Smart Materials Used in Ultrasound Behave Similar to Water

A team of researchers is gaining new insight into the smart materials used in ultrasound technology. While forming the most thorough model to date of how these materials work, they have found striking similarities with the behavior of water.

The research, published in Nature, was led by Andrew M. Rappe, the Blanchard Professor of Chemistry and a professor of materials science and engineering in the School of Engineering and Applied Science, and postdoc Hiroyuki Takenaka in the Department of Chemistry. Penn Research Specialist Ilya Grinberg and alumnus Shi Liu also contributed to the study.

The researchers in this group are interested in how materials interact with, harness and convert energy into different forms. In this study, they were investigating a behavior of smart material called piezoelectricity, which is the interchange of mechanical energy with electrical energy.

In piezoelectricity, applying an electric field to a material reorients dipoles within it; this is the key to the functionality of the material.

“You can imagine that there's a cage of oxygen atoms,” Rappe says, “and there's a positive ion in the middle. If it sits in the middle of the cage then there's no dipole, but if it moves off-center then there's a dipole. The rearrangement of those dipoles is what leads to these smart material properties.”

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