Multi-Material 3D Printing with a Twist

Twisted and helical architectures are ubiquitous in natural and engineered systems due to their unique mechanical behavior and multifunctionality. For example, nastic motion in plants arises from helically arranged fibers within plant cell walls, while human muscle contraction arises in part from the helical arrangement of actin and tropomyosin in skeletal muscle thin filaments. Emerging engineered materials, e.g., artificial muscles and structural composites, also benefit from their arrangement into twisted, coiled, and helical geometries. Twisted and helical synthetic architectures have been fabricated by self-assembly, microfluidics, and winding, twisting, and braiding of filaments. However, these methods are unable to simultaneously create and pattern helical filaments in two- and three- dimensional architectures. Here, we report a multi-material rotational 3D printing method that enables control over the local orientation of multiple materials within circumferentially heterogeneous filaments. Continuous rotation of the multi-material printhead during printing results in 1D filaments with a twisted architecture that exhibit unique properties, including structural filaments composed of stiff “springs” embedded within a compliant matrix as well as artificial muscles composed of helical dielectric elastomer actuators. Looking ahead, this method will enable the rapid design and fabrication of bio-inspired architected matter with multi-dimensional, hierarchical architectures composed of myriad materials.