By Andy Choi
Scientists belonging to the National Institute of Standards and Technology (NIST) have helped a large team of university researchers to integrate a highly efficient, novel piezoelectric material with a silicon microelectromechanical system (MEMS). The advancement may lead to considerable progress in energy harvesting, imaging and sensing.
When electricity is supplied to piezoelectric materials they expand, and when the materials are squeezed they generate an electric charge. Quartz, a piezoelectric material, utilizes this property to maintain time. The battery in the watch feeds electricity to a quartz piece, causing it to expand and also contract within a small chamber. This movement occurs at a specific frequency that gets converted into time. Piezoelectric materials are also being used in ultrasound and sonar systems.
Traditional piezoelectric materials are sufficient for most applications. Researchers have been trying to invent new materials that expand with more force and also produce more powerful signals. This can lead to the development of “energy harvesting” technologies, which would be able to convert mechanical motions and walking energy into electrical power.
Scientists at the University of Wisconsin-Madison led a large team of researchers from the Penn State University, the Cornell University, the University of Michigan, the University of California, Berkeley and the Argonne National Laboratory to develop the novel piezoelectric material. The material, PMN-PT, is a crystalline alloy of magnesium niobate, lead and lead titanate.
The team developed a method to integrate the material, PMN-PT, into small cantilevers located on a silicon base. The cantilevers look like diving-boards. Silicon base is a normal material that is used for MEMS construction. The team used a voltage of 3 V and demonstrated that the MEMS material could deliver over four times the normal movement and with more force. When compressed, PMN-PT generates a stronger electric charge.
Vladimir Aksyuk, a NIST researcher, made performance measures by building engineering models of the PMN-PT cantilevers and also compared the material’s performance to other silicon systems. He said that though silicon was good for such systems, they are passive and can move only if heated. He added that incorporating PMN-PT to MEMS will boost the efficiency and sensitivity of energy harvesters.