Showing posts with label mechanical resonators. Show all posts
Showing posts with label mechanical resonators. Show all posts
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Thesis on-line

For anyone interested my humble thesis in now available online on Tesis Doctorals en Xarxa

I am not particularly proud of it, I'm sure there are various things that could have been done better, but i hope this may help some of you. At least to know which mistakes to avoid! :)
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The high frequency resonator finally published!

figureThe good news from last week: the resonator paper is now available online here !


In the paper we measure vibrations of  a very short nanontube, which oscillates with very high frequency - up to 4.2 GHz! That's one of the highest frequencies up to now.


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A bit more about CNT resonators...

Here I show you the image of a high-frequency CNT resonator. It's a suspended SWNT of 100nm length and 4nm diameter.




Now the explication :)
It operates in transistor geometry, as shown below. Source-drain is where the AC current flows, inducing vibrations and with changing voltage on the gate we can change nanotube mechanical tension.
And yes - the actual resonator is the ultra-short carbon nanotube! It's so tiny that it's difficult to image it in SEM. But because it's so small it's easy to achieve high frequency operation!



The details of the high frequency devices will be published in Applied Physics Letters SOON!!! But I'll also try to explain it here in an easier way!
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Carbon nanotube resonators

During this year I worked a on mechanical resonators made of carbon nanotubes.

In general we have two types of carbon nanotubes (CNTs): single-walled (SWNT) and multi-walled (MWNT).  I also put the pictures, for those  who never got the chance to see them before. As the name suggests they are simply very little tubes, but their big advantage for mechanics and electronics is that they are very robust (the most robust material on earth, in fact!) and electrically conductive.



If you want to think of nanotubes for electrical applications, you can consider them as a small cables for nano or micro electrical circuits (easy, they in fact look like small cables) or semiconducting parts of transistor (a bit more difficult).


If you want to think how to apply nanotube mechanical properties, it`s maybe a bit more difficult. One single nanotube is normally too small to be of any use for our world, but is you use big amount of nanotube you can use it to reinforce materials, such as polymers.


Now the last part, think of putting together mechanical and electrical properties of CNTs. One of the options is inducing vibrations of a nanotube (just as you make a guitar string vibrate), but not with mechanical force, but with electric field. (That was exactly the subject of my talk from the previous post!)


Apparently, those little vibrating systems present various interesting properties, quite different from macro-scale. Also resonators made of SWNTs are quite different of those ones made from MWNTs. They can have very good perspective for giga-hertz (GHz) frequency processing and mass sensing.