Energy Barriers Measurement for Efficient Shape-Shifting in Multistable Lattice Metamaterials

Shape-shifting between stable states in multistable structures presents promising advantages for designing adaptive structures across various domains, including soft robotics and aerospace engineering. The efficiency of shape-shifting relies on overcoming the energy barrier that separates distinct stable configurations, necessitating efficient actuation strategies. This work addresses the challenges associated with quantifying the energy barrier in multistable metamaterials that utilize local, embedded actuation, a concept recently explored by the authors [1]. Conventional methods for measuring energy barriers struggle due to the inherent requirements of local actuation, which requires opposing forces and constant force directions throughout the loading process, along with unrestricted movement perpendicular to the loading direction. To address this, we introduce a novel bi-axial test rig tailored for typical multistable lattice metamaterials. This rig, employing an embedded actuator, accurately assesses the energy barrier between stable states by inducing shape-shifting. Our experimental setup incorporates two independent actuation systems operating at different length scales: one for globally applied axial compression and another for local triggering of shape-shifting. The obtained experimental data provide insights into the metamaterial's response to local, embedded actuation, demonstrating excellent agreement with finite element simulations and affirming the efficacy of our test setup in measuring the energy barrier. This work paves the way for efficient design and control of shape-shifting metamaterials by providing a reliable method for quantifying energy barriers.