Measure particles below the optical range (<300 nm) as well as in the ultrafine region (<100 nm).

There is great interest in the measurement of particulate levels in the environment. Current legislation mandates measurements of PM2.5 and PM10 but there is a drive to measure particles below the optical range (<300 nm) as well as in the ultrafine region (<100 nm).
In previous projects we have developed compact sensor techniques for measuring the second moment of the particle distribution (nd2) using UV photoionization and electrometry [1,2]; a new technique using bipolar charging in an inexpensive sensor has been shown to offer an absolute measurement of the first moment (nd) [3,4]. These techniques have been favourably compared to other sensors, including corona-based sensors such as Partector, which use corona discharge, and result in measurements of nd1.1[5].
These two techniques are currently being developed as practical sensors for ultrafines, yet much remains to be done to understand the practical limits and advantages of the two techniques relative to existing systems such as aethalometers. In the case of the photoionization method, there a number of issues which need to be further explored and solutions developed:
- Sensitivity to relative humidity (signal loss)
- Materials sensitivity not fully understood: insensitive to salts, probably sensitive to presence of PAHs
- Understand the correlation between the signal from the photoionization method with other devices (aethalometers, corona ionization) in controlled and uncontrolled field applications.
The (nd) sensor based on low-cost radiation ionization has been demonstrated over a wide range of diameters (40-1000 nm), but the device has yet to be tested with a variety of materials and background gases. A number of topics need to be further investigated, including:
- Comparison of the range of values for mobility ratio of ions (Z+/Z-) relative to previous studies
- Determination of the desirable minimum range of ion concentration and residence time (nit) per unit particle concentration compatible with equilibrium conditions required for the operation of the sensor
- Sensitivity to operating conditions (humidity, background)
- Correlation of signal between the signal from the (nd) method with other devices (aethalometers, corona ionization) in controlled and uncontrolled field applications.

Aerosol science has a significant impact on a broad range of disciplines, extending from inhaled drug delivery, to combustion science and its health impacts, aerosol assisted routes to materials, climate change, and the delivery of agricultural and consumer products. Estimates of the global aerosol market size suggest it will reach $84 billion/year by 2024 with products in the personal care, household, automotive, food, paints and medical sectors. Air pollution leads to an estimated 30-40,000 premature deaths each year in the UK, and aerosols transmit human and animal infections. More than 12 million people in the UK live with lung disease such as asthma, and the NHS spends ~£5 billion/year on respiratory therapies. Many of the technological, societal and health challenges central to these areas rely on core skills and knowledge of aerosol science. Despite this, an Industrial Workshop and online survey (held in preparation for this bid) highlighted the current doctoral skills gap in aerosol science in the UK. Participating industries reported that only 15% of their employees working with aerosol science at doctoral-level having received any formal training. A CDT in aerosol science, CAS, will fill this skills gap, impacting on all areas of science where core training in aerosol science is crucial.

Impact on the UK aerosol community: Aerosol scientists work across governmental policy, industrial research and innovation, and in academia. Despite the considerable overlap in training needs for researchers working in these diverse sectors, current doctoral training in aerosol science is fragmentary and ad hoc (e.g. the annual Fundamentals of Aerosol Science course delivered by the Aerosol Society). In addition, training occurs within the context of individual disciplines, reinforcing artificial subject boundaries. CAS will bring coherence to training in the core physical and engineering science of aerosols, catalysing new synergies in research, and providing a focal point for training a multidisciplinary community of researchers. Working with the Aerosol Society, we will establish a legacy by providing training resources for future researchers through an online training portal.

Impact on industry and public-sector partners: 45 organisations have indicated they will act as CAS partners with interests in respiratory therapies, public health, materials manufacturing, consumer and agricultural products, instrumentation, emissions and environment. Establishing CAS will deliver researchers with the necessary skills to ensure the UK establishes and sustains a scientific and technical lead in their sectors. Further, it will provide an ideal mechanism for delivering Continuing Professional Development for the existing workforce practitioners. The activity of CAS is aligned to the Industrial Strategy Challenge Fund (e.g. through developing new healthcare technologies and new materials) and the EPSRC Prosperity Outcomes of a productive, healthy (e.g. novel treatments for respiratory disease) and resilient (e.g. adaptations to climate change, air quality) nation, with both the skilled researchers and their science naturally translating to long-lasting impact. Additionally, rigorous training in responsible innovation and ethical standards will lead to aerosol researchers able to contribute to developing: regulatory standards for medicines; policy on air quality and climate geoengineering; and regulations on manufactured nano-materials.

Public engagement: CAS will provide a focal point for engaging the public on topics in aerosol science that affect our daily lives (consumer products, materials) through to our health (inhalation therapeutics, disease transmission and impacts of pollution) and the future of our planet (geoengineering). Supported by a rigorous doctoral level training in aerosol science, this next generation of researchers will be ideally positioned to lead debates on all of these societal and technological challenges.