Hierarchical metal/polymer metamaterials of tunable negative Poisson’s ratio fabricated by initiator-integrated 3D printing (i3DP)

Abstract

Metamaterials with artificially designed architectures can achieve unique and even unprecedented physical properties, which show promising applications in actuators, amplifiers and micromechanical controls. An initiator-integrated 3D printing technology (i3DP) was applied in this study to create scalable, metal/polymer meta-mechanical materials, which can gradually achieve negative Poisson's ratio, high strength and ultralow density, as well as high compressive and super-elastic behavior. The i3DP was enabled by integrating an atomic-transfer radical polymerization (ATRP) initiator with UV-curable resin, followed by polyelectrolyte brushes (PMETAC) grafting via surface-initiated ATRP and thereafter electroless plating to form metal coatings. Compared with polymer structures, the compressive stress of metal-polymer structure can be doubled when deposited with a 190 nm copper layer. The hollow metallic materials possess a tunable Poisson's ratio, and the highest average recoverability, which can recover nearly completely to their original shape after over 30% compression. Overall, this i3DP approach provides meta-structures with substantial benefits from the hierarchical design and fabrication flexibility.

Mechanical Metamaterials on the Way from Laboratory Scale to Industrial Applications: Challenges for Characterization and Scalability

“…The vast majority of published metamaterials are made out of polymers as they can generally accommodate larger deformations [2,3,16,27,37,[41][42][43]. However, it is important to remember that polymers can exhibit viscoelastic properties that will influence the overall mechanical properties, especially under loading conditions [44].…”

“…Metal-polymer composite metamaterials are achieved by polyelectrolyte-brush-assisted electroless plating (ELP) of copper. Etching of the interior polymer structure leads to hollow metallic metamaterials [43].…”

“…Optical imaging techniques as well as scanning electron microscopy are used to accompany mechanical testing (see Section 4.1) [27,43,54,79,92]. X-ray tomography gives a three-dimensional insight into the geometry.…”

Strain Rate Effect on Mechanical Properties of the 3D-Printed Metamaterial Foams With Tunable Negative Poisson’s Ratio

“…Adopting an assembly method, Wang et al (2018b) fabricated 3D doublearrow-head NPR foam structure and studied their mechanical properties. By using an initiator-integrated 3D printing technology, Zhang et al (2018) introduced metal/polymer reentrant foams with tunable NPR. Based on a classical re-entrant structure, Chen et al (2018) proposed three kinds of novel lattice foams with NPR, which showed enhanced energy absorption capacity, stiffness, and strength.…”

Additively manufactured AlSi10Mg inherently stable thin and thick-walled lattice with negative Poisson’s ratio

“…According to Li et al [110], the most significant advantage of developing − materials are their potential to be tunable [111][112][113]. This allows for targeted failure strain, elastic modulus, and strength while featuring scalable unit-cells for a wide range of applications [114].…”