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Introducing Flexoelectricity

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David Ashton
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Re: Flexoelectricity
David Ashton   9/10/2014 5:59:10 PM
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Many thanks Bernard.  Yeah, we don't let you get away with much around here :-)

ccorbj
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Re: Flexoelectricity
ccorbj   9/10/2014 10:22:00 AM
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Hi David - you guys are making me work for my living on this post. Good - I like a challenge! While there should be some FEE effect in any LCD distortion, it is probably far too small to be significant in this case. I have often wondered myself about this - it seems the reason is that when you press on the display, you change the concentration of liquid crystal where you are pressing, which changes the amount of optical rotation (from backlight) in that area. As the light then passes through a polarizer (3 if a color display), you get a variation in intensity which leads to the visible effect.

 

There is a fairly detailed discussion of the topic here:

http://chemistry.stackexchange.com/questions/6829/why-do-liquid-crystal-displays-lcds-visually-distort-under-pressure

 

Thanks for leading me to a better understanding of this

David Ashton
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Flexoelectricity
David Ashton   9/9/2014 7:24:29 PM
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Hi Bernard, thanks for an interesting article.

I have noticed that if you press on the screen of an LCD (for instance a multimeter multi-7-segment type) the segments will darken.  Is this becuase of flexoelectrity in the LCD or purely due to the mechanical movement of the liquid crystal?  You get a similar effect on computer or TV screens - if you tap your finger on one it looks like a drop of water falling into a pool. 

 

ccorbj
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Re: LCDs
ccorbj   9/9/2014 12:45:09 PM
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Interesting suggestion. I did some looking around and can't find anything published on that topic but for sure the effects of localized strain gradient (eg from an electron microscope probe on a film) have been considered. Again, early days, but thanks for the comment!

antedeluvian
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LCDs
antedeluvian   9/9/2014 11:13:46 AM
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Bernard

the effect has also been observed in liquid crystals, polymer films and bio-membranes

I realise that this is really early days, but I would think that this might have a bearing on touch screens down the road.

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