Using oscillatory flow and non-Newtonian media to enhance industrial processing of microalgae and other microswimmers
Lead Research Organisation:
University of Strathclyde
Department Name: Mechanical and Aerospace Engineering
Abstract
The importance of microorganisms is well-documented, both in biological ecosystems and in engineering applications. Microalgae are a particular type of microorganism currently grown on an industrial scale in photo-bioreactors for the production of chemicals, effluent treatment, carbon capture and biofuel production. Microalgae biofuel production in particular has been gaining momentum relative to more traditional feedstocks (e.g. sugar cane) due to potential advantages in terms of sustainability. However game-changing engineering of algae-to-fuel technology, for example in the design of optimised cultivation bioreactors that are really competitive with established fuels, requires a much better rheological understanding and characterisation of algae suspensions.
Because in so-called 'active' suspensions swimming microalgae are able to self-propel using flagella, their interaction with flow fields is far more complex than that of non-motile particles, presenting both an opportunity and a challenge. Exploiting swimming activity could lead, for example, to novel separation and 'steering' methods. Nevertheless despite the recognised potential of novel individual and collective behaviour of swimmers for process engineering, experimental studies on algae suspension rheology remain limited and still present basic puzzles.
This project's aim is to improve significantly our knowledge and understanding of the flow behaviour of swimming algae in complex flow conditions, in particular in oscillatory flows, mixed shear-extension flows and flows in non-Newtonian media such as viscoelastic suspensions. For this purpose, a type of unicellular algae, Dunaliella Salina, will be examined to determine its swimming capabilities under differing stimuli. The work will be primarily experimentally based, with rheology, microscopy and velocimetry methods as a platform to map out the algae's response. We will use key parameters from the experimental data to go on to inform new models of 'microswimmer' transport and diffusion in complex media, through collaboration with modelling and theory experts.
Because in so-called 'active' suspensions swimming microalgae are able to self-propel using flagella, their interaction with flow fields is far more complex than that of non-motile particles, presenting both an opportunity and a challenge. Exploiting swimming activity could lead, for example, to novel separation and 'steering' methods. Nevertheless despite the recognised potential of novel individual and collective behaviour of swimmers for process engineering, experimental studies on algae suspension rheology remain limited and still present basic puzzles.
This project's aim is to improve significantly our knowledge and understanding of the flow behaviour of swimming algae in complex flow conditions, in particular in oscillatory flows, mixed shear-extension flows and flows in non-Newtonian media such as viscoelastic suspensions. For this purpose, a type of unicellular algae, Dunaliella Salina, will be examined to determine its swimming capabilities under differing stimuli. The work will be primarily experimentally based, with rheology, microscopy and velocimetry methods as a platform to map out the algae's response. We will use key parameters from the experimental data to go on to inform new models of 'microswimmer' transport and diffusion in complex media, through collaboration with modelling and theory experts.
Organisations
People |
ORCID iD |
| Mónica Oliveira (Primary Supervisor) | |
| Ewan Rycroft (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509760/1 | 30/09/2016 | 29/09/2021 | |||
| 1960599 | Studentship | EP/N509760/1 | 30/09/2017 | 29/06/2021 | Ewan Rycroft |
| Description | The main focus of my work through the first years of funding has been into the effects of complex fluids on the swimming algae (Dunaliella Salina). The algae are 20 microns is size and are motile at the microscope scale, moving around using arm like appendages called flagella. By changing the viscous, shear thinning and viscoelasticity properties of the fluid in which they swim, we examine the response by the algae and gain understanding of their swimming dynamics. Primarily, we look at velocity data, but other analysis is considered such as: Beating frequencies, orientations and individual stoke dynamics. The main findings of this research to this point involve the effects of viscous and shear thinning fluid behaviour. Increasing the viscosity of the medium results in a power-law decrease of the velocity of the swimmer as the increased viscous forces make it harder to swim. Under further scrutiny, we have observed no stroke or swimming pattern alterations with this increasing viscosity, meaning the algae always exert a constant thrust throughout the fluid and cannot alter their swimming stroke to counteract fluid changes. However, one notable difference is how the beating frequency changes with increased viscosity, reducing at a slower rate than the overall velocity. The reasoning's behind this response are still unclear but likely due to the differences in viscous forces on body and flagella. When the algae are examined under shear thinning effects a significant change in swimming stroke is observed. The non-Newtonian nature of the fluid, and large range of relevant shear rates across the swimmer, leads to changing fluid viscosities around the swimmer. These complex interactions result in an enhanced beating frequency and recovery stroke (the portion of the stroke where the swimmer moves in reverse) of the swimmer. Through the process of characterising fluids to use to understand the effects of fluid properties it's vital the algae do not interact with the fluid biologically. One such fluid that was used in the early stages and found to interact with the swimmer was glycerol. When the algae were suspended in a glycerol solution, they could not maintain their internal osmotic pressure and as a result their morphology and motility was drastically reduced. Therefore, this line of research that was discontinued. To characterise the response of the algae the development of new in-house experimental and post-processing methods were developed. Tracking procedures and soft codes that can extract valuable metrics into the alga's swimming characteristics have been created and are available for use within the university and further afield in the future. The next stage of the research will analyse the effects of viscoelastic influences on the swimmer and the effects under flows, both simple and complex. Preliminary data and discussion have been collected for these stages of the research project. List of conferences presents at: Scottish Fluid Mechanics meeting 2018/19 British society of Rheology Midwinter meeting 2018/19 UK Fluids SIG Biologically active fluids 2018/19 International Soft Matter Conference 2019 |
| Exploitation Route | This research has the potential to enhance the knowledge of microscopic swimming organisms, giving an understanding into the nature of their swimming and how they interact in complex environments. This, in turn, can progress the development of novel micro-robotic swimmers for applications such as controlled nanoscale self-assembly, drug delivery, and bionanotechnology. Furthermore, knowledge of the algae can be used in industrial and commercial areas. These include energy (biodiesel derived from algae), and waste treatment (using algae and bacteria to manufacture feedstock chemicals from waste) and commercial products extracted from algae. On top of the general scope of the research, the procedures, codes and processes have been used by project students and interns within the university. They will be able to further develop on the research conducted thus far with the hope some continue further research through their career. |
| Sectors | Agriculture Food and Drink Energy Healthcare Manufacturing including Industrial Biotechology Pharmaceuticals and Medical Biotechnology |