A COLLECTING DEVICE AND A METHOD FOR COLLECTION OF AIRBORNE PARTICLES FROM A FLOW OF AIR

Abstract

A collecting device (200) for collecting airborne particles comprises: a first (202) and second layer (220) spaced apart for forming a particle collection chamber (240) therebetween, wherein inlets (210) extend through the first layer (202) for transporting a flow of air into the particle collection chamber (240); wherein ends (214) of the inlets (210) face a first surface (222) of the second layer (220) for capturing airborne particles by impaction; wherein outlets (230) extend through the second layer (220) for transporting the flow of air out of the particle collection chamber (240); wherein the inlets (210) and outlets (230) are staggered such that the center axes of the inlets (210) and outlets (230) are displaced from each other; wherein the flow of air experiences a pressure drop lower than 3 kPa at a flow rate of 0.5 liters per second, when the flow of air passes the collecting device (200).

Claims

1. A collecting device for collection of airborne particles from a flow of air, said collecting device comprising: a first layer and a second layer, wherein the first layer and the second layer are arranged to be spaced apart for forming a particle collection chamber between the first and the second layer, wherein the first layer comprises a plurality of inlets configured to extend through the first layer for transporting the flow of air therethrough into the particle collection chamber; wherein ends of the inlets are configured to face a first surface of the second layer for capturing airborne particles in the flow of air entering the particle collection chamber through the ends of the inlets by impaction of airborne particles on the first surface of the second layer; wherein the second layer comprises a plurality of outlets configured to extend through the second layer for transporting the flow of air therethrough out of the particle collection chamber; wherein the inlets and outlets are staggered such that the center axes of the inlets are displaced from the center axes of the outlets; wherein the collecting device is configured such that the flow of air experiences a pressure drop when passing the collecting device, the pressure drop being lower than 3 kPa at a flow rate of 0.5 liters per second.

2. The collecting device according to claim 1, wherein a volume of the particle collection chamber is smaller than 30 μl, such as smaller than 20 μl.

3. The collecting device according to claim 1, wherein the collecting device is configured such the pressure drop experienced by the flow of air when passing the collecting device is lower than 1.5 kPa at a flow rate of 0.5 liters per second.

4. The collecting device according to claim 1, wherein the collecting device is configured to provide a collection efficiency of at least 50% for particles having a diameter larger than 300 nm when the collecting device receives a flow of air with a flow rate of 0.5 liters per second.

5. The collecting device according to claim 1, wherein a smallest dimension of a cross-section of the inlets is in a range of 20-300 μm, such as in a range of 100-200 μm.

6. The collecting device according to claim 1, wherein a number of inlets is larger than 100, such as larger than 500, such as 1000-2000 inlets.

7. The collecting device according to claim 1, wherein a length of the inlets is in a range of 20-500 μm, such as in a range of 50-300 μm.

8. The collecting device according to claim 1, wherein a cross-section of the inlets is circular or rectangular.

9. The collecting device according to claim 1, wherein a smallest dimension of a cross-section of the outlets is in a range of 20-400 μm, such as in a range of 100-300 μm.

10. The collecting device according to claim 1, wherein a number of outlets is larger than 100, such as larger than 500, such as 1000-2000 outlets.

11. The collecting device according to claim 1, wherein a length of the outlets is in a range of 20-500 μm, such as in a range of 100-300 μm.

12. The collecting device according to claim 1, wherein the first layer and the second layer are spaced apart by a gap in a range of 10-150 μm, such as in a range of 20-100 μm.

13. The collecting device according to claim 1, wherein a projection of the inlets onto the first surface of the second layer form a hexagonal arrangement of the inlets surrounding each outlet.

14. The collecting device according to claim 1, wherein a projection of an inlet onto the first surface of the second layer is configured not to overlap with a closest neighbor outlet, such as a lateral separation of an edge of the projection of the inlet to an edge of the closest neighbor outlet being at least 20 μm.

15. A method for collection of airborne particles from a flow of air, said method comprising: receiving a flow of air onto a first layer of a collecting device, wherein the first layer comprises a plurality of inlets extending through the first layer; passing the flow of air through the inlets into a particle collection chamber between the first layer and a second layer of the collecting device spaced apart from the first layer; capturing airborne particles in the flow of air entering the particle collection chamber by impaction of airborne particles on a first surface of the second layer, wherein ends of the inlets are configured to face the first surface of the second layer; passing the flow of air out of the particle collection chamber through outlets extending through the second layer of the collecting device; wherein the inlets and outlets are staggered such that the center axes of the inlets are displaced from the center axes of the outlets; wherein the collecting device is configured such that the flow of air experiences a pressure drop when passing the collecting device, the pressure drop being lower than 3 kPa at a flow rate of 0.5 liters per second.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0086] The above, as well as additional objects, features and advantages of the present inventive concept, will be better understood through the following illustrative and non-limiting detailed description, with reference to the appended drawings. In the drawings like reference numerals will be used for like elements unless stated otherwise.

[0087] FIG. 1 is a schematic cross-sectional view of a sample collector including a collecting device for collection of airborne particles according to an embodiment.

[0088] FIG. 2 is a schematic cross-sectional view of a collecting device according to an embodiment.

[0089] FIG. 3 is a graph defining efficiency of capturing of particles through impaction and an explanatory cross-section of an inlet nozzle providing air flow for capturing particles through impaction.

[0090] FIGS. 4-5 are schematic views illustrating arrangement of inlets and outlets of the collecting device according to different embodiments.

[0091] FIGS. 6-8 are schematic cross-sectional views of the collecting device according to different embodiments.

[0092] FIG. 9 is a flowchart of a method according to an embodiment.

DETAILED DESCRIPTION

[0093] Referring now to FIG. 1, a collecting device 200 for collection of airborne particles from a flow of air is shown in relation to a sample collector 100. It should thus be realized that according to an embodiment, the collecting device 200 may be arranged in a sample collector 100 which provides an interface for allowing a flow of air from a human being to be provided through the collecting device 200. However, it should be realized that the collecting device 200 may be arranged to receive the flow of air in different manners and need not necessarily be mounted in a sample collector 100 or any other apparatus.

[0094] The sample collector 100 may be used for capturing airborne particles, such as aerosols and/or droplets in the flow of air exhaled by the human being. Thanks to capturing airborne particles, analysis of the airborne particles in the exhaled breath may be performed. This may be used for determining whether the human being carries a disease, which is spread through droplets and aerosols produced during normal breathing, talking, coughing, and sneezing. For instance, the capturing of airborne particles using the sample collector 100 may be used for screening whether a person is infected by influenza or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Thanks to the sample collector 100 capturing a sample based on an exhaled breath, the capturing of a sample from a person may be performed with minimal discomfort to the person.

[0095] The sample collector 100 may comprise a mouthpiece 102 to be inserted into the mouth of the person and through which the person exhales to provide a flow of air 104 through the sample collector 102.

[0096] The flow of air 104 may be guided through the sample collector 102 so as to pass the collecting device 200. The collecting device 200 is configured to capture airborne particles from the flow of air 104 through impaction in a particle collection chamber of the collecting device 200. The collecting device 200 may be configured to capture airborne particles with high efficiency and may further allow analysis of the collected airborne particles.

[0097] Analysis of the collected airborne particles may involve sample preparation by providing a reagent to the particle collection chamber for allowing reactions to take place in the particle collection chamber. The reactions may further be controlled by providing further influence on the particle collection chamber, such as by heating and/or cooling the sample in the particle collection chamber.

[0098] Furthermore, analysis of the collected airborne particles may be performed while the collecting device 200 is maintained in the sample collector 100. This implies that a risk of spreading of disease by opening of the sample collector 100 may be avoided.

[0099] Referring now to FIG. 2, the collecting device 200 according to an embodiment will be further described.

[0100] The collecting device 200 comprises a first layer 202 and a second layer 220. The first layer 202 and the second layer 220 are arranged to be spaced apart for defining a particle collection chamber 240 between the first layer 202 and the second layer 220.

[0101] The first layer 202 and the second layer 220 may each be formed from a semiconductor or semiconductor-based material, such as silicon or silicon dioxide. This may facilitate manufacturing of the collecting device 200, since small dimensions of the collecting device may be advantageously provided by semiconductor manufacturing processes.

[0102] The first layer 202 comprises a first surface 204 configured to receive a flow of air, which may be the flow of air 104 in the sample collector 100 as described above. The first layer 202 also comprises a second surface 206 facing the second layer 220. The first layer 202 further comprises a plurality of inlets 210 having a first end 212 at the first surface 204 of the first layer 202 and a second end 214 at the second surface 206 of the first layer 204.

[0103] The second layer 220 comprises a first surface 222 facing the first layer 202 and a second surface 224 at which the flow of air may be output from the collecting device 200 after having passed the collecting device 200. The second layer 220 further comprises a plurality of outlets 230 having a first end 232 at the first surface 222 of the second layer 220 and a second end 234 at the second surface 224 of the second layer 204.

[0104] The inlets 210 are configured to extend through the first layer 202 for transporting the flow of air 104 through the first layer 202 from the first end 212 to the second end 214. The second ends 214 of the inlets 210 are configured to face the first surface 222 of the second layer 220. Thus, when the flow of air 104 passes through the inlets 210, the flow of air 104 will impinge on the first surface 222 of the second layer 220 such that airborne particles may be collected on the first surface 222 of the second layer 220 and, hence, in the particle collection chamber 240, by impaction.

[0105] The particle collection chamber 240 has a first side 242 and a second side 244, wherein the first side 242 is defined by the second surface 206 of the first layer 204 and the second side 244 is defined by the first surface 222 of the second layer 220. The particle collection chamber 240 may further be defined by side surfaces formed in a spacer material 250 between the first layer 202 and the second layer 220.

[0106] The spacer 250 can either be a glue, double sided-adhesive tape, or in case of silicon/glass layers 202, 220, the spacer 250 can be integrated into one of the layer materials to enable anodic, fusion, or laser bonding of the first layer 202 and the second layer 220.

[0107] In another embodiment, not shown in FIG. 2, the inlets 210 may be configured to protrude from second surface 206 of the first layer 202 to extend further into the particle collection chamber 240. This may imply that the second ends 214 of the inlets 210 are closer to the first surface 222 of the second layer 220 so as to improve capturing of particles by impaction while ensuring that a volume of the particle collection chamber 240 is not too small.

[0108] The inlets 210 and the outlets 230 are arranged in a staggered arrangement. This implies that center axes of inlets 210 and outlets 230 are not aligned. Hence, the flow of air 104 passing through the inlets 210 into the particle collection chamber 240 will at least slightly change direction through the particle collection chamber 240 before the flow of air 104 may exit the particle collection chamber 240 through the outlets 230.

[0109] Thanks to the inlets 210 and the outlets 230 being staggered, the inlets 210 are arranged directly above the first surface 222 of the second layer 220 wherein capturing of airborne particles occur. The inlets 210 are arranged such that there is at least no opening in the first surface 222 of the second layer 220 corresponding to an outlet 230 at a projection of the center axes of the inlets 210 onto the first surface 222 of the second layer 220. As shown in FIG. 2, the inlets 210 and the outlets 230 are arranged such that the entire inlet 210 is projected on an area of the first surface 222 wherein no openings corresponding to outlets 240 are provided. Thus, airborne particles may be captured at the first surface 222 of the second layer 220, while the flow of air 104 through the inlets 210 changes direction to follow the first surface 222 and then escape the particle collection chamber 240 through the outlets 230.

[0110] As shown in FIG. 2, the inlets 210 may extend perpendicularly in relation to the first layer 202. Further, the outlets 240 may extend perpendicularly in relation to the second layer 220. With the first and second layer 202, 220 being parallel, this implies that the inlets 210 and the outlets 240 are parallel, arranged with the central axes displaced in relation to each other. This is a suitable arrangement for ensuring that the inlets 210 and outlets 240 are staggered and that the flow of air 104 is forced to change direction through the collecting device 200.

[0111] Thanks to the flow of air 104 being forced to change direction, momentum of airborne particles having a certain size will cause the airborne particles not to follow the flow of air 104 in its change of direction and instead the particles will be captured on the collection surface formed by the first surface 222 of the second layer 220. The capturing of airborne particles may involve capturing of aerosols but may also or alternatively involve capturing of larger droplets in the flow of air.

[0112] Collection of particles in the collecting device 200 is further illustrated in the enlarged insert A of FIG. 2, illustrating that airborne particles will be captured by impaction on the first surface 222 of the second layer 220, before the flow of air 104 proceeds to outlets 230 extending through the second layer 220.

[0113] The collecting device 200 may further be configured to provide optical access for performing a measurement, based on light, of airborne particles collected in the particle collection chamber 240.

[0114] The measurement may be performed based on light that is passed through at least one of the first and second layers 202, 220. Thus, the first layer 202 and/or the second layer 220 may be transparent or translucent to provide optical access to the particle collection chamber 240. However, according to another embodiment, optical access is provided through the inlets 210 and/or the outlets 230.

[0115] In addition to the inlets 210 and outlets 230, a liquid access port 260 providing a reagent inlet may be provided in the collecting device 200. The liquid access port 260 may extend through the first layer 202 as shown in FIG. 2, but may alternatively extend through the second layer 220 instead. The liquid access port 260 enables filling of the particle collection chamber 240 with a liquid reagent, such as a polymerase chain reaction (PCR) reagent.

[0116] The collecting device 200 may further be configured to allow a sample in the particle collection chamber 240 to be heated and/or cooled, possibly in numerous iterations, in order to prepare the sample for analysis. For instance, thermal energy may be provided to the particle collection chamber 240 for thermal lysis to expose RNA of SARS-CoV-2 in the captured particles, converting the RNA to DNA using reverse transcriptase based on the reagent and providing thermal cycling for amplification of the DNA using quantitative PCR.

[0117] Referring now to FIG. 3, design of the collecting device 200 for providing an efficient capturing of particles will be discussed.

[0118] FIG. 3 is based on a figure from Marple and Willeke, “Impactor Design”, Atmospheric Environment, vol. 10 (10), 1976, pp. 891-896.

[0119] The collection efficiency, the percentage of particles that will impact the plate, is a strong function of the Stokes number and Reynolds number. The Stokes number is defined as:

[00001]$\mathrm{Stk}=\frac{4{\rho }_p{\mathrm{QC}}_c{d}_p^2}{9\pi N{\mu }_g{W}^3}$

where ρ.sub.p is the density of the particle, Q is the total volumetric flow rate for an array of inlets, C.sub.c is the Cunningham correction factor (taken as 1 for all subsequent calculations), d.sub.p is the particle diameter, N is the number of inlets in the array, μ.sub.g is the dynamic viscosity of air, and W is the inlet diameter. For the above study, distances T and S as indicated in FIG. 3 are T=2 W and S=W/2. The Reynolds number is defined as:

[00002]$\mathrm{Re}=\frac{4{\rho }_{p}Q}{\pi N{\mu }_{g}W}$

[0120] According to the FIG. 3, in order to capture 50% of the particles at a Reynolds number of Re=100, then

[00003]$\sqrt{\frac{4{\rho }_p{\mathrm{QC}}_c{d}_p^2}{9\pi N{\mu }_g{W}^3}}\approx 0.48.$

Note that for increasing particle diameters, √{square root over (Stk)} increases and higher collection efficiencies are obtained. Conversely, small particles are more difficult to capture than large particles.

[0121] According to an embodiment, the collecting device 200 is intended to be used for collecting a sample from exhaled breath from a person and then perform subsequent analysis on the collecting device 200 to screen for possible infectious disease(s). The analysis, for instance, could be end-point or quantitative reverse transcriptase polymerase chain reaction (RT-PCR) for an RNA virus like SARS-CoV-2.

[0122] It is desired to have a high collection efficiency of approximately 50% for particle diameters down to 300 nm. This is to ensure that enough sample can be collected to have reasonably sensitive results for detection of the biological agent of interest from a reasonably small sampling of exhaled breath from the patient.

[0123] Furthermore, it is intended that the person exhales through the collecting device 200. In order to ensure that the person can properly blow through the collecting device 200 without discomfort, the collecting device 200 is designed such that the pressure drop experienced by the flow of air 104 when passing through the collecting device 200 is lower than 3 kPa at a flow rate of 0.5 liters per second. Further, the person that is to exhale through the collecting device 200 may suffer from disease such that the person has a shortage of breath. In this respect, the collecting device 200 is preferably designed such that the pressure drop experienced by the flow of air 104 when passing through the collecting device 200 is lower than 1.5 kPa at a flow rate of 0.5 liters per second.

[0124] The desired pressure drop to be provided through the collecting device 200 may be used for designing the collecting device 200. Thus, dimensions of the collecting device 200 may be set in order to ensure that the pressured drop is within the desired range.

[0125] The pressure drop is dependent on dimensions of airway channels (inlets 210, particle collection chamber 240 and outlets 230) through which the flow of air 104 passes when passing the collecting device 200. However, the inlets 210 are also designed in order to provide a desired collection efficiency of particles in the particle collection chamber 240. Further, the particle collection chamber 240 may also be designed such that the volume of the particle collection chamber 240 is relatively small. The small volume of the particle collection chamber 240 facilitates performing fast analysis of a sample in the particle collection chamber 240.

[0126] The particle collection chamber 240 may typically be filled with a reagent after collection of particles in the particle collection chamber 240. Then, the sample in the particle collection chamber 240 may need to be heated and/or cooled, possibly in numerous iterations, in order to prepare the sample for analysis. Having a small volume of the particle collection chamber 240 implies that steps of heating and/or cooling the sample in the particle collection chamber 240 may be quickly performed.

[0127] Thus, the collecting device 200 may further be designed such that the volume of the particle collection chamber 240 is smaller than 30 μl. Preferably, the volume of the particle collection chamber 240 should be smaller than 20 μl.

[0128] Further, the collecting device 200 may further be designed to provide a collection efficiency of at least 50% for particles having a diameter larger than 300 nm when a flow rate the flow of air 104 passing the collecting device 200 is 0.5 liters per second.

[0129] The collecting device 200 is configured to meet at least the requirement relating to pressure drop being less than 3 kPa for a flow rate of the flow of air 104 of 0.5 liters per second, but is preferably also configured to meet the requirement relating to volume of the particle collection chamber 240 being smaller than 30 μl and the requirement relating to the collection efficiency.

[0130] The smallest dimension of a cross-section of the inlets 210 may be in a range of 20-300 μm. Preferably, the smallest dimension of the cross-section of the inlets 210 is in a range of 100-200 μm.

[0131] The size and shape of the inlets 210 may be set in relation to at least a desired efficiency of collection of particles, since the inlets 210 highly affect the efficiency of collection of particles. Then, other features of the collecting device 200 may be related to the size and shape of the inlets 210 such that at least the desired pressure drop is provided.

[0132] As indicated in the above discussion, the smallest dimension of the cross-section of the inlets 210 needs to be small in order to provide efficient collection of particles having a small diameter. However, a small dimension of the cross-section of the inlets 210 may imply that a large pressure drop is provided.

[0133] Using the smallest dimension of the cross-section of the inlets in the range of 20-300 μm, and in particular in the range of 100-200 μm facilitates that the collecting device will provide a collection efficiency of at least 50% for particles having a diameter larger than 300 nm and also facilitates that the pressure drop in the flow of air passing the collecting device will be lower than 3 kPa, even lower than 1.5 kPa, at a flow rate of 0.5 liters per second.

[0134] The cross-section of the inlets 210 may be circular. This may be suitable for manufacturing of the collecting device 200. Also, it may ensure that a symmetric behavior of the flow of air 104 flowing through the inlets 210 is provided around the central axis of the inlet 210. For a circular cross-section, the smallest dimension of the inlet 210 is the diameter of the inlet 210. However, it should be realized that other shapes of the cross-section of the inlets 210 are conceivable. For instance, the inlets 210 may be rectangular and may even be in the form of elongate rectangular slits.

[0135] The number of inlets 210 used may control a total flow rate through the collecting device 200, and an associated pressure drop experienced by the flow of air 104. In view of the cross-sectional dimension of the inlets 210, the number of inlets 210 may be selected to provide a sufficient flow rate of air through the collecting device 200. With large inlets 210, each inlet 210 supports a relatively large flow rate, whereas small inlets 210 support a relatively small flow rate. Thus, the number of inlets 210 may need to be larger for smaller inlets 210.

[0136] Since the size of the inlets 210 is preferably small for a large collection efficiency as discussed above, the number of inlets 210 may need to be quite large, such as more than 100, or more than 500, such as in a range of 1000-2000.

[0137] The length of the inlets 210 corresponds to a thickness of the first layer 202. The thickness of the first layer 202 may affect a stability of the collecting device 200, together with a thickness of the second layer 220 and a gap between the first 202 and second layers 220, such that the thickness of the first layer 202 should not be too small and, hence the length of the inlets 210 should not be too small. However, a liquid reagent filled into the particle collection chamber 240 may also be filled into the inlets 210 and the outlets 230, such that the length of the inlets 210 affect an overall liquid volume filling the particle collection chamber 240. Thus, the length of the inlets 210 should not be too large.

[0138] Therefore, the length of the inlets 210 of the collecting device 200 may be in a range of 20-500 μm. Preferably, the length of the inlets 210 is in a range of 50-300 μm.

[0139] A small gap between the first layer 202 and the second layer 220 is beneficial for providing a high collection efficiency. A small gap also facilitates having a small volume of the particle collection chamber 240. However, a small gap may also imply that the pressure drop experienced by the flow of air 104 passing through the collecting device 200 is relatively high.

[0140] Thus, in order to balance the collection efficiency and the volume of the particle collection chamber 240 with the pressure drop experienced by the flow of air 104, the gap may be in the range of 10-150 μm. Preferably, the gap may be in the range of 20-100 μm.

[0141] Further, the gap may be related to the size of the inlets 210 in order to avoid large pressure drops when the flow of air 104 passes through the collecting device 200. A size ratio between the gap and a diameter of a circular inlet 210 may be in a range of 0.1-0.6.

[0142] A projection of the inlets 210 along the respective center axes of the inlets 210 onto the first surface 222 of the second layer 220 may be arranged not to intersect with the first ends 232 of the outlets 230 in the second layer 220. This implies that the flow of air 104 following an extension of the inlets 210 will impinge on a part of the first surface 222 of the second layer 220 allowing particles to be captured at the first surface 222. However, it should be realized that even if there is an overlap between the projection of the inlets 210 and the outlets 230, the flow of air 104 will at least slightly change direction by the center axes of the inlets 210 and outlets 230 not being aligned. Therefore, collection of particles may be provided in the particle collection chamber 240 even if there is an overlap between the projection of the inlets 210 and the outlets 230.

[0143] However, for ensuring that a high collection efficiency is provided, the projection of the inlets 210 and the outlets 230 may be configured not to overlap. In order to cause a larger change of direction of the flow of air 104, there may be a lateral separation of at least 20 μm between an edge of the projection of an inlet 210 and an edge of the closest neighbor outlet.

[0144] The size and shape of the outlets 230 may be set in relation to the size and shape of the inlets 210 such that the outlets 230 may be symmetrically arranged in relation to the inlets 210 and that the flow of air 104 passes through inlets 210 and outlets 230 of similar dimensions. This may facilitate that a low pressure drop is experienced by the flow of air 104 when passing the collecting device 200. Further, the size and shape of the outlets 230 may be set in relation to the size and shape of the inlets 210 such that the inlets 210 and the outlets 230 may be staggered.

[0145] Using the smallest dimension of the cross-section of the outlets 230 in the range of 20-400 μm and in particular in the range of 100-300 μm facilitates that the pressure drop in the flow of air passing the collecting device will be lower than 3 kPa, even lower than 1.5 kPa, at a flow rate of 0.5 liters per second.

[0146] The outlets 230 may be slightly larger than the inlets 210 since the outlets 230 are not directly involved in the particle collection.

[0147] The cross-section of the outlets 230 may be circular. This may be suitable for manufacturing of the collecting device 200. Also, it may ensure that a symmetric behavior of the flow of air 104 flowing through the outlets 230 is provided around the central axis of the outlet 230. For a circular cross-section, the smallest dimension of the outlet 230 is the diameter of the outlet 230. However, it should be realized that other shapes of the cross-section of the outlets 230 are conceivable. For instance, the outlets 230 may be rectangular and may even be in the form of elongate rectangular slits.

[0148] The number of outlets 230 used may fit a total flow rate provided into the collecting device 200 from the inlets 210 and an associated pressure drop experienced by the flow of air 104. The outlets 230 may be arranged such that the flow of air 104 entering the particle collection chamber 240 through an inlet 210 will be able to escape the particle collection chamber 240 through an outlet 230 without necessarily passing another adjacent inlet 210. This may ensure that behavior of the flow of air 104 is not changed in the particle collection chamber 240 so that no large pressure drop occurs in the particle collection chamber 240.

[0149] With large outlets 230, each outlet 230 supports a relatively large flow rate, whereas small outlets 230 support a relatively small flow rate. Thus, the number of outlets 230 may need to be larger for smaller outlets 230.

[0150] The number of outlets 230 may be similar to the number of inlets 210, although the number of outlets 230 need not be exactly the same as the number of inlets 210. Since the outlets 230 may be slightly larger than the inlets 210, as discussed above, the number of outlets 230 may be slightly smaller than the number of inlets 210.

[0151] However, the size of the outlets 230 is preferably small, such that the number of outlets 230 may need to be quite large, such as more than 100, or more than 500, such as in a range of 1000-2000.

[0152] The length of the outlets 230 corresponds to a thickness of the second layer 220. The thickness of the second layer 220 may affect a stability of the collecting device 200, together with a thickness of the first layer 202 and a gap between the first 202 and second layers 220. In particular, as the second layer 220 may function as a substrate of the collecting device 200, the thickness of the second layer 220 should not be too small. Also, in order to ensure an overall stability of the collecting device 200, a combined thickness of the second layer 220, the gap between the first 202 and second layers 220, and the first layer 202, may be at least 450 μm. However, a liquid reagent filled into the particle collection chamber 240 may also be filled into the inlets 210 and the outlets 230, such that the length of the outlets 230 affect an overall liquid volume filling the particle collection chamber 240. Thus, the length of the outlets 230 should not be too large.

[0153] Therefore, the length of the outlets 230 of the collecting device 200 may be in a range of 20-500 μm. Preferably, the length of the outlets 230 is in a range of 100-300 μm.

[0154] Referring now to FIG. 4, an arrangement of the inlets 210 and the outlets 230 according to an embodiment will be discussed. FIG. 4 illustrates the arrangement of a projection of the shape and size of the inlets 210 at the second end 214 onto the first surface 222 of the second layer 220. FIG. 4 further illustrates the first ends 232 of the outlets 230 such that the relative arrangement of the inlets 210 and the outlets 230 is shown.

[0155] Six inlets 210 are arranged around each outlet 230 with an even distribution of the six inlets 210 around a circumference of the outlet 230. Thus, the inlets 210 form a hexagonal arrangement surrounding the outlet 230. Further, each inlet 210 is arranged between three outlets 230 with the three outlets 230 separated by an equal lateral separation in relation to the inlet 210.

[0156] The lateral separation between an edge of the projection of the inlet 210 and edges of the three outlets 230 closest to the inlet 210 may be smaller than a lateral separation between adjacent inlets 210.

[0157] The arrangement of the inlets 210 and outlets 230 as shown in FIG. 4 provides that the flow of air 104 entering the particle collection chamber 240 through an inlet 210 will be able to escape the particle collection chamber 240 through an outlet 230 without necessarily passing another adjacent inlet 210. This may ensure that behavior of the flow of air 104 is not changed in the particle collection chamber 240 so that no large pressure drop occurs in the particle collection chamber 240.

[0158] The arrangement of the inlets 210 and the outlets 230 further provides an efficient use of a footprint (area of the first layer 202 and/or the second layer 220) of the collecting device 200 while arranging the inlets 210 and the outlets 230 with no overlap.

[0159] However, it should be realized that the inlets 210 and the outlets 230 may be arranged in many other relations to each other. For instance, the projection of the inlets 210 and the outlets 230 may form a plurality of rows, wherein every other row is formed by inlets 210 and every other row is formed by outlets 230.

[0160] Referring now to FIG. 5, an arrangement of the inlets 210 and the outlets 230 according to another embodiment will be discussed. FIG. 5 also illustrates the arrangement of a projection of the shape and size of the inlets 210 at the second end 214 onto the first surface 222 of the second layer 220. FIG. 5 further illustrates the first ends 232 of the outlets 230 such that the relative arrangement of the inlets 210 and the outlets 230 is shown.

[0161] The arrangement of the inlets 210 and outlets 230 as shown in FIG. 5 also provides that the flow of air 104 entering the particle collection chamber 240 through an inlet 210 will be able to escape the particle collection chamber 240 through an outlet 230 without necessarily passing another adjacent inlet 210. This may ensure that behavior of the flow of air 104 is not changed in the particle collection chamber 240 so that no large pressure drop occurs in the particle collection chamber 240.

[0162] The collection efficiency of the particles is mainly determined by a smallest dimension of the cross-section of the inlet 210, such that a substantially larger dimension of the cross-section in a direction perpendicular to a direction of the smallest dimension could be used. Thus, as shown in FIG. 5, the inlets 210 may be designed as rectangular slits having a very large length and a small width. The width may be in the range of 20-300 μm, such as in the range of 100-200 μm in order to provide at least a desired efficiency of collection of particles and an acceptable pressure drop to be experienced by the flow of air 104 when passing through collecting device 200. The length of the rectangular slits may be in an order of millimeters, such as several or even tens of millimeters.

[0163] The use of rectangular slits may allow for an efficient arrangement of the inlets 210 and outlets 230 such that a small footprint of the collecting device 200 may be achieved.

[0164] Referring now to FIGS. 6-8, cross-sections of embodiments of the collecting device 200 are disclosed illustrating different sizes of parts of the collecting device 200. In each of the embodiments of FIGS. 6-8, circular cross-sections of the inlets 210 and outlets 230 are used. Also, the inlets 210 and outlets 230 are arranged in a hexagonal arrangement in relation to each other.

[0165] In the embodiment illustrated in FIG. 6, each inlet 210 has a diameter of 150 μm and a length of 100 μm. The collecting device 200 has 1600 inlets 210. Each outlet 230 has a diameter of 150 μm and a length of 320 μm. Further, there is a lateral separation of 20 μm between an edge of the projection of the inlet 210 and an edge of the adjacent outlet 230. There is a vertical gap between the first layer 202 and the second layer 220 of 30 μm.

[0166] Further, a width of the particle capturing chamber 240 is 10.6 mm and a volume of the particle capturing chamber 240 is 15.8 μl.

[0167] Using the collecting device 200 as described in relation to FIG. 6, the flow of air 104 experiences a pressure drop of 1.3 kPa at a flow rate of 0.5 liters per second. Further, the collecting device 200 is configured to provide a collection efficiency of 50% for particles having a diameter of 352 nm. In the embodiment illustrated in FIG. 7, each inlet 210 has a diameter of 125 μm and a length of 100 μm. The collecting device 200 has 1561 inlets 210. Each outlet 230 has a diameter of 125 μm and a length of 300 μm. Further, there is a lateral separation of 20 μm between an edge of the projection of the inlet 210 and an edge of the adjacent outlet 230. There is a vertical gap between the first layer 202 and the second layer 220 of 50 μm.

[0168] Further, a width of the particle capturing chamber 240 is 8.1 mm and a volume of the particle capturing chamber 240 is 11.9 μl.

[0169] Using the collecting device 200 as described in relation to FIG. 7, the flow of air 104 experiences a pressure drop of 1.9 kPa at a flow rate of 0.5 liters per second. Further, the collecting device 200 is configured to provide a collection efficiency of 50% for particles having a diameter of 300 nm.

[0170] In the embodiment illustrated in FIG. 8, each inlet 210 has a diameter of 200 μm and a length of 100 μm. The collecting device 200 has 1015 inlets 210. Each outlet 230 has a diameter of 200 μm and a length of 290 μm. Further, is a lateral separation of 20 μm between an edge of the projection of the inlet 210 and an edge of the adjacent outlet 230. There is a vertical gap between the first layer 202 and the second layer 220 of 60 μm.

[0171] Further, a width of the particle capturing chamber 240 is 9.9 mm and a volume of the particle capturing chamber 240 is 20.2 μl.

[0172] Using the collecting device 200 as described in relation to FIG. 8, the flow of air 104 experiences a pressure drop of 0.7 kPa at a flow rate of 0.5 liters per second. Further, the collecting device 200 is configured to provide a collection efficiency of 50% for particles having a diameter of 500 nm.

[0173] Thus, it may be seen from the embodiments discussed in FIGS. 6-8 that a lower pressure drop experienced by the flow of air 104 passing the collecting device may be associated with a larger volume of the particle capturing chamber 240 and a larger size of the particles being captured with a collection efficiency of 50%.

[0174] Referring now to FIG. 9, a method for collection of airborne particles exhaled by a human being will be described.

[0175] The method comprises receiving 302 a flow of air 104 from a human being onto a plurality of inlets 210 of a collecting device 200. The method further comprises passing 304 the flow of air 104 through the inlets 210 into a particle collection chamber 240.

[0176] The plurality of inlets 210 may extend through at least a first layer 202. The flow of air 104 may thus be received on a surface forming an interface between the collecting device 200 and an external environment outside the collecting device 200, e.g. an internal space in a sampling compartment of a sample collector 100. The flow of air 104 is passed by the plurality of inlets 210 from the external environment outside the collecting device 200 into the particle capturing chamber 240. The particle capturing chamber 240 may be defined between the first layer 202 and a second layer 220 of the collecting device 200 spaced apart from the first layer 202.

[0177] The method further comprises capturing 306 airborne particles in the flow of air 104 entering the particle collection chamber 240 by impaction of airborne particles on a first surface 222 of the second layer 220. The method further comprises passing 308 the flow of air 104 out of the particle collection chamber 240 through outlets 230 extending through at least the second layer 220 of the collecting device 200 to an external environment outside the collecting device 200.

[0178] The inlets 210 and the outlets 230 are staggered such that the center axes of the inlets 210 are displaced from the center axes of the outlets 230 and the center axes of the inlets 210 and the outlets 230 are not aligned. Thus, ends 214 of the inlets 210 are configured to face the first surface 222 of the second layer 220, such that particles are captured at the first surface 222 between the outlets 230. The method thus causes the flow of air 104 to be forced to change direction, such that momentum of particles having a certain size will cause the particles not to follow the flow of air 104 in its change of direction and instead the particles will be captured on the first surface 222.

[0179] The method passes the flow of air 104 through a collecting device 200 such that the flow of air 104 experiences a pressure drop when passing the collecting device 200, wherein the pressure drop is such that if the flow rate of the flow of air is 0.5 liters per second, the pressure drop will be lower than 3 kPa.

[0180] In the above the inventive concept has mainly been described with reference to a limited number of examples. However, as is readily appreciated by a person skilled in the art, other examples than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.