3D printing has been used for creating scaffold structures to enable the creation of ferroelectric metamaterials.
Ferroelectricity relates to crystalline substances that have spontaneous electric polarization which can be reversed by an electric field. Ferroelectric materials have applications in electronic components, computer memory, mechanical devices and even as a catalyst in chemical processes.
You can see the piece that was fabricated with the aid of AM in the image below.
Creating these metamaterials has been largely uneconomical until now, as they are traditionally made of ceramics. But a team of researchers from University at Buffalo (New York), with some funding from the U.S. Army Research Office, have made steps into making their creation more cost effective, and they used 3D printing to do just that.
The research team devised a plan to 3D print a scaffold-supported ferroelectric crystalline lattice made of imidazolium perchlorate.
The process is highly tunable and so can produce metamaterials with varying stiffness, which has applications in vibration dampening and also in acoustics. It is effectively a stimuli-responsive material, and is therefore programmable in terms of stiffness, which can be tuned on demand during application.
“A molecular ferroelectric architecture with resonant inclusions then exhibits adaptive mitigation of incident vibroacoustic dynamic loads via an electrically tunable subwavelength-frequency band gap.”
One area of research could yield new methods for producing acoustic blankets for aircraft soundproofing.
imidazolium perchlorate (ImClO4) is water soluble, and so the molecular ferroelectric ImClO4 crystal is mixed with photopolymerizable material to achieve a transparent printable precursor ink solution.
It is then printed with the SLA method, producing a solidified (yet porous) scaffold of crystal precursor material.
The scaffold is then dehydrated under an electric field to crystallize ImClO4 with the desired polarization orientation. The porosity provides a carrier for the in-situ crystallization of the ferroelectric molecules in the precursor mix.
In a way, it could be thought of as the chemical equivalent of baking the stucco on in an investment casting process. The electric field crystalizes the structure of the scaffold just like heat would solidify the stucco. Both provide a copy of the original geometry.
“One of the reasons ARO is funding [this] 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,” said Evan Runnerstrom, program manager at the Army Research Office.
“This paves the way for tunable metamaterials for vibration damping or reconfigurable electronics, which could allow future Army platforms to adapt to changing conditions.”
The research paper also reveals that the metamaterial has shown self-healing ability in addition to its use as a tunable-frequency vibration-isolating architecture.