This week, we completed testing of our design. 

First, we tried out our machine with coloured water. We found that the colour intensity appeared to decrease consistently with each round of dilution. 

However, to quantify the performance and accuracy of our automated serial dilution system, we implemented pH measurement as our primary quantification method. Initially, we considered using hydrochloric acid as the acidic component; however, logistical challenges with lab scheduling and the handling of hazardous materials led us to choose a safer, more accessible alternative: lemon water, which contains citric acid. This substitution allowed us to replicate the acidic properties required for dilution testing without compromising safety or convenience.

We began by measuring the pH of our lemon water stock solution using a calibrated pH meter, then proceeded to test the pH of each subsequent dilution created by the machine. The results revealed a clear and consistent trend: with each serial dilution, the pH increased gradually (pH 4.9, pH 5.5, pH 5.8, pH 6.1, pH 6.7, pH 6.9), reflecting the anticipated decrease in hydrogen ion concentration. This trend validated the machine’s precision, as each successive dilution reliably met the expected reduction in acidity. Overall, the results confirmed that our system effectively achieved accurate and consistent serial dilutions, underscoring its potential for precise, automated lab processes.

However, as we were testing multiple complete cycles of serial dilution, we found that towards the end, our pipette was having difficulties arriving at the exact location to pick up the next pipette tip. All other mechanisms were working unfailingly  except for this mechanism. 

We did some research and checked each of our components for wear and tear. We discovered that our Arduino was heating up quite a bit at the end cycle of our serial dilution, and causing our stepper motor driver to heat up with it. If the stepper motor driver overheats, it can lead to imprecise or inconsistent movements in the x, y, and z axes, affecting the accuracy and reliability of the system. This is because when they overheat, these drivers can lose their ability to deliver consistent power, which can result in skipped steps, stalling, or erratic motor behavior. As our pipette tip is small, picking up the pipette tip remains to be the most precise movement required. Thus, this stage was the stage that got compromised. 

However, even when this happened, we were still able to continue testing, by guiding the pipette manually to pick up the tip.