Optoelectronic aerosol sensor

Abstract

An optoelectronic aerosol sensor uses a combination of light-scattering and electrical classification to detect and measure properties of aerosol particles, including particle diameter, particle number concentration, particle mass concentration (including PM1.0, PM2.5, PM4.0, and PM10), and particle compositional type (e.g., smoke, dust, biological particles). The sensor is compact and can provide real-time aerosol characterization in a variety of settings by making sensitive measurements of particles in a sampled airflow using laser diode placement, photo-current detection, and electric field displacement. Particles in an airflow can be detected in a size range of 100 nm to 30 μm, particle concentrations can be determined in a range of 0 to 100,000 particles per cm3, and particle mass concentration can be determined in a range of 0.01 μg / m3 to 10 mg / m3.

Description

OPTOELECTRONIC AEROSOL SENSORRELATED APPLICATION DATA

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application Serial No. 63 / 595,816, filed November 3, 2023, and titled “Optoelectronic Aerosol Sensor”, which is incorporated by reference herein in its entirety.FIELD OF THE DISCLOSURE

[0002] The present disclosure generally relates to the field of aerosol sensors. In particular, the present disclosure is directed to an optoelectronic real-time aerosol sensor.BACKGROUND

[0003] Quality of outdoor air is regulated by EP A, due to health effects from air pollution. Indoor air is not regulated, but of importance in spaces such as classrooms, office spaces, etc., from a public health perspective and also in manufacturing facilities from a worker health and product quality perspective. Monitoring tools would ideally be able to detect and measure the quantity of airborne particles (e.g., airborne particulates with masses smaller than 2.5 pm (PM2.5)), sizes of particles, and composition of particles. Currently such measurements are only possible with a suite of research-grade instruments that are bulky, expensive, and difficult to operate.

[0004] There is a need for low-cost, compact, easy-to-use sensors for widespread deployment, including for integration with ventilation systems.SUMMARY OF THE DISCLOSURE

[0005] An optoelectronic aerosol sensor includes a housing having an inlet port and an outlet port, an air circulation device configured to draw air into the housing through the inlet port, through an airflow channel, and out the outlet port, a first laser for generating a first beam at a first wavelength, the first laser positioned to send the first beam through a light scattering region in the airflow channel, a second laser for generating a second beam at a second wavelength, the second laser positioned to send the second beam through the light scattering region, a plurality of photosensors beneath the airflow channel in the light scattering region positioned to detect light from the first beam and the second beam scattered off of particles, an electric charge region in the airflow channel downstream from the light scattering region including a pair of charge plates on oppositesides of the airflow channel, a third laser for generating a third beam, the third laser positioned to send the third beam through a second light scattering region downstream of the pair of electric charge plates, and a second plurality of photosensors positioned to detect beneath the airflow channel in the second light scattering region positioned to detect light from the third beam scattered off of particles.

[0006] Additionally or alternatively, the first beam passes through the airflow channel at a focus spot and the second beam passes through the airflow channel at the focus spot orthogonal to a direction of the first beam.

[0007] Additionally or alternatively, the plurality of photosensors includes a first photosensor beneath the focus spot positioned to detect orthogonal scattering, a second photosensor downstream from the first photosensor positioned to detect back scattering, and a third photosensor upstream from the first photosensor positioned to detect forward scattering.

[0008] Additionally or alternatively, the second plurality of photosensors includes a fourth photosensor beneath a first side of the airflow channel positioned to detect scattering from particles deflected in a first direction in the electric charge region and a fifth photosensor beneath a second side of the airflow channel positioned to detect scattering from particles deflected in a second direction that is opposite the first direction in the electric charge region.

[0009] Additionally or alternatively, a barrier at least partially encompassing and extending up from the fourth and fifth photosensors is included.

[0010] Additionally or alternatively, the barrier extends 1 mm above the fourth and fifth photosensors.

[0011] Additionally or alternatively, the first laser is configured to direct the first beam at an angle of between about 40 degrees and about 50 degrees with respect to a direction of flow of the airflow channel at a point of intersection with the airflow channel.

[0012] Additionally or alternatively, the second laser is configured to direct the second beam at an angle of between about 40 degrees and about 50 degrees with respect to the direction of flow of the airflow channel at a point of intersection with the airflow channel.

[0013] Additionally or alternatively, the focus spot has a diameter of less than 50 micrometers.

[0014] Additionally or alternatively, the first laser has a wavelength of between about 635 nm and 650 nm, the second laser has a wavelength of about 450 nm, and the third laser has a wavelength of between about 375 nm and 380 nm.

[0015] Additionally or alternatively, a voltage between the pair of electric charge plates are configured to produce an electric field of 1000 V / cm to 30,000 V / cm.

[0016] Additionally or alternatively, the first, second, and third photosensors are photodiodes.

[0017] Additionally or alternatively, the fourth and fifth photosensors are photodiodes.

[0018] Additionally or alternatively, a pair of UV lasers are positioned to send beams to the focus spot and a spectrometer positioned beneath the focus spot.

[0019] Additionally or alternatively, the plurality of photosensors includes a first photodiode beneath and downstream from the focus spot positioned to detect back scattering and a second photodiode upstream of the first photodiode positioned to detect forward scattering, wherein the spectrometer is between the first photodiode and the second photodiode.

[0020] Additionally or alternatively, one or more of the first, second, and third photosensors is a spectrometer.

[0021] Additionally or alternatively, a flow sensor, a temperature sensor, and a relative humidity sensor are configured to monitor the airflow conditions.

[0022] Additionally or alternatively, the first laser is configured to direct the first beam at an angle of between about 40 degrees and about 50 degrees with respect to a direction of flow of the airflow channel at a point of intersection with the airflow channel.

[0023] Additionally or alternatively, the second laser is configured to direct the second beam at an angle of between about 40 degrees and about 50 degrees with respect to the direction of flow of the airflow channel at a point of intersection with the airflow channel.

[0024] An optoelectronic aerosol sensor includes a housing having an inlet port and an outlet port, an air circulation device configured to draw air into the housing through the inlet port, through an airflow channel, and out the outlet port, a first laser for generating a first beam at a first wavelength, the first laser configured to send the first beam through a focus spot in the airflow channel, wherein the focus spot has a diameter of less than 50 micrometers, a second laser for generating a second beam at a second wavelength, the second laser configured to send the second beam through the focus spot, a first photodiode positioned beneath to the focus spot and configured to detect light scattered from particles in the focused spot, a second photodiode positioned upstream from the focus spot and configured to detect light scattered from particles in the focus spot, a third photodiode positioned downstream from the focused spot and configured to detect light scattered from particles in the focus spot, an electric charge region downstream from the focus spot including a pair of charge plates on opposite sides of the airflow channel, a third laser for generating a third beam configured to send the third beam through the airflow channel downstream from the pair of charge plates, a fourth photodiode positioned beneath a first side of the airflow channel downstream from the pair of charge plates configured to detect light scattered from particles deflected toward the first side of the airflow channel, and a fifth photodiode positioned beneath a second side of the airflow channel downstream from the pair of charge plates configured to detect light scattered from particles deflected toward the second side of the airflow channel.

[0025] Additionally or alternatively, the sensor has a volume of about 400 cm3.

[0026] A method for detecting and classifying aerosol particles is disclosed that includes drawing air into a sensor housing and through an airflow channel within the sensor housing, directing a first laser beam having a first wavelength at a focus spot in a light scattering region of the airflow channel, wherein the first laser beam is at an angle of about 45 degrees with respect to a direction of flow of the airflow channel, directing, alternatingly with respect to the first laser beam, a second laser beam having a second wavelength, at the focus spot, wherein the second laser beam is at an angle of about 45 degrees with respect to a direction of flow of the airflow channel, detecting light scattered from particles interacting with the first laser beam and the second laser beam at a plurality of photosensors positioned beneath the airflow channel in the light scattering region, applying an electric field across the airflow channel downstream from the light scattering region, directing a third laser beam through the airflow channel downstream from the electric field, anddetecting light scattered from particles interacting with the third laser beam at a first photosensor positioned beneath and on a first side of the airflow channel downstream from the electric field and from particles interacting with the third laser beam at a second photosensor positioned beneath and on a second side of the airflow channel downstream from the electric field.

[0027] Additionally or alternatively, the first laser beam and the second laser beam have paths that are about 90 degrees from each other.

[0028] Additionally or alternatively, each pulse of the first laser beam and the second laser beam have a duration of about 1 ms and are repeated altematingly.

[0029] Additionally or alternatively, the plurality of photosensors includes a first photosensor located beneath the focus spot, a second photosensor located downstream from the first photosensor, and a third photosensor located upstream from the first photosensor.

[0030] Additionally or alternatively, the method includes correlating signals received at the plurality of photosensors with periods when the first laser beam and the second laser beam, respectively, interacted with particles in the airflow channel in the light scattering region.

[0031] Additionally or alternatively, the electric field is 1000 V / cm to 30,000 V / cm.

[0032] Additionally or alternatively, the first laser beam has a wavelength of between about 635 nm and 650 nm, the second laser beam has a wavelength of about 450 nm, and the third laser beam has a wavelength of between about 375 nm and 380 nm.

[0033] Additionally or alternatively, the focus spot has a diameter of less than 50 micrometers.

[0034] Additionally or alternatively, the method includes determining a flow rate of air through the airflow channel.BRIEF DESCRIPTION OF THE DRAWINGS

[0035] For the purpose of illustrating the disclosed embodiments, the drawings show aspects thereof. It is to be understood, however, that the teachings of the present disclosure are not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:FIG. 1A is a front perspective view of an optoelectronic aerosol sensor in accordance with an embodiment of the present disclosure;FIG. IB is a side perspective view of the optoelectronic aerosol sensor of FIG. 1A;FIG. 2 is a top perspective view of the optoelectronic aerosol sensor with the cover removed showing the airflow channel;FIG. 3A is a top view of another optoelectronic aerosol sensor with the cover removed showing the airflow channel;FIG. 3B is a top perspective view of the optoelectronic aerosol sensor with the cover removed showing the airflow channel including an arrow overlay showing the path of the air;FIG. 3C a detailed view of the airflow channel portion of FIG. 3B including dotted lines depicting paths of laser beams;FIG. 4 is a top view another optoelectronic aerosol sensor with the cover removed that includes additional lasers and a spectrometer;FIG. 5 is a schematic diagram of components, light paths, and airflow in accordance with an embodiment of the present disclosure; andFIG. 6 is a graph of the ratio of forward to back scattering versus particle diameter for different wavelengths of light.DETAILED DESCRIPTION

[0036] An optoelectronic aerosol sensor uses a combination of light-scattering and electrical classification to detect and measure properties of aerosol particles, including particle number concentration, particle mass concentration (including PM1.0, PM2.5, PM4.0, and PM10), andparticle compositional type (e.g., smoke, dust, biological particles, etc.). The sensor is compact and can provide real-time aerosol characterization in a variety of settings by making sensitive measurements of particles in a sampled airflow using laser diode placement, photo-current detection, and electric field displacement. Particles in the sampled airflow can be detected and sized over a diameter range of 100 nm to 30 pm, particle concentrations can be determined in a range of 0 to 100,000 particles per cm3, and particle mass concentration can be determined in a range of 0.01 pg / m3to 10 mg / m3.

[0037] The sensor employs multiple lasers and multiple photodetectors, such as photodiodes, complementary metal-oxide semiconductors (CMOS), and spectrometers, that in conjunction allow the characterization of particle physical properties and optical signatures that are representative of particle composition. The sensor can accurately measure PM1, PM2.5, and PM10 particles, independent of aerosol type through the analysis of signals obtained from multiple lasers and multiple photodetectors positioned at various points with respect to the airflow path and the laser paths, which also allows for the measurement of size distribution of particles from 100 nm to 30 pm. In addition, the sensor classifies particles by type using the multi-dimensional optical signals and electrical mobility measurements.

[0038] At a high level, the sensor includes an airflow path having an air intake port and an air exit for sampling air at selected times, intervals, or continuously. Within the sensor device, the airflow passes through multiple laser beams. Preferably, the lasers beams are of different wavelengths (e.g., 650 / 635nm, 450 nm, 375 / 380 nm, 250 to 280 nm) and are configured to be focused to a very small spot size (~ 20 pm to 50 pm) very close to the module (e.g., focal length around 10 mm to 20 mm) in the airflow path, which allows less powerful lasers to be used while still generating sufficient scattering off of sampled particles. The lasers can be configured such that only one laser interacts with particles in the airflow at the focus point at any given time.

[0039] Multiple photodetectors, which in a preferred embodiment may be photodiodes, are positioned at different angles with respect to the focused laser point. Preferably one photodetector is orthogonal to the focused laser point with a second located at an angle upstream from the focused laser point (capturing forward scattering signal) and a third located at an angle downstream from the focused laser point (capturing backward scattering signal).

[0040] Tn this way, a set of scattering signatures (pulse width and height from photodetectors at different scattering angles, i.e., as detected at the differently located photodetectors) are collected for each particle interacting with each of the laser diodes and these scattering signatures are representative of the size, shape, and composition of the particle in the beam. While the scattered light will almost always be more prevalent in the forward angle, however, as particle size increases, the backward scattering angle will be a better indicator of size as its less likely to be saturated. Each particle will provide three signals in the three photodetectors. Analysis of the signal properties (e.g., pulse heights, pulse widths, and pulse shape) at the three photodetectors positioned along the airflow path can provide particle size distribution in addition to its shape and composition.

[0041] The width and intensity of light of the laser beams will not be completely uniform, particularly as the distance from the focused point increases. Because of this non-uniform light intensity, particle scattering responses will vary depending on where particles are with respect to the light beams when they interact with the light. The effects of light scattered by these interactions will be reduced by ensuring that the photodetectors only receive scattered light from a small viewing volume and by using machine learning to eliminate signals that were detected from particles that were not in the laser spot when the light interacted with the particles.

[0042] In a preferred embodiment, the lasers are positioned such that beams are directed toward the airflow channel at an angle, for example, between 40 degrees and 50 degrees, and preferably about 45 degrees. This allows the photodiodes to be placed in the flow channel such that forward and backward scattering is captured while keeping the area around the photodiodes continuously flushed so that there accumulation of particles is avoided.

[0043] After the particles pass through the focused laser point, the airflow moves into an electric field region in which plates on either side of the airflow are used to generate an electric field across the airflow path. The electrodes may be straight plates, but may also include other shapes to increase the length of flow in the applied electric field while keeping the overall size of the unit small, for example, the path could be more tortuous. Neutral particles will be unaffected by electric field while charged particles will move towards the oppositely charged plates. The spatial nonuniformity of particles at the end of the electric field region will be captured by a laser beam passing normal to the flow. Light scattered off of passing particles is detected by at least a pair ofphotodetectors positioned along the beam with one photodetector positioned to detect particles that moved toward the positively charged plate and one photodetector positioned to detect particles that moved toward the negatively charged plate. Based on the degree of deflection and the intensity of light detected, the average particle charge is determined. The average particle charge and sign of charge is an additional indicator of particle composition. For example, freshly formed smoke particles will be more highly charged than older smoke particles from outdoor environment. The photodetector measurements are made using a sensitive trans-impendence amplifier circuit to detect very small amounts of scattered light. The signals may be preferably recorded at 1 MHz for increased resolution of widths and heights of detected signals.

[0044] Analysis of signals detected at this stage for size measurements and compositional characterization may be made with a fast on-board micro-controller, so as to enable real-time classification and characterization of particles. For alternating pulses of different lasers and photodetectors detecting scattered light, the positions of the photodetectors with respect to the focus point is correlated with the type of scattering and the timing of detections is correlated to the laser (and hence wavelength) that would have sent the light that was detected at that time. Under higher concentrations (particle concentrations > 100 per cm3), characterization of particles may be made based on 1 second of sample flow (which may be on the order of about 10 LPM) through the detection system. At lower concentrations, comparably accurate characterizations may require 3 to 10 seconds of collected data from particles passing in the airflow.

[0045] Alternatively, all the lasers can be configured to emit light to interact with the particles simultaneously. When all lasers are simultaneously directing light toward focus point, the scattered light from particles in the airflow may be detected by a spectrometer positioned near the focus point that provides wavelength dependent measurements. This allows the same information to be determined from the data, while alternating lasers and firing them one at a time allows for the use of broad response sensors that are smaller and cheaper.

[0046] In addition, for certain bioaerosol measurements, UV lasers (e.g., 220 nm to 380 nm) are used to excite the particles and a spectrometer to measure scattered light as a function of wavelength. These lasers may be in addition to the lasers discussed above. The resulting laser inducedfluorescence is detected by the spectrometer and can be used to determine characteristics associated with biological particles.

[0047] Turning to the figures, FIGS. 1 A and IB are perspective views of an optical aerosol sensor 100 for detecting and measuring aerosol particles that includes a housing 104, an air intake port 108 and an air exit 112, as well as a display 102, a power connector 106, and a data access port 110. Sensor 100 may be relatively compact (e.g., a sensor may have a volume of 400 cm3) and therefore is able to be used in many applications and settings, including in residences, office spaces, vehicles, and on individuals.

[0048] FIGS. 2-3 C illustrate an exemplary flow path for sampled air and sensor components used to analyze particles in the air sample. FIG. 2 is a top perspective view of optoelectronic aerosol sensor 100 with the top removed to show an airflow path 116 through sensor 100. FIG. 3 A is a top view of optoelectronic aerosol sensor 100 with the cover removed showing the airflow channel 116. FIG. 3B is a top perspective view of the optoelectronic aerosol sensor 100 with the cover removed showing the airflow channel 116 including an arrow 103 overlay schematically depicting the path of the air. FIG. 3C is a detailed view of the airflow channel portion of FIG. 3B including dotted lines depicting paths of laser beams 101 (e.g., lOla-lOlc).

[0049] Sensor 100 will include a fan or similar device to control airflow through airflow path 116 and an additional fan to cool components, as well as circuit boards and a processor for controlling the components of sensor 100 and performing analysis of data collected by sensors along airflow path 116. Components include the sample air intake 108 and air exit 112, a plurality of photodiodes 124 (e.g., 124a-124e), a plurality of lasers 128 (e.g., 128a-128c), and charge plates 134 (e.g., 134a- 134b) in an electric field region. An airflow separator or photosensor barriers 136 (as can best be seen in FIG. 3C) may also be included to limit light from particles from being detected by certain sensors (as described further below). In addition, a flow sensor 117 and temperature and relative humidity sensor 119 may be included for monitoring sampled air parameters.

[0050] In operation, air is brought in through air intake 108 and flows through the airflow channel 116 and reaches a laser focus point 144 (FIG. 3C), where particles in the airflow may interact with the beams from lasers 128a and 128b, which are preferably passed through focus point 144 one at a time for selected durations such that only light of one wavelength interacts with theparticles at any given time. Further, the laser beams are at 90 degrees from each other in preferred embodiments. Light scattered during these interactions may be detected by any of photodiodes 124a- 124c positioned near laser focus point 144, preferably along airflow path 116. For example, photodiode 124b may be about 1.5 mm below the laser beam. Scattered light detected at upstream photodiode 124c is forward scattering signal. Scattered light detected at downstream photodiode 124a is backward scattering signal. Scattered light detected at photodiode 124b is scattering signal directly beneath focus point 144. Light that passes through the airflow is absorbed at laser dumps 135 (e.g., 135a-135c).

[0051] Because scattering signal characteristics depend on wavelengths, using light sources of different wavelengths can double the number of scattering signatures available for particle characterization. In an embodiment, having the wavelengths of one laser be in the UV range can allow for detection of wavelength dependent fluorescence of particles, which can enhance the detection and characterization of biological particles.

[0052] After passing through the light scattering region, particles in the airflow continue along the airflow path 116 and move into an electric field region, where neutral particles remain on a similar trajectory through the airflow path and charged particles, depending on the magnitude of charge and their mass, are deflected toward one or the other of oppositely charged charge plates 134, which create an electric field of 1000 V / cm to 30,000 V / cm that deflects charged particles toward one or the other of the plates. The particles then pass over another set of photosensors, such as photodiodes 124d and 124e, which are positioned on opposite sides of the airflow channel 116. Laser 128c provides a beam across the airflow path 116 over the photosensors, which may interact with particles in the airflow. The laser light that interacts with such particles is scattered, and a portion of the scattered light is detected at either photodiode 124d or 124e, depending on which side of the airflow the particle is on, which as noted is determined by the mass and charge of the particle. Sidewalls or barriers 136 may be used to extend upward around and between photosensors 124d and 124e in order to limit the amount of light detected from particles that are farther away from a given photosensor (i.e., light from particles that are on the opposite side of the airflow from the photosensor. In a preferred embodiment, barriers 136 may extend about 1 mm above the photosensors. From these signals, an average particle charge can be determined.

[0053] Tn an alternative embodiment, a separator extends across the middle of the airflow so that negatively charged particles tend to pass on one side of the separator and positively charged particles tend to pass on the other side of the separator. A hole in the separator allows for passage of the laser beam, which may interact with particles in the airflow. The laser light that interacts with such particles is scattered, and a portion of the scattered light is detected at either photodiode 124d or 124e, depending on which side of the separator the particle passes.

[0054] With the information obtained signals detected from the laser at a first wavelength, the laser at a second wavelength, the position of the scattered light from each of those lasers as determined by the photodiodes positioned at the focus point, upstream from the focus point, and downstream from the focus point, together with signals from the photodiodes downstream of the electric field hat provide particle charge data, sampled particles can be categorized and characterized by type, size, and concentration. This can be done essentially in real time, and data can be sent to users or databases for monitoring, and alerts can be sent based on selected thresholds (e.g., concentrations of certain types of particles) or other parameters.

[0055] In another embodiment, an optical aerosol sensor 200 for detecting and characterizing aerosol particles is shown in FIG. 4 (with a top cover removed) that includes a housing 204, an air intake port and an air exit. Sensor 200 may be relatively compact (e.g., a sensor may have a volume of 400 cm3) and therefore is able to be used in many applications and settings, including in residences, office spaces, vehicles, and on individuals. Sensor 200 includes the components described above for sensor 100, including an airflow channel, an electric charge region, and a light scattering region, except that the light scattering region includes additional lasers, UV lasers 229 (e.g., 229a, 229b) that are directed to a focus spot 250 (illustrated by a circle in FIG. 5) along with lasers 228 (e.g., 228a, 228b), and may include a spectrometer 231 in place of one of the photodiodes 224 (e.g., 224a and 224c are on either side of spectrometer 231).

[0056] In this way, as depicted in FIG. 5, as aerosol particles travel through airflow channel 216 (shown as a block arrow 213) in the light scattering region, lasers 228 direct beams at focus point 250 as described above and photodiodes 229a and 229c detect light back and forward scattered, respectively, off of the particles. Beams from UV lasers 229 are also directed at focus spot 250, causing UV induced fluorescence in particles, particularly biological particles, in the airflow.Fluorescence from such particles may be detected by spectrometer 231, and based on the detected wavelengths, characteristics of biological particles can be determined. This information, in combination with particle size information derived from the detection of scattered light at photodiodes 224, can be used to further identify such particles.

[0057] FIG. 6 is a graph of the ratio of forward to back scattering versus particle diameter shown for two different wavelengths of light, from which it can be seen that the ratio depends on both particle size and the wavelength of the scattered light.

[0058] The term “about” when used with a corresponding numeric value refers to ±20% of the numeric value, typically ±10% of the numeric value, often ±5% of the numeric value, and most often ±2% of the numeric value. In some embodiments, the term “about” can be taken as exactly indicating the actual numerical value.

[0059] Various modifications and additions can be made without departing from the spirit and scope of this disclosure. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments, what has been described herein is merely illustrative of the application of the principles of the present disclosure. Additionally, although particular methods herein may be illustrated and / or described as being performed in a specific order, the ordering is highly variable within ordinary skill to achieve aspects of the present disclosure. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this disclosure.

[0060] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present disclosure.

Claims

What is claimed is:

1. An optoelectronic aerosol sensor comprising: a housing having an inlet port and an outlet port; an air circulation device configured to draw air into the housing through the inlet port, through an airflow channel, and out the outlet port; a first laser for generating a first beam at a first wavelength, the first laser positioned to send the first beam through a light scattering region in the airflow channel; a second laser for generating a second beam at a second wavelength, the second laser positioned to send the second beam through the light scattering region; a plurality of photosensors beneath the airflow channel in the light scattering region positioned to detect light from the first beam and the second beam scattered off of particles; an electric charge region in the airflow channel downstream from the light scattering region including a pair of charge plates on opposite sides of the airflow channel; a third laser for generating a third beam, the third laser positioned to send the third beam through a second light scattering region downstream of the pair of electric charge plates; and a second plurality of photosensors positioned to detect beneath the airflow channel in the second light scattering region positioned to detect light from the third beam scattered off of particles.

2. The optoelectronic aerosol sensor of claim 1, wherein the first beam passes through the airflow channel at a focus spot and the second beam passes through the airflow channel at the focus spot orthogonal to a direction of the first beam.

3. The optoelectronic aerosol sensor of claim 2, wherein the plurality of photosensors includes a first photosensor beneath the focus spot positioned to detect orthogonal scattering, a second photosensor downstream from the first photosensor positioned to detect back scattering, and a third photosensor upstream from the first photosensor positioned to detect forward scattering.

4. The optoelectronic aerosol sensor of claim 3, wherein the second plurality of photosensors includes a fourth photosensor beneath a first side of the airflow channel positioned todetect scattering from particles deflected in a first direction in the electric charge region and a fifth photosensor beneath a second side of the airflow channel positioned to detect scattering from particles deflected in a second direction that is opposite the first direction in the electric charge region.

5. The optoelectronic aerosol sensor of claim 4, further including a barrier at least partially encompassing and extending up from the fourth and fifth photosensors.

6. The optoelectronic aerosol sensor of claim 5, wherein the barrier extends 1 mm above the fourth and fifth photosensors.

7. The optoelectronic aerosol sensor of claim 1, wherein the first laser is configured to direct the first beam at an angle of between about 40 degrees and about 50 degrees with respect to a direction of flow of the airflow channel at a point of intersection with the airflow channel.

8. The optoelectronic aerosol sensor of claim 7, wherein the second laser is configured to direct the second beam at an angle of between about 40 degrees and about 50 degrees with respect to the direction of flow of the airflow channel at a point of intersection with the airflow channel.

9. The optoelectronic aerosol sensor of claim 2, wherein the focus spot has a diameter of less than 50 micrometers.

10. The optoelectronic aerosol sensor of claim 1, wherein the first laser has a wavelength of between about 635 nm and 650 nm, the second laser has a wavelength of about 450 nm, and the third laser has a wavelength of between about 375 nm and 380 nm.

11. The optoelectronic aerosol sensor of claim 2, wherein a voltage between the pair of electric charge plates are configured to produce an electric field of 1000 V / cm to 30,000 V / cm.

12. The optoelectronic aerosol sensor of claim 4, wherein the first, second, and third photosensors are photodiodes.

13. The optoelectronic aerosol sensor of claim 12, wherein the fourth and fifth photosensors are photodiodes.

14. The optoelectronic aerosol sensor of claim 2, further including a pair of UV lasers positioned to send beams to the focus spot and a spectrometer positioned beneath the focus spot.

15. The optoelectronic aerosol sensor of claim 14, wherein the plurality of photosensors includes a first photodiode beneath and downstream from the focus spot positioned to detect back scattering and a second photodiode upstream of the first photodiode positioned to detectforward scattering, wherein the spectrometer is between the first photodiode and the second photodiode.

16. The optoelectronic aerosol sensor of claim 3, wherein one or more of the first, second, and third photosensors is a spectrometer.

17. The optoelectronic aerosol sensor of claim 1, further including a flow sensor, a temperature sensor, and a relative humidity sensor.

18. The optoelectronic aerosol sensor of claim 2, wherein the first laser is configured to direct the first beam at an angle of between about 40 degrees and about 50 degrees with respect to a direction of flow of the airflow channel at a point of intersection with the airflow channel.

19. The optoelectronic aerosol sensor of claim 18, wherein the second laser is configured to direct the second beam at an angle of between about 40 degrees and about 50 degrees with respect to the direction of flow of the airflow channel at a point of intersection with the airflow channel.

20. An optoelectronic aerosol sensor comprising: a housing having an inlet port and an outlet port; an air circulation device configured to draw air into the housing through the inlet port, through an airflow channel, and out the outlet port; a first laser for generating a first beam at a first wavelength, the first laser configured to send the first beam through a focus spot in the airflow channel, wherein the focus spot has a diameter of less than 50 micrometers; a second laser for generating a second beam at a second wavelength, the second laser configured to send the second beam through the focus spot; a first photodiode positioned beneath to the focus spot and configured to detect light scattered from particles in the focused spot; a second photodiode positioned upstream from the focus spot and configured to detect light scattered from particles in the focus spot; a third photodiode positioned downstream from the focused spot and configured to detect light scattered from particles in the focus spot; an electric charge region downstream from the focus spot including a pair of charge plates on opposite sides of the airflow channel;a third laser for generating a third beam configured to send the third beam through the airflow channel downstream from the pair of charge plates; a fourth photodiode positioned beneath a first side of the airflow channel downstream from the pair of charge plates configured to detect light scattered from particles deflected toward the first side of the airflow channel; and a fifth photodiode positioned beneath a second side of the airflow channel downstream from the pair of charge plates configured to detect light scattered from particles deflected toward the second side of the airflow channel.

21. The optoelectronic aerosol sensor of claim 20, wherein the sensor has a volume of about 400 cm3.

22. A method for detecting and classifying aerosol particles comprising: drawing air into a sensor housing and through an airflow channel within the sensor housing; directing a first laser beam having a first wavelength at a focus spot in a light scattering region of the airflow channel, wherein the first laser beam is at an angle of about 45 degrees with respect to a direction of flow of the airflow channel; directing, alternatingly with respect to the first laser beam, a second laser beam having a second wavelength, at the focus spot, wherein the second laser beam is at an angle of about 45 degrees with respect to a direction of flow of the airflow channel; detecting light scattered from particles interacting with the first laser beam and the second laser beam at a plurality of photosensors positioned beneath the airflow channel in the light scattering region; applying an electric field across the airflow channel downstream from the light scattering region; directing a third laser beam through the airflow channel downstream from the electric field; and detecting light scattered from particles interacting with the third laser beam at a first photosensor positioned beneath and on a first side of the airflow channel downstream from the electric field and from particles interacting with the third laser beam at a second photosensor positioned beneath and on a second side of the airflow channel downstream from the electric field.

23. The method of claim 22, wherein the first laser beam and the second laser beam have paths that are about 90 degrees from each other.

24. The method of claim 23, wherein each pulse of the first laser beam and the second laser beam have a duration of about 1 ms and are repeated alternatingly.

25. The method of claim 24, wherein the plurality of photosensors includes a first photosensor located beneath the focus spot, a second photosensor located downstream from the first photosensor, and a third photosensor located upstream from the first photosensor.

26. The method of claim 25, further including correlating signals received at the plurality of photosensors with periods when the first laser beam and the second laser beam, respectively, interacted with particles in the airflow channel in the light scattering region.

27. The method of claim 24, wherein the electric field is 1000 V / cm to 30,000 V / cm.

28. The method of claim 24, wherein the first laser beam has a wavelength of between about 635 nm and 650 nm, the second laser beam has a wavelength of about 450 nm, and the third laser beam has a wavelength of between about 375 nm and 380 nm.

29. The method of claim 24, wherein the focus spot has a diameter of less than 50 micrometers.

30. The method of claim 24, further including determining a flow rate of air through the airflow channel.

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