Origami Folding of Polymer Sheets in Response to Light

Self-folding is a self-assembly process that causes a predefined 2D sheet to fold into a desired 3D structure with high fidelity. Self-folding can be applied in the fields of actuation, sensors, and packaging. Our method uses ink printed on pre-stressed polymer sheets using a desktop printer to define ‘hinges’. An intrinsic property of the polymer is that it can shrink 50% in both x and y dimensions in plane when it is heated uniformly above »100°C. When exposed to an infrared heat lamp, the polymer underneath the inked hinges absorbs the light more effectively than the rest of the sheet, which induces localized polymer shrinkage and thus, folding.  This approach provides a simple and inexpensive method to induce self-folding in a hands-free manner.  It can be utilized to form complex 3D shapes and can produce upward or downward folds (i.e., toward the light or away from the light).  We will describe the application of folding into complex origami structures and folding/unfolding pathways.  Also, we will present folding sequences by varying the light sources and hinge colors.