Programmed Shape-Morphing Material Using Single-Layer 4D Printing System.

The single-layer 4D printing technology that can be controllable in response to external stimuli is a tremendous challenge in many areas, including smart materials, robotics, and drug delivery systems. The single-layer 4D printing technique was enabled by light-focusing, which results in the difference of mechanical properties such as the coefficient of thermal expansion or Young's modulus between focused and unfocused regions. However, 4D printing to the desired shape using single-layered material is challenging. In this paper, we demonstrate the programmed shape morphing by patterning both the static and shape-morphing layers using a single-layer 4D printing system. A shape-morphing layer is formulated by short-time (<3 s) illumination in UV light. Then a static layer is formulated by longer-time (>3 s) illumination in UV light. We expect this technique to lead to the development of micro-scale soft robots.