Characterisation and mitigation of particle emissions from 3D printing processes

Theme: Aerosol Technology / Aerosol Measurement Techniques

The widespread adoption of 3D printing is rapidly increasing the use of desktop printers in businesses, public spaces and homes. However, users may be unaware of how to use this technology safely in terms of indoor air quality. This PhD project will develop emissions sampling and characterisation methodologies, understand emissions formation and transformation processes in real-world 3D printing emissions environments and create solutions to mitigate 3D printing emissions. The project will assist those developing/using 3D printers to develop safe- and sustainable-by-design products with low environmental impact. Findings will be disseminated via publications/conferences, CDT website, social media, public engagement activities.

Lead supervisor: Dr Jose M. Herreros

Healthier indoor environments through low cost source apportionment

Theme: Aerosol and Health

Air pollution is a global killer responsible for approximately 7 million premature deaths per year worldwide. Successful air quality management and control not only requires measurement of air pollution levels, but it also requires information on the sources of air pollution and their relative magnitudes and importance. Without this information, it is impossible to plan and enact cost-effective control measures. By achieving local source apportionment in a lower cost manner, this project will allow source apportionment to be used more widely for regulatory and compliance purposes globally.

Lead supervisor: Prof. Francis Pope

Indoor PM2.5 air quality during the transition to Net Zero Housing: implications for public health and economy

Theme: Aerosol and Health

UK is committed to Net Zero by 2050. The transition to Net Zero Housing is key to this target but it has the potential unintended consequences of increasing indoor PM2.5 pollution, which is an invisible killer. This PhD project will measure indoor PM2.5 changes during domestic retrofitting, using real-life air quality observations before and after intervention. Employing a randomized clinical trial approach and machine learning, the study will assess the impact of retrofitting on PM2.5 exposure and health. The goal is to offer evidence for policy and practice in transitioning to Net Zero housing, prioritising public health.

Lead supervisor: Prof. Zongbo Shi

Quantifying the Role of Droplet Charge in Driving Accelerated Chemistry in Aerosol

Theme: Aerosol Measurement Techniques

Microscopic aerosol particles can exhibit dramatically (million-fold) enhanced reactivity compared to macroscopic solutions. This enhanced reactivity may have widespread implications spanning development of greener synthesis routes, accurately modelling pollutant transformation in the atmosphere, and understanding the origins of life. It is therefore imperative to resolve the unique factors contributing to these observations of accelerated chemistry. One poorly constrained factor is electric fields at the interface driving this unusual chemistry. In this project, the student will explore approaches to measure droplet charge and quantify how reaction rates in picolitre-volume aerosol droplets are affected by variations in droplet charge.

Lead supervisor: Dr Bryan R. Bzdek

Coming in from the cold: exploring factors that contribute to the adaptation and survival of human pathogens during aerosol transmission

Theme: Aerosols and Health

Moraxella catarrhalis, a bacterial pathogen primarily affecting humans, is commonly found in children but less so in adults. It causes respiratory infections and possesses surface proteins that enhance survival in the human body. Interestingly, these bacteria are related to organisms from Antarctic permafrost, which change surface protein expression in cold temperatures. This PhD project aims to examine M. catarrhalis survival in respiratory droplets under varying environmental conditions and assess the role of surface proteins in this process. Additionally, it will investigate how surface protein expression impacts the bacteria’s ability to infect human cells following aerosol transmission.

Lead supervisor: Prof. Darryl Hill

Aerosol deposition and resuspension: Dependence on particle physicochemical properties

Theme: Aerosols and Health

Aerosols exhaled from the respiratory tract start with high water content due to the high relative humidity in the lung. Water evaporates rapidly in the environment leading to changes in particle rheology, phase and composition, and influencing the dynamics of particles on deposition on a surface. Such airborne processing can influence the downstream infectivity of respiratory viruses once deposited on a surface and the potential for resuspension of the aerosol and pathogen. In this project, you will explore the deposition and resuspension dynamics of aerosol particles with varying extent of drying, providing insight into the indirect mode of transmission of respiratory pathogens.

Lead supervisor: Prof. Jonathan Reid

Optical properties of silicate aerosols in extra-solar planets

Theme: Atmospheric and environmental aerosols

Silicate aerosols are found throughout the universe, yet, we have little information on their physical and spectral properties at the temperatures under which they first condense out from the gas phase. This project will conduct laboratory measurements at high temperatures to determine the optical properties and morphology of nano-particle silicates as a function of temperature, particle size distribution and wavelength. Alongside these measurements, a Bayesian inference model will be developed to assess the dependence of the measurements on the experimental conditions and aerosol particles. This project will require practical laboratory measurements and computer science coding skills, with results placed in an astrophysical context. 

Lead supervisor: Dr Hannah Wakeford

Aerosol mediated biofortification

Theme: Aerosol and Health (Biological and Toxicological Responses)

This PhD project explores the use of aerosolized nitrogen-doped carbon quantum dots (N-CQDs), synthesized from agricultural waste, to enhance nitrogen use efficiency (NUE) in crops. By optimizing aerosol generation and delivery, the research aims to improve nitrogen uptake and crop productivity while reducing reliance on traditional nitrogen fertilizers. This study addresses both agricultural sustainability and environmental impact, contributing to advancements in precision agriculture and aerosol science. The project’s findings will provide valuable insights for developing eco-friendly, nutrient-efficient farming systems.

Lead supervisor: Dr Cristina Barrero Sicilia

Bioaerosol monitors for building control systems

Theme: Instrumentation

Join the University of Hertfordshire’s Particle Instruments & Diagnostics group to pioneer a low-cost, real-time bioaerosol detection system. Mold spores in indoor environments pose significant health risks, exacerbated by poor ventilation and high humidity. This project aims to develop and deploy a novel Bio-OPC, capable of identifying harmful bioaerosols in real-world settings.

You’ll work on laboratory calibration, instrument optimisation, and field deployment, collaborating with Siemens to implement this technology in active workplaces. Your research will contribute to safer indoor environments, reducing health risks and improving air quality.

Lead supervisor: Prof. Chris Stopford

Aerosolised nanomaterials and mechanisms of lung fibrosis

Theme: Aerosols and Health

With aerosolised nanomaterials becoming more prevalent from diverse sources, it’s increasingly crucial to comprehend their implications on human health. The focus of this research project lies on lung fibrosis, a severe lung condition often triggered by inhaled nanomaterials, causing lung tissue damage and chronic inflammation. We seek to understand the underlying mechanisms behind fibrosis, thereby enhancing toxicological assessments and facilitating early detection and treatments. This study seeks to redefine our understanding of nanomaterial-induced lung fibrosis, employing diverse methodologies encompassing material characterisation, toxicology, and molecular biology to comprehensively study fibrosis onset and progression post-exposure to nanomaterials.

Lead supervisor: Dr Laura Urbano

Top-down ventilation: improving indoor air quality whilst providing low-energy conditioning of more infection resilient indoor environments

Theme: Indoor air quality

The importance of indoor exposures has been brought to the forefront of attention over recent years, and improving building ventilation is key to managing these exposures. This PhD will explore ‘top-down ventilation’ in which the air flow is brought into rooms at high-level and drawn out near the floor – this can more efficiently remove aerosols. Combining of simple theoretical modelling and laboratory simulations will establish the potential for top-down ventilation to improve indoor air quality whilst providing low-energy conditioning of more infection resilient indoor environments. These potential benefits include enhanced aerosol settling whilst warming the lower part of the room. 

Lead supervisor: Dr Henry Burridge

The role of high altitude aircraft emissions in global surface air quality

Theme: Atmospheric aerosol studies

Aviation is thought to be responsible for significant global public health burdens due to its effects on surface air quality, but this is subject to uncertainty. This is in part because nitrate aerosols – dominant in the estimated impacts– are poorly represented in most global atmospheric models. Furthermore atmospheric changes due to climate feedbacks from aviation aerosol may exceed any chemical effects, making verification of modelled changes difficult. This project seeks to address that challenge, implementing an advanced model of nitrate aerosol into the state-of-the-art UKESM1 Earth system model and using it to evaluate the public health impacts of aviation.

Lead supervisor: Dr Sebastian Eastham

Ice nucleation on atmospheric particles and radiative forcing

Theme: (main) Atmospheric Aerosol Studies, (secondary) Aerosol Measurement Techniques

The research will understand how soot particles from aeroengines or other atmospheric particles contribute to ice nucleation under laboratory simulated atmospheric conditions to evaluate formation of contrail clouds. High speed imaging will quantify the temporal evolution of ice nucleation on ultrasonically levitated particles and quantify the effects of initial particle material, shape, size and environmental conditions on icing growth rate and ice-particle structure. White light illumination of suspended ice-particles will quantify light absorption and scattering and correlate them to ice-particle structure. The unique measurements will be incorporated in computer models to evaluate the impact of atmospheric ice-particles on global warming.

Lead supervisor: Prof. Yannis Hardalupas

Multiscale Models for Synthesis of Tailor-Made Nanoparticles for Advanced Applications

Theme: Basic aerosol Processes

Aerosols synthesised in fluid flows have multiple uses including batteries, tires, solar cells and gas sensors for lifestyle diagnostics. The value of such products depends a lot on particle size and morphology. Therefore, control over these characteristics allows synthesis of tailored nanoparticles for novel applications. The group of S. Rigopoulos has developed unique methods for population balance modelling, which is a method for predicting size and morphology distributions. The objective of this project is to harness these methods, in conjunction with computational fluid dynamics (CFD) and molecular simulations, to provide a multiscale approach for development of controlled nanoparticle synthesis.

Lead supervisor: Dr Stelios Rigopoulos

Ultrafine particles abatement from green infrastructure

Theme: Aerosols and Health

Green Infrastructure (GI) serves as a passive method to mitigate exposure to roadside vehicular emissions, including airborne ultrafine particles (≤100nm; UFPs) that have significant health implications despite being unregulated.

This project aims to investigate the interactions between UFPs and urban GI in roadside environments, with a specific focus on UFP number and surface area.

The objectives will be achieved through a combination of novel field studies to understand the competing influences of particle transformation processes, laboratory investigations for physico-chemical characterisation of UFPs, and utilising the acquired knowledge to propose best practice recommendations for holistic urban GI planning.

Lead supervisor: Prof. Prashant Kumar

The potential for air conditioning systems to recirculate pathogens

Theme: Aerosol Technology / Atmospheric Aerosol Studies / Aerosols and Health

In this project, we will clarify whether pathogens circulated through HVAC systems can increase infection transmission for different building system configurations. It is expected that indoor transmission through HVAC systems operations can be affected by many parameters, including proximity of the particle emission source (infected human) to return air, amount of fresh air added to the system, filters used in air handling units, frequency of cleaning/changing filters, variation in the number of occupants, and changes to airflow pathways due to changes in furniture/equipment location. The outcomes of this study are crucial to inform decisions on future HVAC and building philosophies. If COVID-19 and other respiratory diseases can spread through ventilation systems, strategies such as increasing fresh air supply and technologies such as ultraviolet (UV) germicidal irradiation could become critical and their effectiveness as part of the building system needs to be understood.

Lead supervisor: Prof. Lidia Morawska

Mechanistic study of how viruses such as SARS-CoV-2 and flu do or do not survive long enough in aerosols to be transmitted across the air

Theme: Aerosols and Health

Pandemics are caused by respiratory viruses (COVID-19, flu) that spread in aerosols. These pandemics hit us at a rate of about one pandemic per century, and cause about 10 million deaths/pandemic. Despite this, we know surprisingly little about how viruses spread in aerosols. The PhD will use state-of-the-art experimental aerosol science and molecular biology to investigate the mechanism by which viruses are destroyed by the sudden drying in an aerosol. For example, is it the virus’s spike protein that is destroyed by drying? The project is interdisciplinary in nature. It will involve producing proteins and viruses, and quantifying their survival after aerosol drying.

Lead supervisor: Dr Richard Sear

AI models for airborne particulate matter forecasting in urban areas

Theme: Atmospheric Aerosol Studies

People are often exposed to hazardous levels of particulate matter (PM) concentrations while performing daily activities, inadvertently putting their health and wellbeing at risk. Artificial intelligence (AI) has been a game-changer in several areas of knowledge, including atmospheric sciences. Thus, this project aims to develop novel data-driven and physics-informed AI models based on state-of-the-art deep learning techniques to predict the concentrations of PM at urban scale under desired intervention scenarios, with improved performance and less computational requirements, using Guildford Living Lab as a case study to validate the solution against conventional models such as the ADMS-Urban.

Lead supervisor: Dr Erick G. Sperandio Nascimento