Functional mechanical metamaterials – development of programmable mechanical structures
In recent years, and with the continual development of Additive Manufacturing (AM) technologies, Mechanical Metamaterials (MMs) are explored for their programmable and tunable nature. This has opened a new design space into mechanical devices that utilise the structure of a material to perform a function, otherwise known as Functional Mechanical Metamaterials (FMMs). Material Jetting is used to build programmable MMs by combining elastic flexure elements to rigid beams. The proposed metamaterial controls the buckling response of a biased Von-Mises Truss through the actuation of unit cells to perform Boolean logic. By developing an anisotropic 3D unit cell and a bistable system for signal propagation, AND and OR logic gates have successfully been demonstrated in three different configurations, $zz$, $yy$ and $zy$-polarisation. Additionally, an SLA-printed compliant MM is successfully developed, combining anisotropic unit cells to coupled slender beams. The separation distance between the fixed ends of a slender beam can be used to tune the MM between monostable and bistable states. This behaves as a control system, allowing mechanical signals to pass only when the correct actuation pattern and force is applied. In both MM examples, textit{sense-decide-respond} logic sequences under mechanical actuation are demonstrated. These FMM implementations pose several advantages for use in larger combinatorial systems. Experimentation successfully demonstrates bistable wave propagation, allowing multiple mechanical signals to pass through larger structures in multiple planes. A compliant rod-logic FMM is developed, actuation of the structure engages a gating function that modulates mechanical signals through a plane. Finally, integrated multi-material FMM sensors are developed, highlighting the use of mechanical sensors in architected systems. The proposed FMMs have applications as nuclear safety devices, accelerometers in automobiles, and as a diagnostic tool in lattice-based crash helmets.
Functional mechanical metamaterials – development of programmable mechanical structures