Prestress-induced 3D assembly of soft material with programmable shape

Soft materials are widely employed in wearable electronics, soft robotics and biomedicine due to high deformability and superior flexibility. However, large deformability and flexibility in general come with highly nonlinear viscoelastic behavior, which poses great challenges for traditional polymer processing methods to manufacture these materials into three-dimensional (3D) structures with high precision. Converting flat soft materials into 3D forms through prestress is an effective solution for fabrication of complex 3D morphologies. However, the 3D shapes cannot be customized due to the limit of existent manufacturing strategy, which hinders further application. In this paper, we report a 3D-assembly strategy of customizable shape. It utilizes the spontaneous spring-back of pre-stretched elastomer film upon release as the driving force for shape transformation, creating 3D structure from flat two-dimensional (2D) configuration. Furthermore, the use of digital light processing technology ensures 3D morphologies to be constructed from programmable 2D configurations with high precision. Spiral band and double-curvature surfaces are created from designed 2D patterns as demonstration. In addition, we created a wearable luminous band that spontaneously wrap around fingers under stress relaxation. This work offers a straightforward, controllable, and transferable technique that is efficient for the creation of 3D soft structures.