We’re done with 66.667% of the internship! While 5 significant figures may have been enough to get humans on the moon, I can’t decide if they are enough for this blog. Thankfully, though, our design decisions are not as vague to make. This week, we finalized the mechanical structure of our device.
Last week, I mentioned that we had finally decided on using a 55 gal. steel oil drum as the container of our device. The oil drum was chosen because of how readily accessible it is, especially in the low-resource settings that we are designing for. It has a standard cylindrical geometry that opens the door to some exciting design prospects. The steel is also an upgrade to plywood which, in addition to not being accessible, can also warp after repeated exposure to UV-C light. With the container selected, we began selection of framework designs for our mask holder.
We had two major designs. These included a pyramidal frame and a rectangular frame (see below). Both of these frames had their pros and cons. For the pyramid, you can fit more masks (27 including all sides!), as well as increase the sterilization efficiency more than 20-fold. However, this requires a large amount of stacked bulbs (8 in total), which increases overall manufacturing and power cost as well. At the same time, with its compact geometry, we would have to potentially attach a bulb to the lid, which adds a number of complex mechanical issues, especially with handling of delicate bulbs in high-stress environments.
For the rectangular frame idea, we would have three bulbs on either side of the frame. The bulbs would each be at a different height to ensure all levels of the mask-holder receive uniform UV exposure. The frame itself would be a matrix of masks with 3 rows (and 5 masks per row), increasing the sterilization efficiency more than 10x. Since we would be able to attach the UV tubes to the oil drum, this frame would give us higher mechanical stability (as well as use fewer bulbs!).
One thing I’ve learned to appreciate over the course of this internship is the value of breaking things down into simpler tasks. When we created our design criteria, we did so because of the design goals we hoped would shape our project. Now, after breaking down each aspect of each framework, we began to cycle through our criteria. After many rounds of discussion and deliberation, we decided to go with the rectangular frame owing to its comparative mechanical and usability advantages. In the end, what seemed like a complex issue (that would have shaped the rest of our project) ended up as a simple decision based on our fundamental goals.
As I move into the final stages of our design, I’m trying to make it a habit to trust the process. I continuously remind myself to look at our project from afar and see how every step we take, and every singular change we make affects the bigger picture. And it’s beautiful.