Harvard develops 3D printing for programmable artificial muscles

Researchers from Harvard's School of Engineering and Applied Sciences and the Wyss Institute have designed a groundbreaking 3D printing technique that mimics natural structures to create artificial muscles. Inspired by spiral forms found in nature, like vines and elephant trunks, they achieved that synthetic soft materials can perform complex movements such as bending, twisting, and contracting in response to heat stimuli.

The key innovation lies in the rotational multimaterial 3D printing method, which differs from traditional linear processes. Using a rotating nozzle, this technology extrudes and combines two types of materials: an active one, a liquid crystal elastomer (LCE), which contracts when heated, and a passive, soft elastomer that remains inert. The internal helicoidal structure formed during extrusion resembles biological tissues.

When heat is applied, the liquid crystal elastomer contracts, creating tension against the passive elastomer, resulting in predictable movements like bending or twisting without additional mechanical assembly. The rotation speed of the nozzle during printing controls the final shape of the filament once activated, allowing for customized responses tailored to specific needs.

This development opens new avenues in soft robotics and biomedical devices, as these helicoidal filaments can be used to build complex, functional structures like temperature-responsive filters or gripping tools. The programmable architecture transforms simple filaments into sophisticated devices capable of precise movements based on their internal design.

The study, published in PNAS, emphasizes how collaboration between mechanics and molecular alignment experts validated material behavior through advanced techniques such as X-ray scattering, showcasing its potential for robotics and medical applications.