Friday, September 16, 2011

Work Experience and Liquid Crystals

Here's another guest blog from our work experience students. 15 and 16 year-old , Simrit Gill and Rahul Shiveram from Thornden School visited us in October. They got up to a number of activities, but two experiences really impressed them; Sadie Jones took them for a journey across the Galaxy in the Astrodome, and PhD student Mark Herrington showed them his Photonics lab: - this is what they reported ...

“Work experience” often has some mixed connotations; people may find themselves doing anything - perhaps stacking dusty shelves in an insignificant corner of a local grocery store, however, we found ourselves at the University of Southampton.

One might wonder what two GCSE students could do at a prestigious University, however it soon became apparent that there was actually quite a lot we could get up to. We encountered many interesting and mind-blowing research areas in Physics and Astronomy and visited many labs. These experiences included being immersed a film in the Astrodome, exploring labs where researchers are trying to find new and efficient ways to run the internet and a lab where their mission is to find a way to make lasers more powerful.

Our science classes have always taught us that there are 3 states of matter: Solids, Liquids and Gases. However, it's not quite that simple - according to the liquid crystal lab at The University of Southampton there are about five times that number! [Although there are 10 or 15 different liquid crystal phases we would call each of these a different mesophase and in terms of states of matter say that there are 5- Solid, liquid crystal, liquid, gas and plasma. According to Mark shown below - Ed.]

Liquid Crystals are an odd phenomena that most people associate with their flat screen TVs at home, unsurprisingly, they have many more uses. In the lab we were shown around, they were being used as a kind of ‘valve’ which could control the flow of light by electrifying a plate filled with a well known liquid crystal dubbed as ‘E7’. The way the ‘valve’ works is, well, complicated…but here goes.

The system starts off with unpolarised light which is made up of light travelling in all sorts of orientations. The laser is shone through a polariser, (similar to the 3D glasses used in the cinema), which filters out one orientation of light. The beam then travels through a liquid crystal which has its molecules lined up in the same orientation as the polariser. So, as you can imagine, the light travels straight through with ease. However, if you wish to shut the valve ‘off’ which involves running an electric current through the liquid crystal, which switches the orientation of the molecules by 90 degrees. Then it works like a venetian blinds and blocks off the light.

You must be wondering why blocking light out electrically could be useful, surely you could use a piece of black card? In fact, this mechanism would be extremely useful when switching something on and off rapidly for use in an optical computer (a computer using light signals instead of electrical signals as the method of transmitting information). We got to watch/partake in was the fabrication of the liquid crystal cell itself.


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