In a paper titled “Printing ferromagnetic domains for untethered fast-transforming soft materials” published in Nature, the researchers report how they used an elastomer composite containing ferromagnetic microparticles to 3D-print specific mechanical shapes while controlling the magnetic orientation of the microparticles as they are printed layer by layer.
What they describe as the “3D printing of programmed ferromagnetic domains in soft materials” consists in applying a magnetic field to the dispensing nozzle while printing, which reorients the particles along the applied field, providing a distinct magnetic polarity to the printed material.
Then, when a uniform magnetic field is applied to such a soft 3D-printed shape with different magnetic domains distributed throughout its structure, the soft robot delivers non-linear mechanical responses, with unique deformation capabilities depending on its design. This is a huge improvement over uniform magnetic material structures only capable of elongating, shrinking, or bending on a whole.
To make the most of their new 3D magnetic programming technique, the researchers also developed a finite element analysis physical model able to predict how a printed structure with given magnetic domains will deform under a magnetic field. The model takes into account the soft compound’s elasticity, magnetic patterns throughout the structure, and the external magnetic field as it is applied (continuously, intermittently or with changes of polarity).
With this predictive model, engineers could design their own structures and domain patterns, validate them with the model, and print them to actuate various functions.
Through various 3D-printed shapes and experiments, the researchers were able to demonstrate reconfigurable soft electronics with an actuation speed and a power density orders of magnitude greater than existing 3D-printed active materials. Among their findings were structures with controlled auxetic behaviours, enabling a mechanical metamaterial to jump upon sudden expansion of its structure. Other designs included a soft robot that can crawl, roll, catch fast-moving objects and wrap itself around a small object to transport it rolling across a distance.
Biomedicine and implantable electronics are likely fields of applications, according to Xuanhe Zhao, the Noyce Career Development Professor in MIT’s Department of Mechanical Engineering and Department of Civil and Environmental Engineering who led this research.
Massachusetts Institute of Technology – www.mit.edu