Development of a constant concentration particle source

Particle number standards have been widely adopted to regulate emissions from mobile sources such as vehicles and aircraft, yet no reference aerosol source currently exists for the direct calibration of particle number counters (PNCs). Calibration underpins reliable measurement and is essential for regulatory compliance, ensuring that PNCs perform accurately across their full measurement range. Unlike gas analysers, which can be calibrated directly using readily available, certified gas cylinders, PNCs require more complex procedures due to the dynamic nature of aerosols. Nucleation, coagulation, evaporation, and wall losses make it impossible to store aerosols with stable, known properties, and thus calibration typically relies on real-time aerosol generation and comparison against a reference instrument. This introduces additional uncertainties, where multiply charged particles and instrument noise can affect accuracy, particularly at low concentrations and for small particles.
Recent insights into the dynamics of charged aerosol particles have highlighted new opportunities with the potential to control number concentration by harnessing electrostatic repulsion-a phenomenon whereby charged particles of the same polarity disperse due to self-generated electric fields. By controlling particle charge state and flow dynamics, a constant, stable output concentration governed by fundamental physical limits may be possible.
This project aims to explore this novel approach by combining computational modelling and experimental methods to investigate aerosol generation, particle charging techniques, and charged particle dynamics.

Objectives of the work include:
-Evaluation of particle generation methods from which to generate aerosols of a variety of materials
-Adapt and develop numerical models of particle growth, evaporation, and electrostatic dispersion
-Build and test a prototype of the 'constant concentration' particle generation system to validate the concept

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.