LLNL Engineers Unveil 3D Polycatenated Architected Materials (PAMs) with Solid and Liquid-Like Properties

Lawrence Livermore National Laboratory (LLNL) engineers, in collaboration with CalTech and Princeton University, have introduced 3D polycatenated architected materials (PAMs), exhibiting both solid and liquid-like properties. Published in *Science*, the study details how these intricate structures, composed of interconnected loops or cages, dynamically respond to external forces by expanding, contracting, or morphing. LLNL staff scientist Xiaoxing Xia explained that PAMs' interlocked building blocks allow greater freedom of movement compared to rigid lattices, enabling them to behave like both a liquid and a solid under different conditions. Experiments revealed gravitational relaxation, where PAMs change shape in response to gravity, suggesting applications in stimuli-responsive materials, energy-absorbing systems, and morphing architectures, especially in low-gravity environments. The team demonstrated PAMs' length-scale-independence, fabricating them at both macro and microscale levels while maintaining consistent mechanical responses. This scalability suggests applications ranging from microscopic medical devices to large-scale architectural components. Aerospace engineers could design aircraft components balancing strength and efficiency, while PAMs' energy absorption capabilities could enhance protective gear like helmets and body armor. Electrostatic responsiveness is another key aspect. Coating microscale PAM samples with copper revealed that electrostatic forces cause the rings to repel each other, leading to rapid, reversible transformations. This suggests potential use in smart systems reacting to electrical signals, such as robotics or wearable tech that adjust in real time. Challenges remain in large-scale production due to variations in fabrication techniques. LLNL researchers are developing new printing techniques to streamline fabrication. The team continues to investigate PAMs' properties under varying environmental conditions to ensure real-world durability and performance.