Understanding the vortex fluidic device through the development of a theoretical model and the application of neutron techniques

Author: Timothy Solheim

Solheim, Timothy, 2019 Understanding the vortex fluidic device through the development of a theoretical model and the application of neutron techniques, Flinders University, College of Science and Engineering

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The vortex fluidic device (VFD) is a thin film continuous flow processing platform with a wide range of useful capabilities enabling the environmentally friendly processing of compounds. These capabilities include the refolding of misfolded proteins, the biphasic performance of clean oxidations using bleach, and the performance of chemical reactions using more environmentally friendly reagents. The VFD has also demonstrated the ability to prepare a range of materials, including carbon nanorings from carbon nanotubes, the silica-based material SBA-15, and carbon nano-onions coated with Pt or Pd nanodots. Despite these wideranging capabilities, minimal work has been performed investigating the behaviour of fluid within the VFD.

This thesis involved the development of a mathematical model predicting the shape of the thin liquid film within the VFD, along with the generation of a number of useful formulae enabling the calculation of the residence time of liquid within the device, the maximum volume the device can hold, and conditions which generate the thickest film. These equations were shown to be consistent with equations relating to other related systems, and were applied to previous work within the VFD, providing additional insights.

The shape of the thin film within the VFD was investigated using neutron imaging performed at the OPAL nuclear reactor. Images acquired using short acquisition times showed that the thin film within the VFD usually reaches stability within 5 seconds, and showed that the behaviour of water in the VFD is consistent with the behaviour predicted by the mathematical model. Subsequent high resolution images demonstrated that the model accurately predicts the behaviour of toluene, but not the behaviour of more viscous liquids such as glycerol and propylene glycol. Despite this deviation between experimental and predicted behaviour, an effective method was demonstrated for adjusting the mathematical model using experimental data, enabling the accurate prediction of the shape of the film for more viscous liquids. The behaviour of water when interacting with a hydrophobic surface was shown to not be accurately predicted by the model, likely because liquid-surface interactions are not considered by the mathematical model. Investigations into the behaviour of biphasic systems revealed that at present, neutron imaging is unable to provide significant useful information about the behaviour of biphasic systems in the VFD.

A method for performing Small Angle Neutron Scattering in situ with the VFD was developed, and a preliminary investigation into the behaviour of Pluronic P-123 micelles in the VFD was conducted. The results suggest that the VFD may be influencing the interactions between Pluronic P-123 micelles and water. The potential that the VFD may be influencing solventsubstrate interactions is a hypothesis that has been generated previously on several occasions. Lastly, the mathematical model was successfully used to design scaled-up versions of previous methods for preparing imines and amides within the VFD, increasing production rates up to twenty-fold. Overall, the development of this mathematical model and the demonstration of its accuracy and utility will enable the better understanding of future work within the VFD and the more intelligent design of reaction conditions.

Keywords: Neutron Imaging, Vortex Fluidic Device, Green Chemistry, Continuous Flow Processing

Subject: Physics thesis

Thesis type: Doctor of Philosophy
Completed: 2019
School: College of Science and Engineering
Supervisor: Colin Raston