JP2013527443A - Liquid evaporator - Google Patents

Abstract

  The present invention relates to a method and apparatus for evaporating at least part of a liquid 3, which is supplied through a duct 5 through an opening 4. The opening leads to a vapor chamber 9 maintained at a temperature higher than the evaporation temperature of the liquid 3. The liquid 3 is irradiated with an electromagnetic wave (laser 1) in the region of the opening so that at least a part of the liquid evaporates and the vapor enters the heated vapor chamber 9.

Description

  The present invention relates to a liquid evaporator and a method for evaporating a liquid.

  A liquid evaporator is used for converting a liquid into a gas phase, and is used in various applications.

  US7618027B2 discloses a liquid evaporator for producing, for example, a low vapor pressure high purity gas used in the field of microelectronics.

  WO05 / 016512A1 discloses a liquid evaporator that can be used, for example, in a method for removing volatile compounds from a substance mixture.

  Liquid evaporators are widely used in analysis, and the sample quantity of the liquid to be analyzed is first converted to a gas phase in order to be available for any analysis method. US7309859B2 discloses a liquid evaporator that can be used, for example, in an ion source for a mass spectrometer.

  Special requirements are imposed on liquid evaporators, especially in the analytical field. For example, in the case of quantitatively reliable analysis, it is important that the concentration of all components of the substance mixture in the gas phase is equal to the concentration in the liquid. For this purpose, it is necessary to completely evaporate the sample volume. In order to avoid recondensation, the gaseous sample then needs to be transported to an analytical system, for example, at a temperature above the maximum evaporation temperature of the components involved.

  To date, liquid evaporators have been suitably configured as continuous heated systems in which liquid samples are continuously supplied in small portions. In order to evaporate a plurality of components having different evaporation temperatures completely and simultaneously as much as possible, the evaporator's high heat capacity and high thermal mass are usually required. This inevitably requires high energy, and because of the generally spatially spread structure of the evaporator, requires much more power, sometimes incidentally between sampling and evaporation. Long dead time will also occur.

  Due to the improved performance of modern analytical systems, the amount of sample required for analysis has constantly decreased over time. For example, micro mass spectrometers that function with a minimum sample volume are known (see, for example, WO08 / 101669A1).

  On the one hand, a reduction in the amount of sample required is advantageous. A small sample amount means, for example, a short evaporation time and therefore a high temporal resolution when recording changes in sample components.

  On the other hand, the liquid evaporator needs to accommodate a small sample volume in order to be able to fully exploit the benefits of a smaller sample volume.

  Therefore, based on the known prior art, the object is to provide a liquid evaporator and a liquid evaporation method that can reliably evaporate a small volume of liquid. The sample volume to be evaporated is in this context preferably less than 100 μl, particularly preferably less than 10 μl, more preferably less than 1 μl.

  The sample volume after evaporation must represent the liquid from which it was collected. Liquid evaporators must be economical to manufacture and use, require less energy for evaporation, and ensure rapid evaporation. And the liquid evaporator should have a self-cleaning function or be configured as a disposable product so as to be able to evaporate liquids containing dissolved substances that can settle. .

  According to the invention, the above object is achieved by the method for evaporating at least a part of the liquid of claim 1 and by the liquid evaporator of claim 4 formed for carrying out this method.

Therefore, the present invention firstly is a method for evaporating at least a part of a liquid,
Liquid is supplied through the channel through the opening, which opens into a vapor chamber maintained at a temperature higher than the evaporation temperature of the liquid,
A method is provided wherein the liquid is irradiated with electromagnetic radiation in the region of the opening so that at least a portion of the liquid evaporates and vapor enters the heated vapor chamber.

The present invention secondly,
A channel and a vapor chamber are formed which are connected to each other via an opening, the channel allowing liquid to be supplied through the opening and an evaporation region adjacent to the opening optionally A main body configured to be irradiated with electromagnetic waves, including an opening, and
And a means for heating the vapor chamber.

  The method of the present invention and the evaporator of the present invention use electromagnetic energy to evaporate a liquid sample volume by local heating. For this purpose, the liquid passes through a channel leading to the chamber through the opening. The area of the opening is accessible for electromagnetic waves. That is, the region can be irradiated with electromagnetic waves. In this region (hereinafter also referred to as an evaporation region), the liquid is locally heated by electromagnetic waves to such an extent that the sample amount evaporates. The evaporated sample volume enters the chamber (hereinafter also referred to as the evaporation chamber) through the opening, which can be heated to a temperature higher than the evaporation temperature of the liquid, Does not condense.

  The electromagnetic waves are preferably supplied from outside the liquid evaporator to the evaporation site. Therefore, it is preferred that the evaporation site comprises a cover that is at least partially transparent to the electromagnetic waves in use. A cover that is at least partially transparent is a cover that transmits most of the electromagnetic waves and absorbs and / or reflects only a small portion of it, where most of the incident energy reaches the evaporation site, where any Available to heat sample volume. The high permeability (translucency) of the cover, and hence low absorption, has the effect that the cover itself is not heated.

  Preferably, the evaporation region is configured to absorb electromagnetic waves at a high rate and convert the absorbed electromagnetic waves into heat. For example, the inner wall of the channel is made of a material that absorbs most of the incident energy and turns it into heat. Similarly, it is also conceivable to coat the inner wall of the channel with a material having a high absorption coefficient for electromagnetic waves in use in the evaporation region. In both cases it is also possible for the evaporator to evaporate a liquid which itself has a low absorption coefficient for the electromagnetic waves in use (heating is performed indirectly). The evaporating zone is also referred to below as an absorber when it is adapted for indirect liquid heating.

  However, the radiation source used is conveniently adapted to the liquid to be evaporated so that the liquid can be heated directly. Direct heating has the advantage that the liquid environment (ambient atmosphere) is only slightly heated, thus minimizing adverse effects on the analysis (temporary resolution degradation, contamination, damage, etc.) from the heated environment. .

  Preferably, a laser beam is used for irradiation. It is particularly preferred to use a focused, pulsed laser beam. Preferably, the laser pulse length is selected so that the thermal time constant of at least one of the absorber and the liquid to be evaporated is longer than the laser pulse length. This means that a single pulse is sufficient to evaporate any sample volume.

  The amount of liquid that evaporates can be changed by changing the laser pulse length and by changing its power. A pulse train may be used for larger amounts of evaporation. Since the instant of evaporation can be established very accurately, the generation of vapor can be synchronized with the sampling in the analyzer, allowing correlation measurements with high measurement sensitivity. In addition, this method allows the sample stream to be evaporated in segments and analyzed in a controlled manner so that it can be carried by a sample composition or liquid that varies greatly with time. Unmixed or undissolved components (emulsions, cells) can also be recorded in a defined or selective manner.

  The laser beam is supplied by a free beam or fiber optics through a cover that is at least partially transparent to the laser beam.

  The transition from the channel to the vapor chamber is configured such that liquid cannot freely flow into the vapor chamber due to the capillary force at the opening. Suppression of liquid discharge is achieved by the fact that the dimension of the cross section of the chamber at the location of the opening is sufficiently different from the length and cross section of the interface with the channel. As an alternative or in addition, the inner wall of the channel and the chamber may be provided with layers having different surface energies, at least in the region of the opening. If the liquid to be evaporated is an aqueous solution, for example, the open area of the channel can be provided with a hydrophilic coating and the open area of the chamber can be provided with a hydrophobic coating.

  The channel has a curvature in the evaporation region to allow sampling from the center of the channel, especially in the case of laminar flow with a small cross section and therefore non-turbulent flow. preferable. Due to the curvature, the flow rate in the inner and outer curved regions will be different. Dean vortices are generated, resulting in a flow perpendicular to the flow direction, carrying liquid elements from the center of the channel to the channel edge in the open region.

  Since the lightly heated position is always washed away with the following liquid, it is also possible to achieve the effect that solids precipitated during evaporation are redissolved or mechanically removed by the liquid stream and carried away. Dean vortices generated in the curved region of the channel aid this self-cleaning process.

  The evaporation chamber has a gas outlet. Vapor exits the evaporator of the present invention through this gas outlet. In addition to the gas outlet, this vapor chamber evacuates the vapor chamber between samplings to avoid cross-contamination of the sample from one evaporation process to the next, and optionally further A connection may be provided that allows the steam chamber to be flushed with water.

  As an alternative, this may each be done in a controlled manner after multiple evaporations. This is to increase at least one of the available gas volume or its pressure for injection, or to be able to average the sample volumes immediately prior to analysis.

  The steam chamber may be heated, preferably by an electrically operated heating element.

  In order to keep the steam uniformly hot, a lamellar structure made of a thermally conductive material may preferably extend (extend) into the steam chamber. The vapor chamber is heated locally by surface contact heating, and these lamellar structures are also heated by a heating device via heat conduction.

  The lamellar structure also facilitates evaporation of droplets carried by the vapor from the channel into the chamber.

  The lamellar structure is suitably applied to prevent particles from passing through the gas outlet (see FIG. 2), i.e. to block the opening and the gas outlet from each other.

  The energy input for the evaporation takes place optically, i.e. contactlessly, and the heating of the chamber does not have to be incorporated directly into it, so this evaporation system is simple to manufacture and in principle is contaminated. In this case, it can be easily replaced. In a preferred embodiment, the liquid evaporator according to the present invention is configured as a disposable item.

  The main body of the liquid evaporator according to the present invention, in which the channel and the chamber are formed, can be composed of one piece (seamless) or a plurality of pieces. Preferably, it is composed of a one-piece (seamless).

  The liquid evaporator is preferably a microsystem and its structure is manufactured by microfabrication technology.

  The manufacture of structures in microsystems is known to those skilled in the microsystem art. Microfabrication techniques are described, for example, in the document “Fundamentals of Microfabrication” (Marc Madou, CRC Press Boca Raton FLA 1997) or in the document “Mikrosystemtechnik fuer Ingenieure [Microsystem technology for engineers] (W. Menz. J. Mohr, O. Paul, Wiley). -VCH, Weinheim 2005) For a more detailed description of silicon-on-silicon technology, see, for example, Q.-Y. Tong, U. Goesele: Semiconductor Wafer Bonding: Science and Technology; Located in the Society Series, Wiley-Verlag, New York (1999) For an example of glass-on-glass technology, see J. Wie et al., Low Temperature Glass-to-Glass Wafer Bonding. , IEEE Transactions on advanced packaging, Vol. 26, No. 3, 2003, pages 289-294; and Duck-Jung Lee et al., Glass-to-Glass Anodic Bonding for High Vacuum Packaging of Microelectronics and its Stability, MEMS 2000 , The Thirteenth Annual International Conference on Micro Electro Mechanical Systems, 23-27 January 2000, pages 253-258.

  Microsystem technology is basically a silicon substrate having a high aspect ratio (eg, very deep (˜100 μm), narrow (˜μm) trench) and structuring accuracies in the micrometer range and / or Or based on glass substrate structuring and combining a wet chemical, preferably a plasma etching process, with a sodium-containing glass substrate (eg Pyrex®) adapted in terms of thermal expansion coefficient. Use. These substrates have a simple etching structure and are directly connected to each other by a hermetic seal by so-called anodic bonding or connected by a thin film Au layer functioning as a solder alloy (AuSi).

  High aspect ratio metal structures can be produced with equivalent accuracy by electrolytic growth in thick photoresist (> 100 μm) (UV-LIGA). By using thin film technology such as high vacuum deposition and sputtering, PVD method, or chemical vapor deposition (CVD method) (preferably with plasma) in combination with photolithography and etching technology, metal wiring (metallization) Functional layers, such as hydrophilic or hydrophobic surfaces, and functional elements such as valve seals, diaphragms, heating elements, temperature sensors, pressure sensors, flow sensors, etc., on these substrates with fully process compatible technology Can be integrated.

  The liquid evaporator structure of the present invention is preferably manufactured with silicon-on-glass technology. Here, silicon is used for the body and glass is used for the transparent cover. This combination (preferably hermetically connected by anodic bonding) allows very precise structuring of the various components of the system, especially in silicon (photoetch technology, DRIE, coating). Silicon is stable both chemically and thermally like glass, and unlike glass, it is a good thermal conductor with a small heat capacity (heated chamber at a uniform temperature) and good for conventional laser wavelengths. Light absorber. The heat loss due to dissipation through the glass substrate is low.

  The combination of silicon and glass makes it possible to achieve local input of light energy into the edge of the channel and thermal separation (decoupling) between the channel and the vapor chamber. For thermal separation (decoupling), it is preferred that the vapor chamber and the liquid sample channel are separated by horizontal and vertical cuts in a highly thermally conductive heat conductor. Mechanical stability with low thermal conductivity is ensured by a transparent cover made of, for example, glass or polymer.

  It is also conceivable to make the liquid evaporator according to the invention from a polymer material, for example by injection molding techniques. Preferably, a composite material for the main body, for example, a polymer in which carbon (carbon black, carbon nanotube) is dispersed in order to improve electromagnetic wave absorption and thermal conductivity is used.

  Thanks to conventional dimensions in microsystem technology (ranging from tens to hundreds of μm), the system thus produced is suitable for the analysis or production of small sample volumes (nl liquid, μl in gas phase). Especially suitable for.

  In order to evaporate such a small sample volume, only low laser energy in the mW range is required, even for liquids with high evaporation enthalpies, such as water. These low laser energies are supplied with the required short pulse durations (eg 1 W for 1 ms) by standard semiconductor lasers (wavelength range eg 400 nm to 980 nm) coupled by fibers or lenses. 100 mW for 10 ms).

  The sample volume to be evaporated is preferably less than 100 μl, particularly preferably less than 10 μl, more preferably less than 1 μl.

  The liquid evaporator of the present invention is preferably suitable as a sample evaporator in a microanalysis system. Therefore, the present invention is a method of using the liquid evaporator of the present invention, for example, the document `` Complex MEMS: A fully integrated TOF micro mass spectrometer (Sensors and Actuators A: Physical, 138 (1) (2007), pages 22-27)) "are also provided, characterized in that they are used for microanalysis systems, in particular for use in micromass spectrometers or microgas chromatographs.

The liquid evaporator of the present invention and the liquid evaporation method of the present invention ensure the following points.
• Simultaneous evaporation of liquid and liquid mixture • Reliable evaporation of small volumes (preferably even if <1 μl)
• Short wasted time between evaporation of two samples • Rapid evaporation can achieve high time resolution during analysis • Typical sample evaporation • Low energy requirements for evaporation • Low equipment costs • High evaporation Suitable for media with enthalpy ・ Suitable for media containing dissolved solids (evaporation residue, precipitate) ・ Economic operation (manufacturing and replacement)
・ Low cost for peripheral equipment ・ Sampling that can be synchronized with sample analysis (lock-in principle)
・ Doseability of gas volume
-Adjustability of propellant gas pressure-Synchronization and averaging with multiple pulses-Statistical selection of samples to average (time window)
・ Average in gas space ・ Self-cleaning

  Hereinafter, the present invention will be described in more detail with reference to the drawings, but not limited thereto.

It is the perspective view which looked at the liquid evaporator of this invention from the upper direction. The state where the lamellar structure 12 is introduced into the chamber 9 of the liquid evaporator of FIG. 1 is shown. It is the sectional view on the AB line of the liquid evaporator of FIG.

  FIG. 1 is a perspective view of a liquid evaporator according to the present invention as viewed from above. The liquid evaporator includes a main body 6 in which a channel 5 and a chamber 9 are formed. The channel 5 and the chamber 9 are connected to each other through the opening 4. The channel 5 has a curvature 10 in the region of the opening 4. Liquid is supplied through channel 5 and through opening 4.

  The transition from the opening 4 to the chamber 9 is configured such that liquid cannot flow directly into the adjacent region 9 due to capillary forces in the opening 4.

  In the region of the opening, the liquid is irradiated with electromagnetic waves and heated. In this case, irradiation is performed from the direction of the observer (from above).

  The liquid is heated by irradiation, and a part of it evaporates. A portion of this enters the chamber 9 through the opening 4 as a vapor stream. Below the chamber 9 is a heating element, which can heat the steam chamber 9 (not shown in FIG. 1, see FIG. 3).

  The vapor chamber 9 and the liquid sample channel 5 are thermally separated by horizontal incisions 14 in the body 6 with high thermal conductivity.

  FIG. 2 shows the lamella structure 12 introduced into the chamber 9 of the liquid evaporator of FIG. The lamellar structure is heated through heat conduction by a heating element below the vapor chamber 9 (not shown in FIG. 2, see FIG. 3).

  FIG. 3 is a cross-sectional view of the liquid evaporator in FIG. 1 taken along line AB. In addition to the components already described in connection with FIG. 1, the transparent cover 2 that extends over the entire body 6 can be seen in FIG. 3. Furthermore, a heating element 8 is provided below the steam chamber 9. Irradiation of the liquid is preferably performed by the focused laser beam 1 through the transparent cover 2.

DESCRIPTION OF SYMBOLS 1 Electromagnetic wave 152 Transparent cover 3 Liquid 4 Opening 5 Channel 6 Main body 207 Vapor flow 8 Heating element 9 Vapor chamber 10 Curvature 11 Cross flow 2512 Lamellar structure (layered structure)
13 Gas outlet 14 Notch 16 Connection

Claims (10)

A method for evaporating at least a portion of a liquid,
The liquid is supplied through an opening through a channel, the opening leading to a vapor chamber maintained at a temperature higher than the evaporation temperature of the liquid,
The method wherein the liquid is irradiated by electromagnetic waves in the area of the opening so that at least a portion of the liquid evaporates and vapor enters the heated vapor chamber. The method of claim 1, wherein
Heating is performed by a focused pulsed laser beam. The method according to claim 1 or 2, wherein
A method characterized in that the liquid is a mixture. A channel and a vapor chamber are formed which are connected to each other via an opening, the channel allowing liquid to be supplied through the opening and an evaporation region adjacent to the opening optionally A main body configured to be irradiated with electromagnetic waves including an opening;
Means for heating the vapor chamber. The liquid evaporator according to claim 4.
The liquid evaporator, wherein the evaporation region includes a cover that is at least partially transparent to electromagnetic waves in use. The liquid evaporator according to claim 4 or 5,
The channel, the opening, and the evaporation region are configured such that liquid flowing through the channel remains in the channel due to at least one of capillary force and interface energy and does not flow freely into the vapor chamber. A liquid evaporator. The liquid evaporator according to any one of claims 4 to 6,
The liquid evaporator, wherein the channel has a curvature in the region of the opening, the curvature creating a Dean vortex in the flowing liquid. The liquid evaporator according to any one of claims 4 to 7,
A gas outlet in the steam chamber;
A connection in the steam chamber for venting air from the steam chamber and / or for flushing the steam chamber;
A liquid evaporation further comprising: a lamellar structure in the vapor chamber, connected in a thermally conductive manner to the means for heating the vapor chamber and arranged to block the gas outlet from the opening vessel. The liquid evaporator according to any one of claims 4 to 8,
A liquid evaporator manufactured as a silicon-on-glass technology microsystem, wherein silicon is used for the body and glass is used for the transparent cover.   Use of a liquid evaporator according to any one of claims 4 to 9, characterized in that it is used in a microanalysis system, in particular a micromass spectrometer or a microgas chromatograph.

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