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Team:UCL/Science/MicroF
From 2014.igem.org
Application of microfluidic techniques to test performance of DPUs in scalable synbio azo-remediation technology
We have designed and tested a novel approach to azo-remediation, which allows sustainable and scalable bioprocessing. Our bioprocess integrates elements from upstream and downstream processing.
In order to develop and improve the functionality of our bioprocess, key steps must be tested to quantify process variables, and allow for preliminary mass transfer calculations and detection of azo dye degradation rates.
We have created microfluidic prototype devices to test the mixing in our reactors, and to test the performance of our novel immobilisation module, allowing for process optimisation and testing, without the burdens of expensive pilot scale testing.
The process testing timeline demonstrates that effective microfluidic testing can be used in replacement to conventional small-scale testing approaches. This is ideal for our project, especially when optimising whole unit operations.
Since our project involves designing a novel bioprocess using whole-cell biocatalysts, we constructed a microfluidic scale immobilisation module to investigate and evaluate our industrial scale module, the video is shown on the right.
Investigation into reactor design and reaction constraints can be performed with ease and with low reagent cost, as all variables are scaled down to a micro-level.
Most importantly, the scale-down can be carried out without losing any of the accuracy or quantification of data output; this is due the number of sensors and control mechanisms which can be integrated into the microfluidic system.
For our microfluidic bioreactor, we will be using a magnetic free floating bar as our mixing system. This is an effective method of mixing at a microfluidic scale, as demonstrated in the video on the right. The video on the left is of a microfluidic chemostat bioreactor designed by Davies et al. 2014 UCL, using a free-floating bar to mix two dyes.
On the left, is an image of a microfluidic device constructed and designed by Lewis Brayshaw; which was then tested using facilities in the UCL Microfluidics and Anatomy Labs.
The images above demonstrate the microfluidic device constructed by Lewis Brayshaw. The device was designed initially using computer-aided design, then constructed using rapid polymer prototyping techniques.
Design & construct of a microfluidic device
We will use rapid polymer prototyping techniques to generate microfluidic chips that will allow us to test our reaction and aid in the construction of a realistic bioprocess, which can be successfully scaled-up for industrial use.
As we optimise and change our bioprocess, we can also quickly design new microfluidic chips that can mimic its development on a micro-scale. For example, it is our goal to integrate multiple downstream steps, such as chromatography, in order to isolate potential useful products. Demonstrating this in a microfluidic system is less time-consuming and far more cost effective than doing so at a larger scale.
Above are some examples of the microfluidics devices developed by our team for use in the lab at the UCL ACBE. The devices are initially designed using AutoCAD (2D and 3D computer-aided design software), once the designs are finalised they can be 3D-printed using the facilities provided by the UCL Institute of Making and UCL ACBE; allowing our bioprocess and laboratory team to experiment and improve designs.
An example of one of our microfluidic devices designed on AutoCAD can be downloaded here. This device utilises the basic concept of mixing the cells and dyes, producing a single output stream; much alike to the bioprocessing concept. During the course of designing the microfluidic device, several key considerations must be taken into account: ability to withstand high pressure without leakage; materials of construction to be inert and transparent; size constraints of inlet and outlet piping; ability to accurately 3D-print the device.
Basic principles of microfluidic technology
Microfluidics is the study, design, and fabrication of devices that can handle and process fluids on the microlitre scale. Over the past few decades, this field has been responsible for many commonly used, and sometimes life-dependant, tools that people rely on. For example, glucose sensors for diabetics, is one of the plethora of handheld devices made available through microfluidics. The tiny volumes involved allow niche environments to be studied (e.g. in understanding stem cells), as well as permitting the development of high throughput screening devices (e.g. in drug discovery and development).
One of the major hurdles in microfluidics is the fact that fluids are very difficult to mix at small volumes as a result of low Reynolds numbers. Reynolds number describes flow patterns in various flow situations; a low Reynolds number indicates laminar flow, whereas a large Reynolds number indicates turbulent flow. Turbulent flow allows highly effective mixing in comparison to laminar flow. However, in microfluidics several device designs are available, which (to a greater or lesser degree) allow sufficient mixing. The flip side of this is that diffusion is often the only method of mixing. This in itself can be very useful, particularly when investigating enzyme kinetics.
The videos above were recorded in the UCL ACBE Microfluidics labs by members of our team. The video on the left is a demonstration of laminar flow across a T-junction microfluidic device. The video on the right demonstrates one of the methods of mixing made possible by microfluidics (herring bone channels etched into the chip).
The image on the right displays the microfluidics set-up used by our iGEM team.
The scope and applications of microfluidics is truly immense and as time goes on, ever increasing amounts of investment is made. With more start-up companies and takeover bids in play, it is clear microfluidics is an exciting and emerging scientific field.
As a powerful biological research tool, microfluidics allows the adaptation of various molecular biology techniques - ranging from on-chip gene synthesis (protein expression from coding DNA) to the screening of protein interactions.
