This talk will discuss a simple approach to shape-program 2D sheets of polymer into 3D objects. Self-folding is a deterministic ‘origami’ process that causes a predefined 2D template to fold into a desired 3D structure with high fidelity. We achieve self-folding by locally heating pre-stressed polymer films. The heat causes the polymer to locally relax (i.e., shrink) and induces a folding response. The heat can be delivered using patterned light, patterned inks that absorb light, and patterned inks that absorb microwaves. Self-folding takes advantage of the multitude of available 2D patterning techniques that can be employed to pattern these inks (e.g., lithography, inkjet printing, screen printing). Self-folding is attractive as a cost-effective 3D fabrication strategy for applications such as packaging, robotic actuators and sensors, biological devices, solar cells and reconfigurable devices. This talk will focus on our recent efforts to model the mechanics of the self-folding process using finite element modeling, to utilize microwaves as a stimulus to induce self-folding, and to achieve sequential folding (i.e., folding individual hinges in a controlled sequence to achieve more complex geometries). The latter is interesting because it allows individual ‘hinges’ to fold in response to light depending entirely on the color of the light and the color of the ink that absorbs the light; that is, using color theory. The ability to control sequence of folds enables more complex structures to be generated by self-folding. In addition, the talk will discuss efforts in our group to control curvature of sheets using similar principles of local delivery of heat to pre-stressed polymer sheets, but rather than localizing it to a hinge, the heat is applied over broader areas to induce curvature.

Shape-shifting polymer sheets using light

254th National Meeting (2017)

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