4D printed shape memory metamaterials with sensing capability derived from the origami concept

Mechanical metamaterials have unprecedented properties that contribute to the development of science and technology. However, once the mechanical metamaterials are fabricated, the single configuration will limit their application, especially in areas requiring rich programmability and efficient shape reconfigurability, etc. To break through this limitation and explore more potential of mechanical metamaterials, this work proposes a novel design strategy for 4D printed metamaterials with programmable stiffness. Deriving from the origami concept, the stiffness of the structure can be adjusted not only by changing the geometric parameters but also by changing the geometric configuration utilizing the shape memory property. Through numerical simulation, theoretical analysis and experimental tests, the design strategy is verified in the 4D printed mechanical metamaterials. With this strategy, the stiffness of the structure can be adjusted, and the mechanical programmability, shape reconfigurability and adaptability can be significantly improved. Utilizing excellent energy absorption performance, we design and fabricate a kind of shoe sole. By integrating the sensor function of the Triboelectric Nanogenerator (TENG) into the sole, gait monitoring is successfully realized. The 4D printed shape memory metamaterials show extraordinary potential in the field of programmable shock absorption and intelligent monitoring.