A miniature Atmospheric Particle Classifier (APC)

Lead Research Organisation: University of Hertfordshire
Department Name: Science and Technology RI

Abstract

The single greatest source of uncertainty in the estimates of climate sensitivity to either natural or man-made changes continues to be clouds (IPCC 2001, 2007). Much of this uncertainty arises from the lack of information relating to the properties of smaller cloud particles (droplets, ice crystals) and aerosol. These particles directly and indirectly affect how much sunlight the clouds reflect back into space (ie: cooling the Earth) and how much infrared or heat radiation from the Earth's is trapped (ie: warming the Earth). Climate scientists therefore need accurate information on the sizes, shape, and abundance of these different types of atmospheric particle so that the effect of cloud properties on our future climate can be predicted. Cloud microphysicists have at their disposal several types of in-situ instrument for counting and sizing atmospheric particles down to sub-micrometre sizes, whilst other instruments can capture real images of larger individual particles. Such images are especially valuable as they provide detailed particle shape data, but instrument optical aberrations and depth of field limitations result in image blurring, restricting such imaging techniques to particles greater than ~25um in size. The greatest lack of knowledge, and therefore potentially the greatest source of uncertainty, surrounds smaller particles, such as ice crystals down to a micrometre in size, well below the resolution limits of cloud particle imaging probes. An alternative approach that can provide detailed information on these smaller cloud particles is that of spatial light scattering, in which the unique patterns of light scattered by individual particles passing through a laser beam is recorded and analysed. In the past, the University of Hertfordshire has developed several types of aircraft instrument based on spatial light scattering (so called SID probes) and these have been procured by meteorological research organisations in the USA, UK, and Europe. However, SID probes are large (each requiring a 'PMS' wing-mounted canister) and expensive (>£80k). This limits their deployment to the relatively small numbers of research aircraft that carry PMS canisters (and where competition for such canisters is normally intense). This Proof-of-Concept proposal therefore seeks to address this by developing a small, low-cost (<£3k) and light-weight (<1kg) 'miniature SID' sensor, referred to as the Atmospheric particle Classifier. The APC would exploit recent major technological advances in diode laser and detector array technologies developed for mass consumer markets (such as DVD R/RW players, security systems, etc.) to achieve similar performance to the predecessor SID probes but at a small fraction of the cost, size and weight. The APC would count, size and classify atmospheric particles down to micrometre sizes at rates of several thousand per second, differentiating droplets, solid aerosol, and ice crystals on the basis of shape and determining the extinction coefficient of each particle (an important parameter in understanding cloud radiative properties). The sensor would be small enough to be borne by balloon or UAV, or to be part of a combination probe in a single PMS canister (potentially freeing other PMS mountings). It could potentially be carried by civilian passenger aircraft, thus generating a huge source of cloud data. Beyond this, the APC could also find wider application in general aerosol monitoring (see 'Beneficiaries') in areas of environmental health, pollution monitoring, etc., where a knowledge of the aerosol's constituent particle types is essential. The APC sensor would built and tested at UH, with performance validation and calibration being carried out by the University of Manchester in their cloud simulation chamber. The finished APC would become available for use by all of the UK science community through NERC's Facility for Ground-based Atmospheric Measurement (FGAM).

Publications

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Hesse E (2015) Modelling light scattering by absorbing smooth and slightly rough facetted particles in Journal of Quantitative Spectroscopy and Radiative Transfer

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Hesse E (2012) Modelling diffraction by facetted particles in Journal of Quantitative Spectroscopy and Radiative Transfer

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Martin W (2010) Polarized optical scattering signatures from biological materials in Journal of Quantitative Spectroscopy and Radiative Transfer

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Robinson N (2013) Cluster analysis of WIBS single-particle bioaerosol data in Atmospheric Measurement Techniques

 
Description The particle detection technology developed for the Airborne Particle Classifier has significant potential in low-cost particle detection in application areas such as air quality monitoring, occupational aerosol monitoring, industrial aerosols, etc. Because of this, a sensor company have taken a licence to the technology (based on patents filed) with a view to commercially producing a low-cost airborne particle 'engine' that could be implemented in a wide variety of these application areas.
First Year Of Impact 2010
Sector Environment
Impact Types Societal

 
Description Commercial funding
Amount £98,000 (GBP)
Organisation Alphasense 
Sector Private
Country United States
Start 11/2014 
End 11/2015
 
Description Detecting Man-made Mineral Fibres
Amount £8,000 (GBP)
Funding ID PJC4044 
Organisation Morgan Advanced Materials 
Sector Private
Country United Kingdom
Start 12/2016 
End 02/2017
 
Description MBS Aerosol Science
Amount £89,303 (GBP)
Organisation Stockholm University 
Sector Academic/University
Country Sweden
Start 09/2017 
End 09/2018
 
Description Particle Phase Discriminator instrument development.
Amount £58,000 (GBP)
Organisation ETH Zurich 
Department Institute for Atmospheric and Climate Science
Sector Academic/University
Country Switzerland
Start 01/2015 
End 09/2015
 
Description Real-time Airborne Asbestos Detection Technology Sevelopment
Amount £97,110 (GBP)
Funding ID PJC4099 
Organisation ALERT Technology Ltd. 
Sector Private
Country United Kingdom
Start 01/2017 
End 12/2017
 
Description Research funding for 'Pocket PM' personal air quality sensor development
Amount £86,000 (GBP)
Organisation Alphasense 
Sector Private
Country United States
Start 02/2017 
End 02/2018
 
Description Wide Issue Bioaerosol Spectrometer development
Amount £33,063 (GBP)
Funding ID PJC003904 
Organisation University College Cork 
Sector Academic/University
Country Ireland
Start 03/2015 
End 08/2016
 
Title AN IMPROVED LOW COST APPARATUS AND METHOD FOR THE DETECTION OF A FLUID-BORNE PARTICLE 
Description An apparatus for the detection of a fluid-borne particle (10) in an optically defined particle sensing zone, the apparatus comprising: i) a scattering chamber (40); ii) a means for providing a sample of fluid (34), containing the fluid-borne particle, in the form of a flow through the optically defined particle sensing zone;iii) A means for generating a beam of radiation (12) through the optically defined particle sensing zone;iv)a single reflector or refractor (14) means having a primary focus (16) within the optically defined particle sensing zone and a secondary focus (20) located outside the beam of radiation; v) a detector means comprising a first photosensitive detection area (26) a second photosensitive detection area (29); vi) a means for deriving area from the radiation detected by the first photosensitive detection area and second photosensitive detection area of the detection means wherein the single reflector or refractor means is adapted to direct radiation scattered from the fluid borne particle passing through the beam of radation within the optically defined particle sensing zone to the detection means located at the secondary focus of the single reflector or refractor means and the optically sensing zone comprises a first and a second zone. 
IP Reference WO2012056217 
Protection Patent granted
Year Protection Granted 2012
Licensed Yes
Impact The particle detection technology developed for the NERC Airborne Particle Classifier project is now being exploited in the NERC Network of Sensors project 'High density sensor network system for air quality studies at Heathrow airport', (Universities of Cambridge, Hertfordshire, Manchester, Imperial, plus NPL and CERC). This project will see more than 70 of the Hertfordshire particle detectors positioned in a ground-breaking project around the perimeter of Heathrow airport to undertake long-ter
 
Title Detection of a fluid-borne particle using optical scattering 
Description Detecting the size and concentration of fluid-borne particles using optical light scattering. A flow of particles 10 passes through laser beam 12 in a scattering chamber. A single reflector or refractor means such as an elliptical or spherical mirror 14 is positioned such that its primary focus 16 lies on the axis of the laser beam 12 in an optically defined particle sensing zone. Scattered light from the particles in the optically defined particle sensing zone is reflected by mirror 14 to photo-detector 24 placed at the secondary focus 20 of the mirror 14. The photo-detector 24 comprises two photosensitive detection areas 26, 28. Means are provided for deriving data from the radiation detected by the first photosensitive detection area 26 and second photosensitive detection area 28 of the detection means. Therefore the elliptical mirror 14 and photo-detector 24 provide a method of optically defining a sensing zone within the illuminating laser beam. 
IP Reference GB2484930 
Protection Patent granted
Year Protection Granted 2012
Licensed Yes
Impact The technology has been licensed to Alphasense Ltd (Braintree, UK) who are now manufacturing products such as their OPC-N2 PM sensor which is being sold worldwide.They are being supplied to the Change London 'AirSensa' project that will eventually comprise a network of 10,000 sensors across London, possibly the largest air quality network in the world. (http://www.changelondon.org/projects.php# ). They are also being used in the UNEP (United Nations Environment Programme) initiative, funded by
 
Title Detection of fluid-bourne particles 
Description An apparatus for the detection of a fluid-borne particle in an optically defined detection zone, comprises a scattering chamber 3, a fan 1 for providing a sample of fluid, containing the fluid-borne particle, in the form of a flow through the optically defined detection zone and a laser beam generator 5 for generating a beam of radiation through the optically defined detection zone 5. There is also a first reflector or refractor means 8a, a second reflector or refractor means 8b; a first detector means 11; a second detector means 12 and a means for deriving data from the radiation detected by the first and second detection means. 
IP Reference GB2474235 
Protection Patent granted
Year Protection Granted 2011
Licensed Yes
Impact The technology is sufficiently cheap to allow multiple fog monitors to be deployed across an area. This opens up new opportunities for studying fog formation and lifetimes, aiding hazard weather warnings and the development of fog dispersion methodologies.
 
Title Detection of fluid-bourne particles 
Description An apparatus for the detection of a fluid-borne particle in an optically defined detection zone, comprises a scattering chamber 3, a fan 1 for providing a sample of fluid, containing the fluid-borne particle, in the form of a flow through the optically defined detection zone and a laser beam generator 5 for generating a beam of radiation through the optically defined detection zone 5. There is also a first reflector or refractor means 8a, a second reflector or refractor means 8b; a first detector means 11; a second detector means 12 and a means for deriving data from the radiation detected by the first and second detection means. 
IP Reference GB2474235 
Protection Patent granted
Year Protection Granted 2011
Licensed Yes
Impact This technology is now being used in the development of personal aerosol monitors (lapel worn) that will be deployed in large numbers to allow epidemiological studies of the effects of air particulate pollution on health.
 
Title Fluid-borne Particle Detector 
Description An apparatus and method for the detection of a fluid-borne particle 
IP Reference US20100328665 
Protection Patent granted
Year Protection Granted 2010
Licensed Commercial In Confidence
Impact tbc
 
Title Second Generation Low-Cost Particle Counter 
Description An apparatus for the detection of a fluid-borne particle (10) in an optically defined particle sensing zone, the apparatus comprising: i) a scattering chamber (40); ii) a means for providing a sample of fluid (34), containing the fluid-borne particle, in the form of a flow through the optically defined particle sensing zone; iii) A means for generating a beam of radiation (12) through the optically defined particle sensing zone; iv) a single reflector or refractor (14) means having a primary focus (16) within the optically defined particle sensing zone and a secondary focus (20) located outside the beam of radiation; v) a detector means comprising a first photosensitive detection area (26) a second photosensitive detection area (29); vi) a means for deriving area from the radiation detected by the first photosensitive detection area and second photosensitive detection area of the detection means wherein the single reflector or refractor means is adapted to direct radiation scattered from the fluid borne particle passing through the beam of radiation within the optically defined particle sensing zone to the detection means located at the secondary focus of the single reflector or refractor means and the optically sensing zone comprises a first and a second zone. 
IP Reference US2013229655 
Protection Patent granted
Year Protection Granted 2013
Licensed Yes
Impact The low-cost OPC technology is now being commercially produced by Alphasense Ltd, Essex UK. (http://www.alphasense.com/index.php/air/) by the name 'OPC-N2'. Units are being provided to the Change London 'AirSensa' project (http://www.changelondon.org/projects.php) that will ultimately see 10,000 networked OPC-N2 units deployed across London to monitor air quality. The units have also been selected by the United Nations Environment Programme, funded by the World Bank, for deployment in third-wor
 
Title Software for the analysis of air quality data from extremely dusty environments. 
Description The low-cost air quality sensor technology developed by the University of Hertfordshire and now licenced to Alphasense Ltd (reported elsewhere) has been used by Trolex Ltd in their safety-critical air quality monitors for extreme environments such as mines and tunnel constructions. These units have been deployed, for example, in the Crossrail Tunnel project in London, the largest civil engineering project in Europe. They monitor dust levels so high that conventional commercial dust monitors quickly become clogged and inoperable. Analysing the results from the monitors required special software to be written by Hertfordshire for Trolex Ltd, and this became the subject of a licensing agreement between the two organisations signed in 2016. 
IP Reference  
Protection Copyrighted (e.g. software)
Year Protection Granted 2016
Licensed Yes
Impact None yet.