Friday, February 23, 2018

Time to catch up

I haven't posted in about a week, so this is to account both for this week (which was really one day because I was absent Wednesday) and last week. 

I been mostly looking at the optical properties of spider silk. As I discussed among the many applications of spider silk was the possibility of using it in place of fiber optic cable (FOC). At the time of my presentation, I had yet to learn more about it since I was looking in to other things. I have now been investigating this. What I have found so far is very promising. 

First let me explain the index of refraction. The index of refraction is defined as:

n ≡ c/v 

where n is the index, c is the speed of light in a vacuum, and v is the speed of light through a particular substance. The index of space is obviously 1, and air is very close to that. Normal FOC typically has an index of about 1.44 which is pretty good. There is only about a 31% decrease in the speed of light, which is still ridiculously fast. (~2.083X10⁸ m/s) 

Now, spider silk has been found to have an index of about 1.55. That's still good, but not as good as FOC. Spider silk reduces the speed of light by ~36%. So, between FOC and spider silk, there's only a 5% difference in speed. While it would take light traveling the distance to the moon 1.85 seconds through FOC, it would take 1.98 seconds through spider silk. So the question I have to answer now is: is it worth it to reduce the speed?

FOC typically has a diameter of 50 microns (50 millionths of a meter) not including the layers of insulation and protection around it. Spider silk has a diameter close to 7 microns. This means that you have more channels to transport information in the same space, ~7 times as much. 

Also I've considered too the production of FOC vs. silk in making it available for common and universal use. FOC can now be made at 50 m/s. Silk likely can't compete with that speed. At best, you can only produce a few meters per second. 

The process of manufacturing FOC is a very complex process that involves chemical vapor deposition, drawing, and coating. The manufacturing of spider silk is also complex, as discussed in my presentation. However, silk has no bi-products and the lab setup is simple.

FOC also has some practical issues. It's glass, so it's not nearly flexible as silk. It also has issues with installation because of its maximum tensile strength. 
 
Thinking holistically, you have to make the best use of time, resources, money, and space for this to be a feasible option. Spider silk as a product itself would reduce the normal speed by 5% and is manufactured at a slower rate. However, it is smaller in diameter, is cheaper to make, is clean, and more durable. 

Of course I may be biased because this is my thesis and I want silk to be used anywhere possible, but I think silk could be a viable alternative to fiber optic cable despite any cons. I will continue to investigate this one application as I move on to others. 

Next week, I'll look at applications based on its birefringence.

Birefringence is the property of a material where the index of refraction changes based on the polarization and propagation direction of light. Think liquid crystal displays in alarm clocks. The display changes as you angle it away or towards you. This property is made use of in numerous medical instruments etc. 

Should be interesting...

- Noah

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