Evaporative Drying of Droplets and the Formation of Micro-structured and Functional Particles

Lead Research Organisation: University of Bristol
Department Name: Chemistry

Abstract

The drying of liquid droplets is a complex process with a wealth of dynamics occurring inside the liquid phase. The effect of these internal processes is to change the distribution of materials in the particle that is formed after drying. These processes are important in a wide range of applications from spray drying processes that form functionalised and micro-structured particles, crop spraying and to the dynamics of particles during inhalation therapies. In this project we will explore the drying kinetics of isolated droplets in air using a range of unique single particle experimental tools. In particular, measurements will use an electrodynamic balance to directly probe the time-evolving size and morphology of droplets during drying with time-resolution as high as 10 ms. The steady equilibrium viscosity and surface tensions of droplets will be interrogated with varying droplet composition using aerosol optical tweezers. We will seek to understand how droplets dry and provide a quantitative approach to measure, predict and interpret the dynamics of droplet evaporation. For example, we will address questions such as when do you get a solid particle or a hollow particle, a uniform particle or one with shells? When formed, are the particles crystalline or amorphous, are different components mixed or separated?

Publications

10 25 50
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Gregson FKA (2019) Studies of competing evaporation rates of multiple volatile components from a single binary-component aerosol droplet. in Physical chemistry chemical physics : PCCP

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Gregson FKA (2019) Drying Kinetics of Salt Solution Droplets: Water Evaporation Rates and Crystallization. in The journal of physical chemistry. B

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Ordoubadi M (2019) Multi-Solvent Microdroplet Evaporation: Modeling and Measurement of Spray-Drying Kinetics with Inhalable Pharmaceutics. in Pharmaceutical research

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509619/1 30/09/2016 29/09/2021
1793186 Studentship EP/N509619/1 30/09/2016 30/03/2020 Florence Gregson
 
Description We have studied particle formation in rapidly evaporating aerosol droplets: aqueous droplets containing solutions of inorganic or organic solutes or mixtures. We studied how evaporation rates vary depending on the processing conditions, and how this can strongly affect the crystallisation of inorganic components. For example, with sodium chloride droplets, low concentrations of droplets evaporating into high temperatures evaporate much quicker than high concentrations or lower temperatures, and significant surface enrichment can occur at the droplet surface. This leads to highly monodisperse, hollow, crystalline particles. Alternatively, other solutions such as sodium nitrate, evaporate in a highly non-reproducible fashion with some droplets crystallising and others forming amorphous particles. By tuning the drying temperature, humidity, concentration of sodium nitrate, and the presence of additional co-components, we can predict and control the degree of crystalline or amorphous particles formed. This is very useful for those in the spray-drying field to be able to better control their product morphology for a desired application.
Exploitation Route In the field of spray-drying, it is crucial to be able to control the product morphology of the powder particles. Some applications may need a highly crystalline product, or a very soluble product, or a very low density (for e.g. good aerodynamic properties for lung delivery of pharmaceutical powdered drugs). Industrial partners will be able to take our findings to better understand particle formation in their spray-dryers to hence fine-tune their drying conditions for a desired powdered product. In the wider sense, knowledge about the mechanisms behind particle formation from liquid droplets is highly useful for producing particles for fuel cell applications, for agricultural crop-spraying, and inkjet printing.
Sectors Agriculture

Food and Drink

Manufacturing

including Industrial Biotechology

Pharmaceuticals and Medical Biotechnology
 
Description Our findings lead to some collaborators in industrial sectors (such as spray-drying companies, crop-spraying, pharmaceutical and inkjet printing) to better understand how their droplets evaporate under different conditions to lead to better product control. In addition, we performed some work on how rapid volatile solvents evaporate under humid atmospheres which is highly useful for inhaler technology. We reported these findings at various conferences and meetings and some pharmaceutical companies were very interested in this work.
First Year Of Impact 2017
Sector Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology
Impact Types Economic
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation AkzoNobel
Country Netherlands 
Sector Private 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation Bristol-Myers Squibb
Country United States 
Sector Private 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation Centre for Process Innovation (CPI)
Country United Kingdom 
Sector Private 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation Chiesi
Country Italy 
Sector Private 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation Croda International
Country United Kingdom 
Sector Private 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation Danone
Department Nutricia Ltd
Country United Kingdom 
Sector Private 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation Durham University
Country United Kingdom 
Sector Academic/University 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation Inca Digital Printers Ltd
Country United Kingdom 
Sector Private 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation Nestlé (Global)
Department Nestlé UK
Country United Kingdom 
Sector Private 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation Sun Chemical Ltd
Country Canada 
Sector Private 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation Syngenta International AG
Country Switzerland 
Sector Private 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about droplet drying: comparison between spray dryers and droplets on surfaces 
Organisation University of Leeds
Country United Kingdom 
Sector Academic/University 
PI Contribution We take measurements on droplets drying in free air (levitated) using our instrumentation and regularly report our results to our partners at collaborative meetings.
Collaborator Contribution Our university collaborators take measurements of droplets drying on flat surfaces or of modelled droplets in spray-dryers and compare their results with ours at collaborative meetings. The industrial partners attend these meetings to discuss our results and comment on any issues in their processes which we could investigate in experimental measurements. Occasionally our industrial partners provide us with their own materials (e.g. milk powder, paint) for us to study droplet drying with in our instruments.
Impact This collaborative partnership has led to useful sharing of ideas and solving experimental problems. It also gives us direction about what interesting systems to try in our experiments so that we can better compare our results.
Start Year 2016
 
Description Collaboration about inorganic droplet evaporation and crystallisation 
Organisation University of Bristol
Department School of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution We provided experimental data on droplet evaporation using our instruments in the School of Chemistry.
Collaborator Contribution Our collaborators at the School of Physics used our data to fit to a model, to gain greater insights into the physics of crystallisation.
Impact We published a paper in a journal: Gregson, F. K. A.; Robinson, J. F.; Miles, R. E. H.; Royall, C. P.; Reid, J. P. Drying Kinetics of Salt Solution Droplets: Water Evaporation Rates and Crystallization. J. Phys. Chem. B 2018, 123, 266-276. DOI: 10.1021/acs.jpcb.8b09584
Start Year 2017
 
Description Collaboration about multi-component solvent evaporation 
Organisation University of Alberta
Department Faculty of Engineering
Country Canada 
Sector Academic/University 
PI Contribution Experimental measurements on the evaporation of liquid aerosol droplets containing multiple volatile components. We collected all experimental data and shared it with our collaborators.
Collaborator Contribution Our partners in Canada performed modelling work, to model our data and hence build a greater understanding of the microphysics at play in evaporating droplets.
Impact Submission of two recent scientific publications.
Start Year 2017