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LLNL Researchers Debut New Class of 3D-Printed Metamaterials

“Field-responsive mechanical metamaterials” change properties under magnetic fields.

Researchers injected a magnetorheological (MR) fluid into hollow lattice structures built on LLNL’s Large Area Projection Microstereolithography (LAPµSL) platform, which 3D prints objects with microscale features over wide areas using light and a photosensitive polymer resin. Photo by Julie Mancini/LLNL

A new class of Lab-developed “field-responsive mechanical metamaterials” (FRMMs) employ a viscous, magnetically responsive fluid that is manually injected into the hollow struts and beams of 3D-printed lattices. The fluid’s ferromagnetic particles located in the core of the beams form chains in response to the magnetic field, which rapidly stiffens the fluid and the lattice structure. Photo by Julie Mancini/LLNL

Researchers at Lawrence Livermore National Laboratory (LLNL) have developed a new class of metamaterials that can almost instantly respond and stiffen 3D-printed structures when exposed to a magnetic field. The development has huge implications for next-generation helmets, wearable armor and countless other innovations.

These new “field-responsive mechanical metamaterials” (FRMMs) use a vicious, magnetically responsive fluid that is manually injected into the hollow struts and beams of 3D-printed lattices. Unlike other shape-morphing materials, the structure of the FRMMs does not change.

The fluid’s ferromagnetic particles located in the core of the beams form chains in response to the magnetic field, which stiffens the fluid and the lattice structure as a result. This response happens instantaneously—in less than a second. The change is easily reversible and highly tunable by varying the strength of the applied magnetic field.

“What’s really important is it’s not just an on and off response; by adjusting the magnetic field strength applied we can get a wide range of mechanical properties,” says lead author Julie (Jackson) Mancini, an LLNL engineer who has worked on the project since 2014. “The idea of on-the-fly, remote tunability opens the door to a lot of applications.”

Mancini says the technology could be useful for impact absorption—for example, automotive seats could have fluid-responsive metamaterials integrated inside along with sensors to detect a crash, and seats would stiffen on impact, potentially reducing passenger motion that can cause whiplash. It also could be applied to next-generation helmets or neck braces, housing for optical components and soft robotics, among many other applications.

The research appears on the cover of the December issue of Science Advances, a peer-reviewed multidisciplinary open-access scientific journal, published online.