July 23, 2010

Lately Dr. Noe has been requesting that I write more about my project in my journal, since all my entries have been about the talks I've attended. I've been trying to avoid writting the same thing twice since I write everything in my notebook because it helps me think out my problems. But, for the sake of communication I'll write a little about the problems I've been experiencing and solving so far.

My biggest obsticle has been to find a function generator that could give me a sine or square wave that has an amplitude of 100V. The best I could find at Stony Brook was one that gave me a nice 35V wave, but when running the experiments I quickly learned that it's not enough. 35V just simply won't drive my monomer to my glass plates. At some point Dr. Noe suggested I look up some circuits on how to build one and pointed me to one a previous student built. The student built one seemed to have bkoken connections and several people attempted to help me understand it, but everyone I talked to understood the general idea, but couldn't help me with the specific collection of boxes I was looking at. So after spending a day on that, I decided to try Dr. Metcalf's suggestion to build a Wein Bridge. This is something I've done before in an electronics class, so I looked up my old lab manual online and tried to recreate the circuit. Jacob helped me, but we couldn't find exactly the components specified in the manual. We tried to substitute other components, but at the end of the day the circuit wasn't working and another day had been wasted. So the next day I decided to take the path of least time since there was less than three weeks left in the REU program and my project still wasn't actually started. The solution was actually suggested a long time ago from Dr.Noe, which was to just utilize the fact that the AC out of a wall socket gives a voltage way above 100V, although not the frequency I am looking for. Still, I tried it, and it seems to work just fine. Therefore, last week I started doing my first actual experiments.

In my first experiments I tried making a grating on my UV light sensative cells with the black light that was originally used for the glow-in-the-dark stars project. I put a piece of plastic with a gratting printed on it on top of my sample and illuminated the cell. After doing this many times I found an illumination time that seemed to give the best quality lines of polymerized material. However, I used up all of my UV sensative cells doing this and am now waiting for more to arrive on Monday.

In the meanwhile I've been again attempting to build the Mach-Zender interferometer using the 404 nm diode laser. My big issues are lack of optical equipment such as stands and mirrors and beamsplitters inteded for compatability with my wavelength. I spent a lot of time on Friday trying to find stands for my beamsplitters. Believe it or not, but with five REU projects running at the same time, there is very little equipment left.

The last bit of Friday was also spent testing the same methods on the 400nm sensative cells with the 404nm laser. I hypothesized that the intensity of that diode laser, although nearly 10, 000 times less than what I know works, is still enough because when I was running tests wtih an inappropriate voltage, I was getting the same results with the small diode laser as the big 457nm laser I later switched to in order to rule out intensity as my problem. The result of my experiment is unlike what I've seen before. Mainly, the spot I illuminated doesn't look different from my results before I tried a higher voltage, but the surrounding areas, when I apply a voltage again, have a texture I've decided to call "rhino skin" because that's what it reminds me of. I don't know what this means and on Monday I will likely open up a brand new cell and try the experiment again with the 404nm laser and the 457nm laser and compare the results. The experiments seem to work best if I work with a brand new cell every time, but that's not an option since I only have a handful of them to begin with.

Meanwhile, I have to start writting my paper. Dr. Metcalf has mentioned a possible conference the REU students could attend, and I'm very interested in that.

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