Programmable Mechanical Metamaterials with Tailorable Negative Poisson’s Ratio and Arbitrary Thermal Expansion in Multiple Thermal Deformation Modes

Abstract

Mechanical metamaterials pave a way for designing and optimizing microstructure topology to achieve counterintuitive deformation including negative Poisson’s ratio (NPR) and negative thermal expansion (NTE). Previous studies were always limited to single anomalous mechanical or thermal deformation, but current applications for high-precision mechanical or optical equipment always require their combination and customized and anisotropic deformation parameters. This work develops programmable two-dimensional (2D) mechanical metamaterials based on chiral and antichiral structures constructed with curved bimaterial strips to produce tailorable NPR and arbitrary thermal deformation. The coefficient of thermal expansion of the mechanical metamaterials is tunable on a large scale across negative, near-zero, and positive values depending on the bimaterial configurations and geometrical parameters of curved strips, while the value of NPR is mainly determined by the radian. Furthermore, it is programmable by coding the unit cells to exhibit customized and anisotropic thermal deformation combining homogeneous, gradient, and shear modes. The proposed mechanical metamaterials are fabricated by multimaterial three-dimensional (3D) printing, and the unusual deformation modes are verified experimentally, which is well in agreement with the results of finite element analysis. This work demonstrates a feasible approach to achieving customized mechanical and thermal deformation through easy block building for specific engineering applications including eliminating thermal stress, shape morphing, and smart actuators.

Research progress and development trend of smart metamaterials

“…Under the external stimulus, the shape, property or function of the object will change with time. Stimulus-responsive shape memory materials based on 4D printing have the advantages of simple manufacturing process, large SMMs have gradually become a new protagonist in the field of materials and have been endowed with richer functional properties, including reconfigurable [65, 66], programmable [67], elastic wave propagation control [68,69] and mechanical computing [70,71]. et al In the future, the functional properties of natural materials will gradually diminish.…”

Advances in autonomous materials and structures

“…More recent efforts aim to tackle this issue with a heavier focus on developing new classes of structure-dominated materials and in particular active metamaterials [15] [16] [17]. Metamaterials exhibit usual characteristics while excited by external perturbations, such as negative properties [18] [19] [20] [21], ultra-properties [22] [23] [24] and extremal properties [25] [26] [27]. They have gained significant attention due to their potential to serve as novel micro-engineered platforms to achieve multifunctionality.…”

3D Chiral Energy-Absorbing Structures with a High Deformation Recovery Ratio Fabricated via Selective Laser Melting of the NiTi Alloy

“…With the development of mechanical metamaterials, researchers have observed that metamaterials prepared by designing structures exhibit better energy absorption properties than single materials. Mechanical metamaterials − are typically periodic assemblies of three-dimensional (3D) lattices designed to exhibit exceptional mechanical properties, such as lightweight, high specific stiffness, high specific strength, negative Poisson’s ratio, , excellent energy-absorbing capacity, , and impact resistance . The rapid development of additive manufacturing (AM) technology has facilitated the design and fabrication of complex lattice metamaterials, including honeycomb structures, octet truss, octahedrons, body-centered cubes (BCCs), , face-centered cubes (FCCs), and chiral structures .…”