Streaming flexoelectricity in saline ice

Area of Science:

• Materials Science
• Physics
• Geophysics

Background:

• Ice covers 10% of Earth's surface, yet its energy potential is largely untapped.
• Flexoelectricity in ice generates electricity upon bending, but the effect is too weak for practical applications.
• The flexoelectric coefficient of pure ice is approximately 1-10 nC/m.

Purpose of the Study:

• To investigate methods for enhancing the flexoelectric properties of ice.
• To explore the potential of saline ice for electromechanical energy harvesting.
• To develop a theoretical framework for electromechanical activity in porous solids.

Main Methods:

• Doping ice with sodium chloride (NaCl) to modify its flexoelectric properties.
• Measuring the flexoelectric coefficient of saline ice.
• Fabricating flexural devices utilizing saline ice.

Main Results:

• Doping ice with NaCl increased its flexoelectric coefficient by 1,000-fold, reaching ~1-10 μC/m.
• The enhancement is attributed to bending-induced streaming currents along ice grain boundaries.
• Fabricated devices demonstrated an effective piezoelectric coefficient of ~4,000 pC/N, comparable to leading piezoelectric materials.

Conclusions:

• Saline ice exhibits significantly enhanced flexoelectricity, making ice power a viable energy source.
• The findings have implications for energy harvesting, understanding planetary bodies like Europa and Enceladus, and developing general models for electromechanical activity.