Amazing stuff!
"... Every solid exhibits some amount of electric response to being bent or deformed, called flexoelectricity. Most of these responses are far too weak to exploit ...
But when researchers turned to ice, a prevalent solid on Earth and one of the most common solids in space, the story was different.
Adding table salt (NaCl) created a solid where every ice particle was surrounded by a few nanometers of briny liquid. When the salty ice was bent and unbent, this fluid sloshed back and forth, creating a current of ions that conferred a flexoelectrical effect around 1000 times larger than that of pure ice and on par with specially designed materials.
Salty ice has plenty of advantages in the real world, such as being
moldable (just think of fun-shaped ice trays),
non-toxic, and
requiring no trace elements, as found in typical electronics.
The simple solid could be incorporated into engineering projects in polar areas where sunlight is too low for solar power and water threatens soft robotics’ wiring and batteries, though it’s not a great candidate for deep space applications since the key briny liquid freezes at -70ºC. ..."
"... discovered that, despite not being piezoelectric, ice can generate electricity when unevenly deformed, thanks to a phenomenon known as flexoelectricity.
Building on this first discovery, the researchers have now achieved a new breakthrough: adding salt to ice significantly enhances its ability to generate electricity, opening up a wide range of potential technological applications. ..."
From the abstract:
"Despite 10% of the Earth’s surface being covered by ice, ice power remains untapped.
Although ice is known to generate electricity upon bending via flexoelectricity, the generated electric polarization per curvature, that is, the flexoelectric coefficient, is too small (~1–10 nC m−1) to be utilized for electromechanical devices.
Here we demonstrate that doping ice with NaCl can enhance its flexoelectric coefficient 1,000-fold, to ~1–10 μC m−1. We find that this enhancement is due to the bending-induced streaming current along ice grain boundaries.
On the basis of this mechanism, we fabricated flexural devices with an effective piezoelectric coefficient of ~4,000 pC N−1, which is comparable to that of the best piezoelectric materials.
The high flexoelectricity of saline ice brings the vision of harnessing ice power one step closer to reality, and may also be relevant to the electrical activity of ice-covered terrestrial regions and icy ocean worlds such as Europa or Enceladus.
In addition, the model for coupling between strain gradients and streaming currents is not limited to ice and provides a general framework for extracting electromechanical activity from liquid-infused porous solids."
Salty Ice: a New Way to Generate Electricity in Extreme Conditions (original news release)
Streaming flexoelectricity in saline ice (no public access)
Bending polycrystalline salty ice drives the flow of ions from one side to the other through small channels, generating an electrical current.
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