Thursday, May 14, 2015

How doctor blading ruined everything

During the very first lecture of 20.109, Angela Belcher talked about the solar cell module, and how she would give the team with the highest efficiency a special prize. Krystal and I had chosen each other to be partners, and though we hadn’t yet formed a special 20.109-partner-bond at this point, we looked at each other and nodded—WE WERE GOING TO WIN.

As we progressed through 20.109, Krystal and I dominated the efficiency game during lab days: pipettes were set to the correct volumes while our samples were in the centrifuge, and we read ahead through all the procedures during incubation times to eliminate any wasted time. Sometimes, we had our off-days, but most of the time we finished first. It wasn’t a competition against the other teams, but rather, a competition against ourselves to compact all of our lab work into the shortest possible amount of time. Usually, we were motivated by the fact that the sooner we finished, the sooner we could eat food.

For some of the experiments prior to Module 3, we produced some questionable data, but we always reassured each other that we weren’t competing for a prize, so it was okay. Module 3 came along, and, mentally, we were more prepared than ever to win.

During the first few lab days of Module 3, everything seemed to be according to plan. We followed the procedures carefully, and double-checked all of our calculations. Then, came the doctor-blading day. “You’re going to have to do this,” Krystal implored to me. “My hands are too shaky. You have to carry us.” (Or she said something like that to me).

I practiced on the glass coverslips with the glue and tape, and after a few tries, I deemed myself ready. Off we went to the Koch, and we were presented with the materials that would eventually form our solar cell. THIS WAS IT.

The paste was in a little glass jar with a bent pipette tip to “scoop” out the paste. Krystal used the tip to apply some paste next to the square region, and I carefully attempted to doctor-blade the cell using the same technique as with the glue. As I scraped the paste across the slide, however, I came to a dark realization—there wasn’t enough paste. Frantically, Krystal and I tried to scoop more paste near the square to recover from what we thought was a minor mishap.

But alas, the paste did not seem to be scoop-able with the bent pipette tip, and we became so frustrated with the paste that we were virtually stabbing our little solar cell square with the pipette tip to try and transfer the paste to the slide. Eventually, Krystal got the brilliant idea to unbend the pipette tip, with which we were finally able to get the paste onto the slide. But it was too late. Centuries seemed to have already passed since our first attempt at doctor-blading the paste, and so at this point, our little square of paste was not only unreasonably thick, but also terribly bumpy.

The next lab day, we looked at our cell under the microscope and the cell looked like a county map with the different counties separated by nice, wide rivers. Everything was ruined. We held out hope that perhaps this would somehow still result in the highest solar cell efficiency in the class, but it did not. We were third to last with an efficiency of 0.39%. Who knew that this one day would be so important in determining our fate for winning the prize. But alas, now we know that, in the future, if we were to ever compete for a prize for most efficient solar cell, we should doctor-blade our cell correctly. 

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