Programmable, active lattice structures: Unifying stretch-dominated and bending-dominated topologies

Cellular solids are often classified as stretch-dominated or bending-dominated structures. While the latter is suitable for energy absorption, the former is used in lightweight, load carrying applications. Developing a unified structure that can perform both tasks remains a challenge yet would be highly advantageous in applications such as space and robotics, where a structure is required to multi-task, e.g. provide energy absorption during launch and also load carrying strength during operation. In this paper, we introduce programmable active lattice structures (PALS) that are designed to undergo a controlled topological transformation when subjected to a heat stimulus. This transformation is realized by the inclusion of active programmable joints that enable switching between a bending-dominated and a stretch-dominated topology through changing the nodal connectivity in the lattice structure. Numerical simulations and experimental results verify the intended behavior. By switching between the two topologies, the demonstrated active lattice structures feature the unique capability to tune their mechanical properties in real-time to react to changing performance requirements during operation with potential application to space structures and robotics.