Active Particles in Colloidal Liquid

Lead Research Organisation: University of Oxford
Department Name: Oxford Chemistry

Abstract

Active particles have been an area of great interest in the past decade. Not only do their motions and behaviours provide interesting ways to develop the science
of non-equilibrium dynamics, they are also relevant in the study of animate objects on the macroscale; such as birds, crowds and bacteria. Despite having been at the front of recent colloidal research very little is know about the specifics of their interactions with their environments. There are many examples of experimental systems that not only express the typical characteristics of active motion, but also have their own peculiar facets. I intend on investigating how certain active particles behave and interact with a system of colloidal rods. Lachlan would like to both discover more about how the colloidal liquid crystals affects the active particles and how in turn the liquid crystal is affected. To achieve a colloidal liquid crystal Lachlan will use rod shaped silica particles and the FD virus (a virus also shaped as a rod). In the silica system he will use other active silica particles half coated in specific metals, both rods and spheres, and propel them using the well known AC current method or with the catalysed decomposition of hydrogen peroxide. For the FD virus liquid crystal Lachlan intend on using a certain strain of the Bacillus subtilis bacteria. Specifically it would be interesting how the aspect ratio of the colloids affect the system as well as the size ratio between the liquid crystal blocks and the active particles. Using different shapes of active particles may prove interesting to show how the excluded volume of the liquid crystal, caused by a miss-match between the active and passive particles, may thermodynamically alter their behaviour. Although in previous work the three active systems have been mostly categorised and cases have been observed where the presence of a molecular liquid crystal has affected the motion of active particles, in these cases the size of the blocks of the liquid crystal has been several orders of magnitude smaller than the size of the active matter. Therefore, investigating the region where the size of the blocks of the liquid crystal is similar to the active component of the system is new and may provide new complex phenomena in the interplay of the particles. It is hoped to achieve, with this project, a furthered understanding of not only the specific system that Lachlan will be working with but to bring that knowledge and be able to apply it to a broader scope of physical phenomena. Cells, for example, are a complex mix of microscale or nanoscale structures which can interact to form pseudo liquid crystals and therefore studying the interaction of active particles in similar environments could give insights to intracellular transport or even how to deal with viral or bacterial infections. At this stage, the field of active particle research has been very successful in providing theoretical simulations and the predictions of certain useful phenomena and we hope to provide some experimental grounding to them. Furthermore, in the long term it may be possible to create devices or materials with specific tunable functions. The most obvious use for synthetic active particles is to make a targeted drug delivery system.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509711/1 01/10/2016 30/09/2021
1950179 Studentship EP/N509711/1 01/10/2017 30/09/2020 Lachlan Charles Alexander
 
Description Active Brownian Dynamics simulation is a method to generate a system of active particles with a computer. These can be used to understand complicated out of equilibrium systems. We have shown that "hard interactions" between particles used in the literature so far fall short of being optimal for such systems. We developed a new method of simulating hard interactions which resolves all issues related to this.

We have also optimised an experimental system of electrophoretic active particles for general use. This to show how the electrode, salts and particle properties affect the system's behaviour.
Exploitation Route Publications and methods to be used in further research
Sectors Other

 
Description Universidad Complutense de Madrid 
Organisation Complutense University of Madrid
Country Spain 
Sector Academic/University 
PI Contribution Comments and collaboraiton on the study of active Brownian dynamics simulations.
Collaborator Contribution Comments and verifying our methods fit with literature and current understanding.
Impact Hopefully joint papers soon.
Start Year 2018