Novel 3D-Printed Hybrid Auxetic Mechanical Metamaterial with Chirality-Induced Sequential Cell Opening Mechanisms

New hybrid auxetic chiral mechanical metamaterial are designed and fabricated via multi-material 3D printing. Due to the chirality-induced rotation, the material have unique sequential cell-opening mechanisms. Mechanical experiments on the 3D printed prototypes and systematic FE simulations show that the effective stiffness, the Poisson's ratio and the cell-opening mechanisms of the new design can be tuned in a very wide range by tailoring two non-dimensional parameters: the cell size ratio and stiffness ratio of component materials. As example applications, sequential particle release mechanisms and color changing mechanisms of the new designs are also systematically explored. The present new design concepts can be used to develop new multi-functional smart composites, sensors and/or actuators which are responsive to external load and/or environmental conditions for applications in drug delivery and color changing for camouflage.