Crystallisation in nano-droplets

Lead Research Organisation: University of Bath
Department Name: Chemistry


We will design and develop a machine to obtain information about the timescales and processes behind the self-assembly of phases in aerosols. Once built, experiments will progress through increasing levels of complexity, starting with basic verification of the correct functionality of the apparatus through to detailed analysis of atmospherically, industrially, or pharmaceutically relevant applications making use of evolving, environment-dependent, aerosol phases.
Aerosols are present in all walks of life and often contain molecules which are capable of forming complex phases through processes known as self-assembly. As solvents are taken up and released by the system, the molecules can adopt different shapes and conformations, known as lyotropic phases. The variation of these phases is a widely researched topic with various applications such as the development of smart materials. Similarly, aerosol science is a rapidly developing area of research, not only in the context of the current SARS-CoV-2 epidemic but also in fields such as industrial spray drying, atmospheric processes and inhaled drug delivery. However, rarely are these two domains considered simultaneously; the self-assembly of complex phases in aerosols is often overlooked, which is an unfortunate oversight caused by a lack of interdisciplinary communication.
This project aims to link these two fields by developing a platform to study the self-assembly of amphiphiles in aerosols, both at equilibrium and during the formation of the phases. This platform will consist of a piezo-electric droplet-on-demand generator which will produce a droplet containing molecules which are known to self-assemble. This droplet will then go on to be trapped in an electrodynamic balance where the relative humidity in the levitation chamber will be controlled in real time. Small angle X-ray scattering data will be collected on the droplets as a function of suspension time and of relative humidity.
Using the time-resolved scattering data, we will be able to elucidate the timescales over which self-assembly occurs in aerosols. In turn the timescales and changing structure as the system moves towards equilibrium will allow us to draw conclusions as to the processes by which they form. Understanding these processes and the timescale on which they act is key to determining the potential impact of these systems. For example, we will know which phase is deposited in the lung for an inhaled drug, or the morphology produced when spray drying a certain solution, provided we know the time allowed for equilibration and the conditions of the environment. This will improve the effectiveness of medical interventions and the reliability of industrial processes.

Planned Impact

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.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S023593/1 31/03/2019 29/09/2027
2436244 Studentship EP/S023593/1 30/09/2020 29/09/2024 Jack MACKLIN
Description Lung surfactant self-assembles in droplets at humidities commonly found indoors. This has implication for virus transmission.
Exploitation Route Studies on exactly how this self-assembly affects transmission are vital.
Sectors Environment


Title ACoustic levitation of resipiratory droplet for study with synchrotron radiation in RH controlled environment 
Description Dropelts were intorudced into an acoustic levitator via a droplet on demadn system, allowing control over their size. These contained lung surfactant. The RH was varied while the droplets were studied with small and wide angle x ray scattering (SAXS/WAXS) and the change in phase of the droplet was tracked. 
Type Of Material Improvements to research infrastructure 
Year Produced 2024 
Provided To Others? No  
Impact Lung surfactant self assembles in a humidity dependent manner. Full analysis and publication not yet complete. 
Title Complementary Dynamic vapour sorption and humidified capillary small angle X-Ray scattering 
Description The use of DVS and SAXS in capillaries containing air of known humidity to develop phase diagrams for surfactant thin films. 
Type Of Material Improvements to research infrastructure 
Year Produced 2023 
Provided To Others? No  
Impact None yet, Data collection still in progress 
Title Falling droplet column in synchrotron 
Description A falling droplet column was used to study shortly aged particles as they fell in a controlled path in controlled RH environment. 
Type Of Material Improvements to research infrastructure 
Year Produced 2023 
Provided To Others? No  
Impact Analysis of data not yet complete 
Title Humidity controlled polarising micrscopy 
Description Use of a humidity controlled chamber and polarising micrscopy to study the phase behaviour of surfactants 
Type Of Material Improvements to research infrastructure 
Year Produced 2023 
Provided To Others? No  
Impact None yet, data collection in progress 
Title Synchrotron based electrodynamic levitation 
Description Use of an electrodynamic balance in a synchrotron to study levitated droplets' structure 
Type Of Material Improvements to research infrastructure 
Year Produced 2023 
Provided To Others? No  
Impact Discovery of ionsing raidation preventing levitation - full descirptive and analytical paper in preparation 
Description Research in acoustic levitation and X-Ray diffraction 
Organisation Malvern Panalytical
Country United Kingdom 
Sector Private 
PI Contribution Wokr on building acoustic levitators as a support for in lab based x-ray diffraction
Collaborator Contribution Materials and training provided.
Impact Paper submitted, yet to be published.
Start Year 2023