Morgan
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Flexoelectricty
I was reviewing an article on bending a thin sheet of salt 90 degrees. In the past I had sawed a piece of Himalayan rock salt and noticed the sliver
strangely bowed as it was being cut.
Plasticity of Rock Salt Crystals
https://www.nature.com/articles/135310a0
My sliver
https://www.youtube.com/watch?v=sR-QHCIXQ98
And this tidbit
https://en.wikipedia.org/wiki/Halite#/media/File:Halite-Egyp...
And happened upon this ice flexing characteristic, maybe of interest.
Shocking Discovery That Water Ice Can Produce Electricity, Possibly Explaining Lightning
https://www.youtube.com/watch?v=upJxH1cTvVE
https://onlinelibrary.wiley.com/doi/10.1002/smll.202406726?m...
https://interestingengineering.com/energy/salty-ice-bending-...
[Edited on 19-10-2025 by Morgan]
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Admagistr
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This is a very interesting topic for me. I once read a testimony from a man who claimed that he broke ice blocks in the dark and that the blocks
glowed, which he explained as triboluminescence of ice. I searched for information on whether ice is triboluminescent and rarely found somewhere that
it is.
But I had my doubts about whether this was reliable information. Now I have an explanation. However, it is not enough to explain where lightning
comes from. There are many processes at play, but this is one of many processes that leads to the formation of lightning in a Cb cloud. Are you
planning to conduct a practical experiment where you can generate an electric charge from salt ice?
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Morgan
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I don't really know enough about it yet to try something or even if I would have the means but I found a few more tidbits.
"by adding common salt (NaCl) at a concentration of 25%, ice exhibits a flexoelectric coefficient 1,000 times higher than that of pure ice. In other
words, its ability to generate electric charge is increased by a factor of 1,000, bringing it to the level of some piezoelectric materials currently
used in electronics."
"This phenomenon is explained by the flow of salty water along grain boundaries within the ice. When the material is bent, the water molecules and
salt ions trapped between the ice crystals move from the compressed regions to the stretched regions. This movement generates an electric current,
contributing to an enhanced flexoelectric response of the ice."
https://www.nanowerk.com/news2/green/newsid=67634.php
Somehow, I opened a link entitled Streaming Flexoelectricity in Saline Ice and where it describes Methods and Preparation of Samples below the full
article. "Online access to this article has been provided by Springer Nature Sharedit"
Now it won't let me open it but it has more information. A simple video would be nice to see if someone could construct one.
X. Wen et al. Streaming flexoelectricity in saline ice. Nature Materials. Published online September 15, 2025. doi: 10.1038/s41563-025-02332-5.
[Edited on 20-10-2025 by Morgan]
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Admagistr
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Thanks for the information,Morgan! It occurred to me that other alkaline chlorides might produce even better results than NaCl, but I have no evidence
to support this; it's just my speculation. It would have to be tried. LiCl,KCl,RbCl, and CsCl would be worth trying.
[Edited on 20-10-2025 by Admagistr]
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Morgan
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"This phenomenon is explained by the flow of salty water along grain boundaries within the ice. When the material is bent, the water molecules and
salt ions trapped between the ice crystals move from the compressed regions to the stretched regions. This movement generates an electric current,
contributing to an enhanced flexoelectric response of the ice." Also, in the Streaming Flexoelectric methods article I couldn't get the link to work,
they refer to the 2 mm thick sheet of saline ice sandwiched between two pieces of aluminum foil as an ice capacitor. "Such a streaming current can
also be generated in a bent polycrystalline saline ice where opposite signs of stress on the beam surfaces squeeze the liquid from one side to the
other."
As an aside/tangent, maybe of interest, diffusion of a salt solution through a porous material.
"The electrostatic energy increases as the salt concentration of the solution is reduced due to diffusion."
Extracting Renewable Energy from a Salinity Difference Using a Capacitor
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.10...
[Edited on 21-10-2025 by Morgan]
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Morgan
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Another niche approach, I guess.
The giant flexoelectric effect in a luffa plant-based sponge for green devices and energy harvesters
"Therefore, a chemical treatment was performed to remove the lignin and hemicellulose from the natural dry LS, and the detailed treatment procedure
can be found in Materials and Methods—Luffa sample treatment and briefly summarized in Fig. 2. As shown in Fig. 2B, the dry LS, as bought, possesses
a natural three-dimensional porous interconnected network structure. The treatment successfully removes the majority of hemicelluloses and lignin
leaving behind mainly the type-I cellulose crystal form characterized by FT-IR (Fourier-transform infrared spectroscopy) spectra and X-ray diffraction
as shown in SI Appendix, Fig. S2."
https://www.pnas.org/doi/10.1073/pnas.2311755120
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Rainwater
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Get one of these https://www.homesciencetools.com/product/galvanometer/ and hook it to a sheet of aluminum foil and a hammer. You will need to run a few
calibration swings as contact between the aluminum and steel if your hammer should produce some movement due to crystal strain and galvanic reactions.
"You can't do that" - challenge accepted
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Morgan
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It doesn't seem like any big sparks are going to be made with flexoelectric materials but maybe some specialized applications will come about.
"The flexoelectric effect is generally weak at the macroscale, which is an impediment to its wide applications."
https://www.pnas.org/doi/10.1073/pnas.2311755120
On a small scale, I noticed two very tiny/meager sparks seen at the 10 and 24 second mark at the flat surface of where this hot brass fitting makes
contact with the salt in the clip below. It's barely noticeable and I only noticed the second spark at the 24 second mark today. I wonder if it might
be a kind of "thermo-flexoelectric effect" where instead of a bending, heat transfer is distorting/flexing the salt molecules to make a flash? It
seems if bending creates a flexoelectric effect, the expansion and contraction of salt as it's heated is a kind of flexing. Or maybe a triboelectric
effect or the sudden fracture of a tiny crystal occurred.
When the physicist John Tyndall was studying the Trevelyan Rocker effect, of all the minerals he experimented with, he found Rock Salt to be the best.
"I scarcely know a substance, metallic or non-metallic, with which vibrations can be obtained with greater ease and certainty than with this mineral."
(At the 10 and 24 second mark tiny sparks)
Quick Disconnect Brass Fitting as a Simple Trevelyan Rocker Using Salt
https://www.youtube.com/watch?v=i-7kbkVx8bI
I never noticed any other sparks when experimenting with salt, but the resonant expansion and contraction is interesting to play with, thinking some
other idea might come about.
This heavy brick rocking on its side here will also rock nicely when stood on end and being more unstable, can topple over as feedback builds.
Himalayan Rock Salt Brick Motion from Heat
https://www.youtube.com/watch?v=vGpQsdCtyj8
Heating Halite to Create Sound
https://www.youtube.com/watch?v=A1MamnU3fYg
I liked this triboelectric effect for making sparks.
"I have measured voltage as high as 250kV with a short circuit current (to ground) of as high as 20µA on the forward stroke of the pipe through the
sleeve. The sparks are not quite as bright as they appear in the pictures, but they are nevertheless quite impressive to the uninitiated in
electrostatics, not to mention being quite loud. These sparks are 5 1/2 inches (14cm) long, but under optimum conditions I have made sparks as long as
seven inches (18cm). I think with a little tweaking of the configuration, they might be much longer."
http://amasci.com/static/foster1.html
https://www.pulse-jets.com/phpbb3/download/file.php?id=14230...
https://www.pulse-jets.com/phpbb3/download/file.php?id=14229...
https://www.youtube.com/watch?v=KMQYp218a-Q
A good electrostatic page
Antonio Queiroz
https://www.youtube.com/@acmdq2007
https://www.coe.ufrj.br/~acmq/electrostatic.html
[Edited on 23-10-2025 by Morgan]
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