Responsive Aerosol: A Design Framework for Aerosol with Required Properties

Aerosol are naturally responsive to their environment; changes in temperature, relative humidity (RH), gas phase composition and many other conditions can illicit changes in the aerosol such as size, rheology, composition, and phase. This project aims to characterise the changes in an aerosol's properties in response to an external stimulus, and to, ultimately, build a framework to allow the design of aerosol that have a specific, desired response to a known stimuli. Polymers can be designed to exhibit response to stimuli; for example thermoresponsive hydrogels, which undergo a transition from solution to gel as the temperature is raised, or polymers with variable glass transition temperatures, which transition from a hard, brittle solid to a soft, malleable material as temperature is raised. The polymers investigated in this work are poloxamer 407, poly(N-isopropylacrylamide) (pNIPAM), and a variety of monodisperse nanoparticles comprised of di-block copolymers. Aqueous solutions of these polymers are dispensed into micrometre-sized droplets using a droplet-on-demand dispenser, and probed using the comparative kinetics electrodynamic balance (CK-EDB) to investigate the effect of varying external stimuli such as temperature and RH on the evaporation kinetics. The Single Aerosol Drying Kinetics and Trajectory (SADKAT) model is used to model the evaporation profiles of these droplets under the same environmental conditions to provide a comparison to water evaporation kinetics. To investigate the impact of the external stimuli and evaporation kinetics on the final morphology of the dried microparticles, the aqueous droplets are dried in a falling droplet column (FDC) under the same conditions as used in the CK-EDB, and collected on a glass slide which is imaged using scanning electron microscopy (SEM).

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.