Sue Lee, Week #2, Journey to the Lab(s)

This week, I applied the techniques I’ve only read on paper to the real lab. I learned how to manually fabricate a template of block copolymers through thermal and solvent annealing. My grad student, Brian’s research actually intertwines electrical engineering and materials science. So the main lab he works in, which is shared by other materials science researchers, happens to be a good five minute walk from Dr. Berggren’s lab. My grad student tells me that because of all the snow during the long winters in Boston, most of the buildings of MIT are connected somehow - which means I could get from the electric engineering department to the materials science department without setting a foot outdoors.

We share the lab with people from another lab that also work on the research of block copolymer self assembly. Brian showed me where what was, and taught me how to create a block copolymer pattern. Firstly, I spin coated the sliced silicon wafer with the PDMS (polydimethylsiloxane) solvent (which could also be done with PMS solvent). The silicon wafer is a thin slice of silicon that acts as a base that attracts one molecule layer of PDMS or PMS solvent, which can create desired patterns. I actually made a mistake on the very first step and dropped the PDMS solvent on the wrong side of the wafer which wasn’t silicon. I was afraid I had messed everything up, but Brian told me that it was fine and that we could redo it on the other side by flipping the wafer over.

After spin coating, I thermally annealed the wafer by placing it in the oven and baking it at 170 degrees Celsius for approximately 10 hours.

 

Then, I washed the coated silicon wafer with toluene to get the excess PDMS off of it, so that only one molecule layer remained. Afterward, I brushed the wafer with a PDMS-PS solvent and spin coated it once again. The hydrophobic PDMS and the hydrophilic PS interact to create a BCP pattern on the wafer. I annealed the wafer once again, but this time via solvent annealing, since both the ovens were occupied by other lab members. I placed the wafer in a flat glassware with a solvent created by a 5:1 ratio of toluene and heptane, and waited again for about 5 hours. Next week I’ll be learning how to use the scanning electron microscope (SEM) to take pictures of the block copolymer patterns.

While I wasn't in the lab, I continued to modify my code to better resemble what an actual block copolymer pattern would look like. Instead of having top,left,bottom,right neighbors, the nearest neighbors would be topleft, topright, bottomleft, bottomright, to form diagonal relationships with one another. I created a while loop within an if loop to ensure that only elements in both odd row and even column OR even row and odd column were chosen. The problem was that now I couldn't simply use my intuition to determine whether the code was successful or not, since the resulting image of the array was not a simple all-black or all-white image. I am currently coming up with a solution to be able to determine whether my code was successful through a quantitative method, so that I could calculate the +1s and -1s in the resulting array.

I also had a meeting with Professor Berggren this week about progress on my project. I presented the data I collected and walked him through my code. He helped me understand that the Ising model didn't actually violate the second law of thermodynamics, as well as the concept of temperature decreasing in simulated annealing. Dr. Berggren mentioned that it would be incredibly difficult, but very helpful if I could figure out how to use image processing to convert an SEM image of block copolymer patterns into a string of binary code. He said that it wasn't a finite solution that he was looking for, but rather the process of learning and overcoming obstacles along the way. I hope to be able to tackle this topic and contribute my knowledge to the rest of the lab members.

I went to watch the Blue Man Group show on the weekend, an incredible mash of strobe lights, paint, rock, comedy, and toilet paper (which my brother was buried in at one point of the show). It was good to have a laugh at the sheer bizarreness of something, and it was definitely a great way to end the week.