Mechanical metamaterial continuum materials realized through 3d printing using compliant mechanisms techniques

Abstract

Recently developed classes of mechanical metamaterials that couple twisting with linear and volumetric expansion show great promise for the fields of soft robotics, deployable structures, and medical devices. These twisting auxetics can convert torque from conventional motors directly into expansion. Previously they have been realized only as assembled units, but in order to be usable in metamaterial structures they must be fabricable as a single continuum of material. However, the complex joints and relations between layers of material are not compatible with conventional fabrication processes. We use mono-material 3D printing of compliant materials and compliant mechanism design techniques to produce 3D printable continuum material versions of these twisting metamaterials. We show that we can produce continuum analogs of rotating bilayer joints, angle preserving joints, and multi-component joints and replicate the bilayer polyhedral auxetics. We show how these techniques can be used to fabricate planar structures that can be folded into 3D objects. These printing and design techniques allow for the easy and scalable fabrication of twisting auxetic metamaterials which can be actuated with motors.