Simulation Vs. The Real Thing
Initially, when we were figuring out ways to test our sensor, we figured that we could simulate sweat by diluting saline solution. We found the average salinity of sweat and knew the salinity of the solution, so we could create a solution that would mimic sweat. We were wrong. First of all, the chemical make up is not the same. As far as I’ve understood it, I think that means that not all salinity values are equal. On a lower level, that makes sense. Different chemicals will have different chemical properties. The thing keeping us back was the “bodily fluids are gross” factor. However, when we started seeing odd results with our saline solution, we came back to the drawing board. It seemed like the initial hope we had had (that sweat and insulin would produce different results) would not be supported. At the same time, we came back around to the idea of testing with actual sweat. It turned out that the real thing was different than the simulant. Honestly, that was something that we should have thought of at the beginning. That is drilled in as we learn the math for our various majors: you can run calculations, but you cannot account for every little possibility.
For the most part, sweat behaved very differently than our simulant. Not only was the conductivity different, but the values for different people varied a lot. For the most part, everyone had a very large voltage reading between the two electrodes that we used (I had a very low reading, but I’m thinking that was more due to volume or some other experimental error that we didn’t notice). The good news was that testing with actual sweat caused a larger discrepancy between ranges of voltage for insulin and sweat, so our thresholds became easier to determine. Long story short, we’ve relearned that you can’t beat real data from real people.
NG
BME Design 