Researchers 3D Print Tunable Ferroelectric Metamaterials

Researchers from the University of Buffalo (UB) have developed a unique method for 3D printing ferroelectric materials, that is materials that can have their polarization switched through the use of electric fields. With results published in the paper “A 3D-printed molecular ferroelectric metamaterial” in the Proceedings of the National Academy of Sciences, the study yields interesting possibilities for metamaterials and electronic devices.

Before we can get into the paper itself, we’ll need a little background on ferroelectricity. Just as some materials are naturally ferromagnetic, exhibiting magnetic capabilities, other materials are ferroelectric, meaning that they exhibit electrical polarization. They are pyroelectric and piezoelectric. While most ferroelectric materials do not contain iron, despite the “ferro” prefix, the magnitude and direction of their electrical polarization can be changed in response to changes in temperature, pressure or electric fields. This makes them ideal for specific electronic or biomedical applications, such as random-access memory, ultrasound imaging, data storage, displays and more.

A 3D printed structure with ferroelectric properties. Image courtesy of PNAS.

In the UB study, the research team employs imidazolium perchlorate (ImClO4), “a transparent molecular ferroelectric with superior electromechanical coupling and reprogrammable stiffness.” Because the material is water-soluble and transparent, it lends itself to digital light processing (DLP) and stereolithography (SLA) 3D printing. The low diffraction index of the material makes it possible for UV light to penetrate the material without light scattering.

The team, therefore, mixed ImClO4 powder with UV-sensitive resin and a DLP 3D printer from Anycubic. Once a complex lattice structure was printed with the concoction, the part was dehydrated, allowing it to maintain its shape. Moreover, due to the “reprogrammable stiffness” properties of the material, the team was able to record the printed object perform self-healing of cracks by dissolving the damaged part in ImClO4 solution.

The researchers demonstrated that the ferroelectric properties of the printed material were close to those of nonprinted ImClO4, with polarization responding appropriately to an electric field and dielectric properties responding appropriately to changes in temperature. Moreover, the self-healing, 3D printed part was able to recover its ferroelectric properties compared to a ImClO4 part that was allowed to degrade.

Whereas manufacturing of parts with ferroelectric properties typically takes hours, the UB team was able to make parts in just minutes due to the speed of a continuous DLP process. Lead author Shenqiang Ren, PhD, professor in the Department of Mechanical and Aerospace Engineering at the UB School of Engineering and Applied Sciences, said of the study, “The sky is the limit when it comes to ferroelectric metamaterials.”

The study was partially funded by the U.S. Army Research Office (ARO), which sees potential applications for aircraft soundproofing, shock absorbers and elastic cloaks.

Evan Runnerstrom, PhD, program manager at ARO elaborated: “One of the reasons ARO is funding professor Ren’s project is that molecular ferroelectrics are amenable to bottom-up processing methods — like 3D printing — that would otherwise be challenging to use with traditional ceramic ferroelectrics. This paves the way for tunable metamaterials for vibration damping or reconfigurable electronics, which could allow future Army platforms to adapt to changing conditions.”

This is just one of the latest examples of metamaterials being developed with 3D printing. Some research is directed at soft robots that react to their environments. Others incorporate nanoscale geometries to impact the behavior of objects at the macroscale. All of the above may make 3D printing in the future virtually unrecognizable from how we understand it today.