Device And Method For Detecting A Concentration Of Predetermined Particles On The Basis Of Their Morphological Properties In Air

Abstract

A device (1) for detecting a concentration of predetermined particles, particularly viruses, in air (3) with organic and/or inorganic aerosol particles, has a supply unit (10), an imaging unit (20), an image acquisition unit (40) and an evaluation unit (50). The supply unit (10) binds the aerosol particles as particles in a fluid (4). The imaging unit (20) operates on the functional principle of a scanning electron microscope in order to generate an enlarged image of the particles contained in the fluid (4). The image acquisition unit (40) acquires and transmits the image. The evaluation unit (50) evaluates the particles depicted in the image. The evaluation unit (50) automatically detects morphological properties of the particles depicted in the image and compares the detected morphological properties with morphological properties of the predetermined particles. Through the comparison, it determines a proportion and/or number of predetermined particles in the image and the concentration of the predetermined particles in the air (3).

Claims

1. A device for detecting a concentration of predetermined particles, particularly viruses, in air that includes organic and/or inorganic aerosol particles, comprising: a supply unit, an imaging unit, an image acquisition unit, and an evaluation unit; the supply unit binds the aerosol particles contained in the air in a fluid, the fluid contains aerosol particles that were previously contained in the air as particles, and a constant or uniformly clocked fluid flow bypass along a predetermined flow path; the imaging unit has a sample channel, the interior can be flowed through by the fluid and determines the predetermined flow path within the imaging unit, and the imaging unit scans the particles in the fluid in the sample channel in a raster pattern using an electron beam as the primary electron beam, to capture electrons that are designated as secondary electrons through interaction of the electron beam with the particles and, by means of the captured electrons, to generate an enlarged image of the particles that are contained in the fluid flowing through the sample channel; the image acquisition unit acquires the image and transmit the image to the evaluation unit; and the evaluation unit automatically acquires morphological properties of the particles shown in the image, to compare the detected morphological properties with morphological properties of the predetermined particles, and to determine a proportion and/or a number of predetermined particles in the image and the concentration of the predetermined particles in the air by comparison.

2. The device as set forth in claim 1, wherein the imaging unit has a primary electron source that generates a primary electron beam, a plurality of magnets that direct the primary electron beam and act as a lens for the primary electron beam, at least one raster device for deflecting the primary electron beam in a raster pattern, a detector for detecting secondary electrons, and a vacuum chamber with a vacuum prevailing therein that is traversed by the primary electron beam, the sample channel passes through the vacuum chamber or adjoins the vacuum chamber and is arranged in or at the vacuum chamber in such a way that the primary electron beam strikes the sample channel and the fluid flowing through the sample channel, so that secondary electrons are generated.

3. The device as set forth in claim 1, wherein the sample channel is made at least partially of silicon nitride, aluminum foil, or another material that is permeable to the primary electron beam and to the secondary electrons and simultaneously seals the interior of the sample channel off from the vacuum chamber in a pressure-tight manner.

4. The device as set forth in claim 2, wherein the sample channel has a raster section on a side facing toward the primary electron beam over which the primary electron beam is deflected in a raster pattern by the raster device, and in the raster section, the sample channel is made of silicon nitride, aluminum foil, or another material that is permeable to the primary electron beam and to the secondary electrons that simultaneously seals the interior of the sample channel off from the vacuum chamber in a pressure-tight manner.

5. The device as set forth in claim 2, wherein the magnets embodied as permanent magnets or as electromagnets and supplied with a constant voltage, so that the primary electron beam is focused by the magnets in a single, predetermined manner on the fluid flowing through the sample channel, the sample channel is permanently connected to the vacuum chamber, the vacuum chamber is completely sealed in a pressure-tight manner and designed to permanently maintain a vacuum prevailing therein, so that a pressure reduction that determines the vacuum need only be carried out once.

6. The device as set forth in claim 2, wherein the raster device is designed to deflect the primary electron beam electrostatically and/or electromagnetically.

7. The device as set forth in claim 1, wherein the image acquisition unit is an A/D converter that converts an analog image acquired by secondary electrons by the detector into a digital image.

8. The device as set forth in claim 1, wherein the image acquisition unit and the imaging unit are integrally formed with one another, so that the particles in the sample channel are enlarged according to the principle of the scanning electron microscope and the enlarged image is captured according to the principle of an iconoscope, orthocon, or superorthicon.

9. The device as set forth in claim 1, wherein the evaluation unit has a data memory where the morphological properties and, in particular, an appearance of the predetermined particles are stored, and the evaluation unit determines, by image processing and object recognition, how many of the particles depicted in the figure have morphological properties and, in particular, an appearance corresponding to the morphological properties and, in particular, the appearance of the predetermined particles and are thus predetermined particles.

10. The device as set forth in claim 1, further comprising a radiation source for destroying particles, and particularly for destroying the predetermined particles, the radiation source aligned with the sample channel so that the particles in the sample channel can be destroyed.

11. A method for detecting a concentration of predetermined particles, particularly viruses, in air that comprises organic and/or inorganic aerosol particles, with a device according to claim 1, comprising: binding the aerosol particles contained in the air in a fluid using the supply unit so that the fluid contains the aerosol particles previously contained in the air as particles; generating a constant or uniformly clocked fluid flow along a predetermined flow path; the imaging unit generating an enlarged image of the particles that are contained in the fluid flowing through the sample channel; capturing the image with the image acquisition unit and transmitting the image to the evaluation unit; the evaluation unit automatically capturing morphological properties of the particles depicted in the image and comparing the captured morphological properties with morphological properties of the predetermined particles; and determining a proportion and/or a number of predetermined particles in the image and the concentration of the predetermined particles in the air by the comparison.

12. A system for determining a movement and concentration of predetermined particles in a space, comprising a central evaluation unit and a plurality of devices according to claim 1, and distributing the devices in the space according to a predetermined pattern and, in particular, according to a predetermined raster pattern, and the central evaluation unit uses the concentrations, respectively, determined by the devices generating a concentration of the particles in the space and/or a distribution of the predetermined particles in the space and/or to determining and/or predicting a movement of the predetermined particles in the space.

Description

DRAWINGS

[0063] Other advantageous refinements of the disclosure are characterized in the subclaims and/or depicted in greater detail below together with the description of the preferred embodiment of the disclosure with reference to the figures. In the drawing:

[0064] FIG. 1 is a schematic view of a first variant of the device.

[0065] FIG. 2 is a schematic view of a second variant of the device.

DETAILED DESCRIPTION

[0066] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0067] The figures are schematic examples. The same reference symbols in the figures indicate same functional and/or structural features.

[0068] The basic principle of the device 1 is to suck in or take in air 3 and, for example, ambient air at an air inlet 2, to bind the particles contained in the air 3 in the supply unit 10 in a liquid 4 as a fluid. Also, the principle provides a constant flow of liquid or fluid through the imaging unit 20. The flow can be both continuous and clocked. This enables an “in situ analysis” to be carried out on the particles that are bound in the liquid 4. Thus, the sample to be analyzed, which is the liquid 4, or, more precisely, the liquid 4 flowing through the imaging unit 20, is changed continuously or in a clocked manner. Together with the liquid 4, a constant flow of particles is provided through the SEM or through the imaging unit 20. The particles are imaged in an enlarged manner so that the particles contained in the sample or in the liquid 4 can be subsequently analyzed.

[0069] In the present case, the supply unit 10 has a pre-filter 11 where particles are filtered from the air 3 which, due to their size, charge, or other factors, cannot be the predetermined particles. For this purpose, the pre-filter 11 has a plurality of filtering stages and apply different filtering principles.

[0070] The air 3 filtered through the pre-filter 11 is condensed by a condenser 12. Thus, a condensate forms as a liquid 4 where the particles previously contained in the filtered air 3 are bound.

[0071] The condensate or the liquid 4 is then pumped along a predetermined flow path from the supply unit 10 into or through the imaging unit 20. A pump 60 arranged on the output side of the imaging unit 20 is used for this purpose.

[0072] In the liquid 4, the predetermined particles and all of the particles contained therein are initially distributed relatively uniformly. Thus, the sought-after or predetermined particles whose concentration is to be determined in the air are evenly distributed over a region of the liquid 4 and are difficult or time-consuming to find. To improve and simplify the analysis, the imaging unit 20 has an isotachophoresis device with a first voltage terminal 25 and a second voltage terminal 25′. The first voltage terminal 25 is fluidically arranged on the input side of the imaging unit 20 or of the sample channel 29. The and the second voltage terminal 25′ is fluidically arranged at the output side of the imaging unit 20 or of the sample channel 29. The terminals 25, 25 build up an electric field in the sample channel 29 so that the liquid 4 flowing through the sample channel 29 form a plurality of regions. Each region has particles with the same or approximately the same ion mobility. Substantially all particles with an ion mobility equal to the ion mobility of the predetermined particles and consequently substantially all predetermined particles are located in one of these regions. Thus, it is sufficient to image only this region using the imaging unit 20 or to capture the same using the image acquisition unit 40 or to evaluate the same using the evaluation unit 50.

[0073] The imaging unit 20 instantiated as a SEM does not have to be designed for different measurement methods or an exchanging of sample carriers or the like. Thus, the SEM is specialized for the present application. For this purpose, the SEM has a completely and permanently sealed vacuum chamber 31. A vacuum (high vacuum) was generated once and is permanently maintained in the chamber 31. A primary electron beam 30 is emitted into the vacuum chamber, which can also be referred to as a measuring column, by a primary electron source 21 and runs through the length of the vacuum chamber 31. The beam intensity of the primary electron beam 30 is invariably set by a Wehnelt cylinder 22. It is guided or focused onto the sample channel 29 by a fixed and non-adjustable aperture 23 and a plurality of magnets 26, 27. Additionally or alternatively, the Wehnelt cylinder 22 can also be supplied with a fixed, unchangeable voltage and thus adjusted. The intensity of the primary electron beam 30 is set and the primary electron beam 30 focused in a fixed manner. A scanning device 24 guides the primary electron beam 30 in a raster pattern over a predetermined raster section 34 of the sample channel 29 to generate an enlarged image of the sample that is arranged in the sample channel 29. The scanning device 24 deflects the primary electron beam 30 according to a predetermined pattern. Thus, it scans the sample according to the predetermined raster.

[0074] The liquid 4 flowing through the sample channel 29 is thus always struck by the primary electron beam 30 in a single, predetermined manner. The secondary electrons 33 are generated that strike the detector 32 of the SEM and generate an image of the particles present in the liquid 4.

[0075] The secondary electrons 33 captured by the detector 32 can be converted into an analog image. It can then be converted into a digital image. Alternatively, the secondary electrons 33 or the image represented by the same can be converted directly into a digital image by the image acquisition unit 40 without generating an analog image as an intermediate step. The digital image is then transmitted to the evaluation unit 50.

[0076] A section 5 of an image generated by an A/D converter 41 where a multitude of particles are visible is shown by way of example. In particular, four predetermined particles 42, 42′, 42″ are shown by way of example and are only partially or covertly visible. These can also be overlaid by other particles 43, 44. Furthermore, the external appearance 52 of a predetermined particle is stored in the evaluation unit 50 or the data memory 51 as a comparative image 6 or as a morphological property of the predetermined particles. With the aid of image processing, the particles in the section 5 of the image are now compared with the external appearance 52 of the target particle or of the predetermined particle. If there is a sufficiently high degree of correspondence with the comparative image 6, the respective analyzed particle in the section 5 is identified as a predetermined particle and counted. The predetermined particles or viruses can thus be distinguished from other particles by their external appearance or by their external shape. For example, even though the particle 43 is approximately the same size, so that it would be incorrectly recognized as a virus or predetermined particle if it were determined on the basis of size, it has a completely different contour or surface shape. Thus, it can be correctly identified as a virus or as a predetermined particle using the device proposed herein and classified as not being a predetermined particle or virus.

[0077] In FIG. 2, the imaging unit 20 and the image acquisition unit 40 are integrally formed with one another, for which reason the device 1 turns out to be an integration of a superorthicon and a SEM.

[0078] The basic structure of the device 1 according to FIG. 2 corresponds to that of a superorthicon, that is, to a vidicon with integrated evaluation (photomultiplier, electron multiplier) of the secondary electrons 33. The secondary electrons 33 are generated by the primary electron beam 30 according to the functional principle of a SEM.

[0079] Starting from a conventional superorthicon, the device 1 has a raster section 34 made of silicon nitride (SiN) instead of a glass window with a light-sensitive layer. The raster section 34 is embodied as a SiN plate having one or more regions (10 μm×10 μm) that can be referred to as windows. The thickness of the SiN plate or of the raster section 34, at least in the vicinity of the windows, is such that the primary electron beam 30 can reach the raster section 34 as far as the sample in the sample channel 29 directly adjoining the same to the rear and can scan it accordingly. A thickness of the “windows” that lies particularly in a range between 10 and 30 nm is advantageous for this purpose.

[0080] The rest of the construction of the device 1 or of the imaging unit 20 is selected such that resolutions of up to 10 nm and more are possible during imaging. This structure, which determines the resolution, is also determined particularly by the size of the raster section 34 and of the magnets 26, 27 for focusing.

[0081] In order to be able to provide the primary electron beam 30 with sufficient precision for the scanning or for the enlargement of the particles contained in the sample, the device 1 or the imaging device 20 can have additional electron lenses. It may include further magnets or coils 26, 27 that act as a lens for the primary electron beam 30.

[0082] In order to make fine adjustment possible, the present device has magnets or, in this case, coils 28 to adjust the primary electron beam 30. The structure is advantageously designed in such a way that anode voltages of up to 120 kV or more are possible.

[0083] The primary electron beam 30 generated by the Wehnelt cylinder 22 is deflected by the raster unit, formed particularly by the magnets or coils 24, according to a predetermined raster pattern. The beam 30 is guided over the raster section 34. As an alternative to deflection by coils, the raster unit can be designed to deflect the primary electron beam 30 electrostatically. The secondary electrons 33 generated as a result are then detected by the dynodes 36 as part of the photomultiplier and of the signal anode 37, which replace or form the detector 32 of the SEM.

[0084] The signal detected by the signal anode 37 is then amplified with the signal amplifier 38 and forwarded as an image signal 39 to the evaluation unit 50 (not shown in FIG. 2).

[0085] In order to be able to also determine, on the basis of the captured images, which of the particles in the image are the predetermined particles, the device 1 according to FIG. 2 has a radiation source 35. The radiation source 35 generates radiation that fragments the predetermined particles and thus destroys them. If the predetermined particles are viruses, the radiation source 35 generates UV light. The UV light causes the viruses to vibrate and thereby breaks them open. Thus, it is possible to determine which particles have been destroyed on the basis of a plurality of successively captured images. The destroyed or fragmented particles are the predetermined particles. Thus, the number in the images and the concentration in the air can be determined.

[0086] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.