UV Sterilizer for food

In my first quarter as a graduate student, I was enrolled in an Engineering Entrepreneurship class as a part of my Master's degree. We were tasked with designing a product to address global warming. I decided to approach this by targeting food spoilage. The food industry accounts for a significant portion of GHG emissions; I wanted to figure out how to reduce the amount of food wasted in order to reduce food production, transportation, and disposal. A survey sent to friends, family, and classmates revealed that nearly 50% throw away food that has gone bad once a week. Over 80% of respondents said that they have thrown away food before even opening it because it was spoiled, and almost 85% responded that they avoid buying certain foods because they are worried they will spoil before they can finish eating them. I considered several ideas such as adding an air filter to the circulation system to extract mold spores, but realized that could burn out the motor faster, didn't address spores already on food, and would require maintenance and cleaning. Eventually I settled on using germicidal UV-C as it works on a variety of microorganisms that cause food spoilage and food-borne illnesses, works whether the microorganisms are airborne or on the surface of the food, requires little to no maintenance, and can be installed with minimal disruption to the operation of the refrigerator. I then researched exposure requirements to kill mold, E. coli, and salmonella, among others. I calculated the power requirements for each bulb assuming best and worst case scenarios for a 24 hour exposure. The next step was to compile a BOM and estimate the cost of each unit; this was important for the minimum viable audience calculations to determine if this could feasibly be a commercially viable product. I then found UV-C LEDs that met my requirements and designed custom circuit boards in EAGLE to support and power them; this required building a custom library in EAGLE from datasheets, as the components I wanted to use were not included with built in libraries. I then submitted RFQs to several PCB manufactures to compare their prices and turnaround times; the manufacture I ended up going with even offered a sponsorship program for boards used in academic projects. My sponsorship application was approved and I created a project page (linked below) for other users to view. I created several different logos in Adobe Illustrator and renders of the board using Solidworks PhotoView 360 to send out in a interest survey to get feedback on what people felt best represented the product and which they would be most likely to buy. While waiting for the boards to arrive, I ordered the components I would need, a few new tools, and reconfigured my workbench for assembling the demo unit. I built the switch module to have an RGB LED behind the logo to allow the customer to chose whichever color they preferred. The switch module turns all the UV-C LEDs off as soon as the door opens to reduce the risk of eye or skin irritation; the power of the LEDs was specifically chosen to be as low as possible so that accidental exposure wouldn't be dangerous. When the boards arrived, I taught myself how to use solder paste and an SMD reflow station to assemble boards; the LED is 1.3mm on each side and the connectors have a 1.2mm pitch, making these the smallest components I have ever soldered. I then set up a small photo studio on my workbench to take some product photos; I continue to be pleasantly surprised how versatile my workbench is. I edited the RAW photos in photoshop and made a sticker for the outside of the refrigerator. The last step was to add some clear nail polish to seal any exposed pads and then install the system in a mini-fridge to test it. I really enjoyed this project as I was able to pull in many different disciplines and skills that I have learned over the years. If I were to do this again, I would add a couple of test pads near the sloped region in the lower right to make it easier to test the connectors, check for shorts, and use alligator clips to power the LEDs during testing. These could then be sealed over with nail polish before being installed in the refrigerator.