Why do we need a fluorometer?
To ensure our methane monooxygenase (MMO) is effectively turning methane into methanol, both in the lab and in a real-world setting, we needed a way to track the amount of methanol being produced in our wastewater samples. Our method for tracking the conversion of methane into methanol relies upon another compound called coumarin. When coumarin is exposed to our MMO, a product called 7-hydroxycoumarin is formed, and this product can be easily measured using a fluorometer. Because of this, we sought to design our own fluorometer that was specialized to function in the specific wavelengths that we required to measure 7-hydroxycoumarin.
Parameters of our design.
When designing a fluorometer, there are a few key parameters that you must consider. First and foremost, you must ensure that you choose the correct excitation wavelength for the sample you are measuring. Choosing the correct optical filters is also very important to isolate the emission wavelengths from the sample that you want to measure. When using the fluorometer in our lab during our MMO testing, we also encountered issues with the plastic cuvettes that held our samples emitting interfering wavelengths, so the choice of cuvette material also had to be taken into account. Finally, the fluorometer had to be user-friendly for both lab and field conditions.
Purchased parts:
Our Fluorometer had several parts that we planned to purchase, those being:
-UltraViolet Filter Sheets ($26 for a 20”x24” sheet)
-Photo-Resistors ($6 for 30)
-340nm LED bulbs (around $200 each)
-Quartz Cuvettes (30$ for 2)
The most expensive material would have been the LED bulbs, costing around $200 per bulb.
Initial 3-D model:
Our initial 3-D model had a simple rectangular design and an emphasis on easy use in a lab setting. It houses the 340 nm LED on one side of the glass cuvette, and the Photo-resistor on the other. There is also a slot on the Photo-Resistor side that is used for mounting the ultraviolet filtering sheet. Finally, there is an open section of dedicated space for the Arduino. The theoretical procedure for using this design would have been to fill the cuvette with a sample, place it within the slot in the fluorometer, place the lid on top to prevent outside light from interfering with results, and then turn it on to activate the LED and Arduino to take measurements from the photo-resistor.
Updated 3-D model:
While our initial 3-D model was theoretically usable in a lab setting, requiring manual transfer of samples was unrealistic for field use of the fluorometer. To remedy this, we created a new design that features a pump system that can automatically swap liquid samples from a reservoir. The pump system is denoted by cubes in our 3-D model. The pump would transfer a small amount of sample liquid from a reaction tank into the cuvette through the top pipe, and then back into the reaction tank from the bottom. This new design also features an L shape which is intended to decrease the chance of light produced by our LED from reaching our photo-resistor. The automatic nature of this design would allow for intermittent testing of methanol levels in the reaction tank, which would provide valuable information on reactor efficiency over time.
First model
Second model