Photodirected 2D-to-3D morphing structures of shape memory polycaprolactone/W18O49 nanowires composite film

Abstract

Shape memory materials possess programmable complex and large deformations towards external stimuli, which are particularly essential for their potential applications. For the transformation of planar two-dimensional (2D) structures into complex 3D structures, the design of asymmetric or bilayer thin sheets is usually required. In this paper, we propose a facile strategy to achieve these complex 3D structures that can be transformed to various pre-determined shapes sequentially by laser-triggered site-specific deformations. The response of shape memory polycaprolactone (PCL) to laser is realized by physically doping W18O49 nanowires into the cross-linked PCL diacrylate matrix. When irradiated by 98 mW cm−2 laser, the pre-stretched PCL/W18O49 film shows an out-of-plane bending deformation due to the temperature gradient and single-domain orientation on the thickness between the upper layer and lower layer. The bending rates and amplitudes of the film can be tailored by adjusting the parameters of irradiation time, the film thickness as well as the pre-stretch strain. Remarkably, the pre-stretched film can automatically bend in more intricate complex deformations by integration with kirigami cuts in planar. Finally, we demonstrate that by activating the dynamic transesterification reaction within the same film, it can also achieve the 2D-to-3D transformations. With these decent features, this kind of novel PCL//W18O49 film shows great potential in the field of biomedical devices or soft robotics.