Rotational 3D printing of active-passive filaments and lattices with programmable shape morphing

TL;DR

This paper presents a novel rotational multimaterial 3D printing method to create active-passive elastomeric filaments with programmable intrinsic curvature and twist, enabling complex shape morphing for adaptive structures.

Contribution

It introduces a filament-centric fabrication strategy that encodes curvature and twist during printing, allowing precise control of shape transformation in 3D printed lattices.

Findings

Controlled natural curvature and twist are achieved through material distribution and liquid crystal alignment.

Printed lattices exhibit reversible shape changes including contraction, expansion, and out-of-plane deformations.

Simulation models accurately predict the shape-morphing behavior of complex architected structures.

Abstract

Natural filaments, such as proteins, plant tendrils, octopus tentacles, and elephant trunks, can transform into arbitrary three-dimensional shapes that carry out vital functions. Their shape-morphing behavior arises from intricate patterning of active and passive regions, which are difficult to replicate in synthetic matter. Here, we introduce a filament-centric strategy for programmable shape morphing in which intrinsic curvature and twist are directly encoded within multimaterial elastomeric filaments during fabrication. By harnessing rotational multimaterial 3D printing (RM-3DP), we directly prescribe the filament's natural curvature--twist field $\mathbf{k}(s)$ through controlled material distribution and helical liquid crystal mesogen alignment. When heated above their nematic-to-isotropic transition temperature ($T_\mathrm{NI}$), the helically aligned LCE regions contract along their local director field, while passive regions remain essentially unchanged. This approach enables independent control of bending and torsion at every cross-section along the filament centerline: the principal natural curvatures of the filament along two orthogonal axes as well as the local twist. Next, we printed architected lattices composed of unit cells formed by sinusoidal filaments that either reversibly contract, expand, or exhibit out-of-plane deformations. Discrete elastic rod simulations of Janus filaments with different natural curvatures and twist, which are interconnected within the printed lattices, allow accurate prediction of their observed shape-morphing behavior. By integrating active-passive elastomers, additive manufacturing, and computational modeling, we have created shape-morphing matter with complex programmable responses for applications that rely on adaptive, robotic, or deployable architectures.