Ions on the soles of your shoes

The RPI team developed a polymer film infused with a special chalcogenide perovskite compound that produces electricity when squeezed or stressed

In a recent study published in the journal Nature Communications, the team from Rensselaer Polytechnic Institute developed a polymer film infused with a special chalcogenide perovskite compound that produces electricity when squeezed or stressed, a phenomenon known as the piezoelectric effect. While other piezoelectric materials currently exist, this is one of the few high-performing ones that does not contain lead, making it an excellent candidate for use in machines, infrastructure as well as bio-medical applications. 

“We are excited and encouraged by our findings and their potential to support the transition to green energy,” said Nikhil Koratkar, Ph.D., corresponding author of the study and the John A. Clark and Edward T. Crossan Professor in the Department of Mechanical, Aerospace, and Nuclear Engineering. “Lead is toxic and increasing being restricted and phased out of materials and devices. Our goal was to create a material that was lead-free and could be made inexpensively using elements commonly found in nature.” 

The energy harvesting film, which is only 0.3 millimeters thick, could be integrated into a wide variety of devices, machines, and structures, Koratkar explained. 

“Essentially, the material converts mechanical energy into electrical energy — the greater the applied pressure load and the greater the surface area over which the pressure is applied, the greater the effect,” Koratkar said. “For example, it could be used beneath highways to generate electricity when cars drive over them.  It could also be used in building materials, making electricity when buildings vibrate.”

The piezoelectric effect occurs in materials that lack structural symmetry. Under stress, piezoelectric materials deform in such a way that causes positive and negative ions within the material to separate. This “dipole moment,” as it is known scientifically, can be harnessed and turned into an electric current. In the chalcogenide perovskite material discovered by the RPI team, structural symmetry can be easily broken under stress leading to a pronounced piezoelectric response.