Team:Queens Canada/Fluorometer
Fluorometer
A fluorometer is a device that can measure the amount of visible light that fluoresces (gets excited by a certain wavelength of light and immediately emits another wavelength of light). Quantities of fluorophores such as GFP (green fluorescent protein) and mNeonGreen can be detected using a high-sensitivity light sensor in conjunction with various optical components. Many existing fluorometers are used in a laboratory setting, where the device can be set up on a benchtop or lab desk. For this project, the aim was to make the device handheld for law enforcement officers to be able to perform roadside tests.
Design Considerations
Optics
Conventional fluorometers can have many precise components such as optical filters, collimating lenses, and high-powered lasers. However, to make the fluorometer portable and accessible, the size and cost of many of these components was reduced or eliminated. The optical design of this prototype consists of only a coloured LED and a light sensor. The LED (light emitting diode) must match the excitation wavelength of the specific fluorophore being examined. For the purposes of this project, GFP was used as the major fluorophore in question. GFP has an excitation wavelength peak of 490nm, which means that the optimal LED to use to excite the fluorophore would be a 490nm LED. The range of excitation wavelengths for GFP can be shown in the figure below along with the range of emitted wavelengths.
A blue LED was determined to be the simplest option as it was readily available with its wavelength range being between 450 and 490nm. To further develop the prototype, at least one optical filter would be added in front of the light sensor to block out the light coming from the LED and only measure the light emitted by the fluorophore. Additionally, the blue LED could be replaced by a more precise wavelength LED or even a laser with collimating lenses to align the light rays right onto the sample.
Portability
The device was designed with portability in mind, since the bulky size is one of the drawbacks of the current federally approved drug testing device (Dräger DrugTest 5000) in Canada. To achieve this, our device is battery-powered, has a small OLED screen to display results, and connects wirelessly to a computer using Bluetooth technology.
Casing
3D modelling was done using Solidworks, then the designs were exported as STL files to be 3D printed on the Ultimaker 3D printers at SparQ studios on Queen’s campus. The first iteration was designed for with the breadboard circuit, as the electronic circuit had not been finalized at the time. This iteration was used as an introduction to 3D printing to members on the team who had no experience with it. The CAD model ended up being too large for the printer beds however, and single parts had to be printed in pieces and put together using glue. Evidently this was not ideal, and modifications were made for the next iteration.
Iteration 2 - Change Log
- Updated overall shape to fit 1st iteration of the printed circuit board
- Added improvements to the waste containment cartridge
- Stabilized top pipe fittings
- Fixed length of joint connections between top and bottom parts
Iteration 3 - Change Log
- Updated placeholder for 2nd rendition of the printed circuit board
- Added small holders for tubing
- Made section with waste container more stable and better fitting
- Added space to fit the 9V battery
Iteration 4 - Change Log
- Colour matching
- Increased size of tubing holders
- Standoffs for the printed circuit board raised
Fluid Distribution
The fluid distribution system consists of a way to get the antibody solution as well as the wash to the sample membrane and out to the waste container in an effective manner. The physical prototype utilizes a pressure-based system to push the liquid out of a syringe into some tubing that leads to the membrane.
To further develop the system, an attempt would be made to make microfluidic chambers for the antibody solution and the wash, using capillary action to drive the fluids towards the membrane. This system would have to make use of some sort of valves to control the flow. Various options were considered in the brainstorming phase of the project, including solenoid valves, duckbill valves, and cross-slit valves.
