Bioinspired artificial muscle filaments bend and twist with temperature changes

Rotational multimaterial 3D printing

Because the active liquid crystal elastomer shrinks along its internal molecular alignment direction when heated, and the passive material does not, even a simple bilayer filament bends as one side shortens and the other resists. Rotating the nozzle as it prints effectively "writes" a helical alignment of the active molecules into the filament.

To validate and predict the materials' behavior, the team worked closely with Professor L. Mahadevan, whose group specializes in the mechanics of natural structures, and Professor Joanna Aizenberg, whose lab helped characterize the molecular alignment of the liquid crystal elastomers using X‑ray scattering measurements performed at Brookhaven National Laboratory.

Demonstrations of complex structures

Once the researchers could provably program the shape change of a single filament, they used those filaments as building blocks for more complex, architected structures.

In one experiment, a lattice printed with alternating expanding and contracting regions morphed into a dome‑like shape when heated in an oil bath, closely matching the form predicted by simulations.

The team is exploring scaling the technology. With custom‑fabricated nozzles and carefully tuned inks, they have already printed filaments as small as roughly 100 microns in diameter and see opportunities to go smaller.

Jackson Wilt, graduate student and co-authorIn terms of scalability, you could create more complex nozzles that integrate with other materials in the future – like, having a liquid metal channel to enable actuation, or integrating other functionality."

Source:

Harvard John A. Paulson School of Engineering and Applied Sciences

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