Mechanical metamaterials based on snap-through instability structures: classification, applications, and prospects

Snap-through instability-based mechanical metamaterials (SIMMs) with bistability, multistability, negative stiffness, or excellent energy absorption and dissipation performance play an important role in various advanced functional applications. They can serve as energy absorbers, energy dampers, or mechanical memory and logic computing devices, while also providing amplified force output and faster response time in flexible robots, or implementing sensing functions combined with piezoelectric or triboelectric electricity. However, thus far, research on SIMMs that have non-fixed boundary constraints, proactive responsiveness, multi-physical field cross-coupling, and deep information processing capabilities is still facing significant challenges, potentially hindering the development and cross-field comprehensive applications of truly intelligent SIMMs. Our objective is to furnish a concise categorization of SIMMs and offer direction for innovative design and functional implementations. We have emphasized that the non-fixed boundary constraint will expand the design possibilities, while the use of stimulus-responsive materials and 4D printing technology will create novel opportunities for the design of SIMMs. These advancements are expected to achieve innovative mechanical properties and functions.