Piezoelectric materials come in only a few defined shapes and are made of crystal and ceramic that often require a clean room to manufacture. While ceramics can be 3D printed, the team led by Xiaoyu 'Rayne' Zheng, assistant professor of mechanical engineering in the College of Engineering, and a member of the Macromolecules Innovation Institute, developed a model that allows them to manipulate and design arbitrary piezoelectric constants, resulting in the material generating electric charge movement in response to incoming forces and vibrations from any direction, via a set of 3D printable topologies.
Unlike conventional piezoelectrics where electric charge movements are prescribed by the intrinsic crystals, the new method allows users to prescribe and program voltage responses to be magnified, reversed or suppressed in any direction.
"We have developed a design method and printing platform to freely design the sensitivity and operational modes of piezoelectric materials," said Zheng. "By programming the 3D active topology, you can achieve pretty much any combination of piezoelectric coefficients within a material, and use them as transducers and sensors that are not only flexible and strong, but also respond to pressure, vibrations and impacts via electric signals that tell the location, magnitude and direction of the impacts within any location of these materials."
His team produced a substitute material that mimics a piezoelectric crystal but allows for the lattice orientation to be altered by design. "We have synthesized a class of highly sensitive piezoelectric inks that can be sculpted into complex three-dimensional features with ultraviolet light. The inks contain highly concentrated piezoelectric nanocrystals bonded with UV-sensitive gels, which form a solution - a milky mixture like melted crystal - that we print with a high-resolution digital light 3D printer," said Zheng.
The team demonstrated the 3D printed materials at a scale measuring fractions of the diameter of a human hair. "We can tailor the architecture to make them more flexible and use them, for instance, as energy harvesting devices,