Imaging means (<NUM>), preferably a CCD camera with white light illumination, is coupled to the mechanical resonator sensor (<NUM>) to follow in real-time the approximation of the reservoir (<NUM>) to the receiving means (<NUM>) and, optionally, the deposition of a mass of conducting liquid (<NUM>') on said means (<NUM>).

The resulting electrical signal from the photodetector (<NUM>) is then processed by processing means (<NUM>), either a digital acquisition (DAQ) board or a lock-in amplifier (LIA). LIA reference signal is delivered to the selecting means (<NUM>) in case of driven vibrations. The DAQ board is synchronized both with a waveform generator (WFG), which can also be connected to the selecting means (<NUM>), and with positioning means (<NUM>), allowing the acquisition of the signal of the photodetector as the relative mechanical resonator sensor (<NUM>)-laser beam position is scanned. Measurements can be performed in diverse environmental conditions, including, but not limited to, high vacuum (~<NUM>-<NUM> mbar), and at substrate temperatures of around <NUM>.

A second object of the invention relates to a method for controlling mass flow in open nanofluidic systems by means of a device according to any of the embodiments herein described. Advantageously, the method comprises performing the following steps (see <FIG>):.

Additionally, said method can further comprises a step of determining a mass flow rate of conducting liquid, ṁL, along the receiving means (<NUM>) by dividing the mass of conducting liquid (<NUM>'), mL, by the period of time Δt.

In a preferred embodiment of the method of the invention, the voltage, in absolute value, applied by the dispensing means (<NUM>) is below <NUM> V (both polarities can produce controllable flow). Preferably, between <NUM> and <NUM> V and, more preferably, between <NUM> and <NUM> V, both in positive and negative values. Under these voltages, conducting liquid (<NUM>') from the reservoir (<NUM>) can be made to flow steadily along the receiving means (<NUM>) with both great degree of control and high flow rate measurement sensitivity (nanowire resonator: <NUM>-<NUM> ag/s, in vacuum; cantilever resonator attached to a nanowire: <NUM>-<NUM> fg/s, at standard temperature and pressure). Below <NUM>-<NUM> V, depending on the characteristics of the nanowire and the conducting liquid, liquid transport to the nanowires does not occur, and above <NUM>-<NUM> V, chemical reactions result in nanowire etching, preventing accurate measurement and control of the mass flow rate.

In yet another preferred embodiment of the method of the invention, the conducting liquid (<NUM>') loaded in the reservoir (<NUM>) comprises an ionic liquid and is subject to a pressure lower than <NUM> atm. More preferably, the pressure is maintained below <NUM> atm during the performance of the method of the invention, for example, by introducing the device inside a vacuum chamber. Under these conditions, the ionic liquid (<NUM>') does not evaporate, allowing not only controlling the mass flow of the ionic liquid (<NUM>') in an open nanofluidic system, but also measuring analytes within that liquid (<NUM>') without degrading them (e.g., proteins).

A third object of the invention relates to a synthesis method of semiconductor nanowires as receiving means (<NUM>) of a nanomechanical mass flow meter and controller device according to any of the embodiments herein described, based on vapor-liquid-solid mechanism for single-crystal growth. Advantageously, the method comprises performing the following steps in any technically possible order:.

In yet another preferred embodiment of the invention, the precursor gas comprises silicon tetrachloride (SiCl<NUM>), a mixture of hydrogen (H<NUM>) and silicon tetrachloride (SiCl<NUM>), silane (SiH<NUM>), disilane (Si<NUM>H<NUM>), dichlorosilane (SiH<NUM>Cl<NUM>), or any possible combination thereof.

Previously to step e), the chemical-vapor deposition-chamber is usually purged with an inert gas, and the precursor gas flow is stabilized. After step e), said chamber is usually purged again with an inert gas, not only to remove traces of the precursor gas, but also intermediate compounds generated during the chemical vapor deposition.

Steps b) and/or c) can be carried out by vaporization, spin coating, or lithography. In this way, the metal catalyst can be deposited over the surface of the growth and/or secondary semiconductor substrates forming a layer or as localized metal spots.

Unlike technological approaches known in the prior art, the method of the invention allows fabricating semiconductor nanowires up to <NUM> in length with controllable tapered morphology and orientation. Tapered cross-sectional semiconductor nanowires have been ascribed to a gradual decrease of the metal-semiconductor alloy droplets diameter during the nanowire growth process due to metal incorporation into semiconductor lattice, etching by a byproduct of hydrogen reduction of the gaseous silicon precursor, and/or metal vaporization dragged by the precursor gas flow. This also implies an eventual limitation of the maximum nanowire length (<NUM>-<NUM>). The method of the invention mitigates this effect by placing a secondary semiconductor substrate covered with the same metal catalyst as the growth semiconductor substrate into the CVD-chamber. Said secondary semiconductor substrate is positioned with respect to the growth semiconductor substrate in such a way that the precursor gas flow reaches first said secondary substrate. In this way, the loss of metal atoms normally produced at the growth substrate is partially compensated by the arrival of intermediate compounds created at the secondary semiconductor substrate.

In a preferred embodiment of the invention, the mass of metal catalyst deposited on the secondary semiconductor substrate in step c) comprises a higher concentration than the mass of metal catalyst deposited on the growth semiconductor substrate in step b). Preferably, the concentration of metal catalyst deposited on the secondary semiconductor substrate is between <NUM>-<NUM> times higher than the concentration of metal catalyst deposited on the growth semiconductor substrate.

Preferably, the growth semiconductor substrate crystal orientation is:.

The growth and/or secondary semiconductor substrate/s preferably comprise/s:.

In yet another preferred embodiment of the invention, the mass of metal catalyst deposited on the growth and/or the secondary semiconductor substrate/s in step b) and/or c) comprises Au, Ag, Al, Bi, Cd, Co, Cu, Dy, Fe, Ga, Gd, In, Mg, Mn, Ni, Os, Pb, Pd, Pt, Te, Ti, Zn, or any combination thereof.

This first example shows the process of depositing a mass of liquid in an open nanofluidic system by means of the device of the invention in one of its preferred embodiments following the method of the invention. Specifically, the mechanical resonator sensor (<NUM>) comprises a cantilever resonator (mr= <NUM> ng) attached to a nanowire, said nanowire acting as receiving means (<NUM>). The conducting liquid (<NUM>') loaded into the reservoir (<NUM>) is <NUM>,<NUM>-dimethyl-<NUM>-propylimidazolium bis(trifluoromethylsulfonyl)imide. Said process was carried out in air at <NUM>.

As shown in <FIG>, the process starts with the cantilever resonator under a mechanical resonance frequency (ω) of <NUM>. After putting the conducting liquid (<NUM>'), loaded into the reservoir (<NUM>), in contact with the nanowire (<NUM>) by an XYZ nanopositioning stage (<NUM>), a frequency shift (Δω) is caused since a mass of said conducting liquid (<NUM>') is deposited on the nanowire (<NUM>) by applying a voltage of <NUM> V between said reservoir (<NUM>) and the nanowire (<NUM>) for <NUM> seconds (Δt) with the dispensing means (<NUM>) (see <FIG>). To demonstrate the reproducibility of the method of the invention, this process was repeated <NUM> more times, represented by the stepwise reduction in the mechanical resonance frequency of the cantilever resonator in <FIG>. The amount of mass of conducting liquid deposited on the nanowire (<NUM>) during each repetition of the method of the invention is shown in <FIG> (mean ± standard deviation: mL = <NUM> ± <NUM> pg).

This second example shows the process of controlling liquid transport in an open nanofluidic system by means of the device of the invention in one of its preferred embodiments following the method of the invention. Specifically, the mechanical resonator sensor (<NUM>) comprises a cantilever resonator (mr= <NUM> ng) attached to a nanowire, said nanowire acting as receiving means (<NUM>). The conducting liquid (<NUM>') loaded into the reservoir (<NUM>) is <NUM>,<NUM>-dimethyl-<NUM>-propylimidazolium bis(trifluoromethylsulfonyl)imide. Said process was carried out in air at <NUM>.

The process starts with the cantilever resonator (<NUM>) under a mechanical resonance frequency of <NUM>. After putting the conducting liquid (<NUM>'), loaded into the reservoir (<NUM>), in contact with the nanowire (<NUM>) by an XYZ nanopositioning stage (<NUM>), a frequency shift (Δω) is caused since a mass of said conducting liquid (<NUM>') is deposited on the nanowire (<NUM>) by applying a constant voltage of <NUM> V between the reservoir (<NUM>) and the nanowire (<NUM>) with the dispensing means (<NUM>). The amount of mass of conducting liquid (<NUM>') deposited in the nanowire (<NUM>) as a function of the time that the conducting liquid (<NUM>') and the nanowire (<NUM>) are in contact and under voltage is shown in <FIG>, obtaining a controlled mass flow rate of conducting liquid (<NUM>') ṁL of <NUM> fg/s.

This third example shows liquid transport in an open nanofluidic system by means of the device of the invention in one of its preferred embodiments depending on the voltage applied by the dispensing means (<NUM>) between the reservoir (<NUM>) and the receiving means (<NUM>) of the mechanical resonator sensor (<NUM>). Specifically, the mechanical resonator sensor (<NUM>) comprises a cantilever resonator (mr = <NUM> ng) attached to a nanowire, said nanowire acting as receiving means (<NUM>). The conducting liquid (<NUM>') loaded into the reservoir (<NUM>) is <NUM>,<NUM>-dimethyl-<NUM>-propylimidazolium bis(trifluoromethylsulfonyl)imide. Said process was carried out in air at <NUM>.

The process starts with the cantilever resonator under a mechanical resonance frequency (ω) of <NUM>. After putting the conducting liquid (<NUM>'), loaded into the reservoir (<NUM>), in contact with the nanowire (<NUM>) by an XYZ nanopositioning stage (<NUM>), an increasing voltage between the reservoir (<NUM>) and the nanowire (<NUM>) is applied by the dispensing means (<NUM>). As shown in <FIG>, liquid transport to the nanowire (<NUM>) does not occur below <NUM> V, and above <NUM> V approx. , chemical reactions result in nanowire etching, preventing accurate measurement and control of the conducting liquid mass flow rate.

This forth example shows the process of depositing a mass of liquid in an open nanofluidic system by means of the device of the invention in one of its preferred embodiments following the method of the invention. Specifically, the mechanical resonator sensor (<NUM>) comprises a nanowire resonator (mr=<NUM> fg), wherein a controlled mass of conducting liquid (<NUM>') will be deposited. The conducting liquid (<NUM>') loaded into the reservoir (<NUM>) is <NUM>,<NUM>-dimethyl-<NUM>-propylimidazolium bis(trifluoromethylsulfonyl)imide. Said process was carried out in in high vacuum (<NUM>-<NUM> mbar) at a temperature of <NUM>.

As shown in <FIG>, the process starts with the nanowire resonator under a mechanical resonance frequency (ω) of <NUM>. After putting the conducting liquid (<NUM>'), loaded into the reservoir (<NUM>), in contact with the nanowire resonator by an XYZ nanopositioning stage (<NUM>), a frequency shift (Δω) is caused since a mass of said conducting liquid (<NUM>') is deposited on the nanowire resonator by applying a voltage of <NUM> V between the reservoir (<NUM>) and the nanowire resonator for <NUM> seconds (Δt) with the dispensing means (<NUM>) (see <FIG>).

To demonstrate the reproducibility of the method of the invention, this process was repeated <NUM> more times, represented by the stepwise reduction in the mechanical resonance frequency of the nanowire resonator in <FIG>. The amount of mass of conducting liquid (<NUM>') deposited on the nanowire resonator during each repetition of the method of the invention is shown in <FIG> (mean ± standard deviation: mL = <NUM> ± <NUM> ag).

This fifth example shows the process of controlling liquid transport in an open nanofluidic system by means of the device of the invention in one of its preferred embodiments following the method of the invention. Specifically, the mechanical resonator sensor (<NUM>) comprises a nanowire resonator (mr= <NUM> fg), wherein a controlled mass of conducting liquid (<NUM>') will be deposited. The conducting liquid (<NUM>') loaded into the reservoir (<NUM>) is diethylmethyl(<NUM>-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide. Said process was carried out in in high vacuum (<NUM>-<NUM> mbar) at a temperature of <NUM>.

The process starts with the nanowire resonator under a mechanical resonance frequency (ω) of <NUM>. After putting the conducting liquid (<NUM>'), loaded into the reservoir (<NUM>), in contact with the nanowire resonator by an XYZ nanopositioning stage (<NUM>), a frequency shift (Δω) is caused since a mass of said conducting liquid (<NUM>') is deposited on the nanowire resonator by applying a voltage of <NUM> V between the reservoir (<NUM>) and the nanowire resonator with the dispensing means (<NUM>). The amount of liquid mass deposited in the nanowire resonator as a function of the time that the conducting liquid (<NUM>') and the nanowire resonator are in contact and under voltage is shown in <FIG>, obtaining a controlled mass flow rate of conducting liquid ṁL of <NUM> ag/s.

This sixth example shows liquid transport in an open nanofluidic system by means of the device of the invention in one of its preferred embodiments depending on the voltage applied by the dispensing means (<NUM>) between the reservoir (<NUM>) and the receiving means (<NUM>) of the mechanical resonator sensor (<NUM>). Specifically, the mechanical resonator sensor (<NUM>) comprises a nanowire resonator (mr= <NUM> fg), wherein a controlled mass of conducting liquid (<NUM>') will be deposited. The conducting liquid (<NUM>') loaded into the reservoir (<NUM>) is diethylmethyl(<NUM>-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide. Said process was carried out in in high vacuum (<NUM>-<NUM> mbar) at a temperature of <NUM>.

Claim 1:
Nanomechanical mass flow meter and controller device comprising:
- a mechanical resonator sensor (<NUM>) comprising receiving means (<NUM>) adapted for receiving a mass of conducting liquid (<NUM>') disposed thereon, wherein said resonator sensor (<NUM>) possesses at least one mechanical vibration mode selectable in one or more working frequencies;
- selecting means (<NUM>) adapted for selecting a working frequency corresponding to one mechanical vibration mode of the mechanical resonator sensor (<NUM>);
- monitoring means (<NUM>) adapted for monitoring the mechanical spectra of the coupled system conformed by the mass of conducting liquid (<NUM>') and the mechanical resonator sensor (<NUM>);
and characterized in that said device further comprises:
- a reservoir (<NUM>) adapted for containing the mass of conducting liquid (<NUM>');
- positioning means (<NUM>) adapted for adjusting the relative position of the reservoir (<NUM>) with respect to the receiving means (<NUM>); and,
- dispensing means (<NUM>) adapted for dispensing the mass of conducting liquid (<NUM>') contained in the reservoir (<NUM>) on the receiving means (<NUM>), through the application of a voltage between the reservoir (<NUM>) and the receiving means (<NUM>).