This talk will describe the use of light to induce folding or curving of initially flat polymer sheets. Regions of black ink patterned on 300 mm thick sheets of pre-strained polymer absorb the light and heat up the underlying polymer by the photothermal effect. The heat causes the polymer to relax and therefore shrink, which can induce self-folding. By changing the color of the ink and the wavelength of light, it is possible to control the sequence of folding to form more complex shapes. Self-folding is similar to origami but is done without direct human intervention. In addition to folding, recently we showed it is possible to achieve curvature by distributing grayscale ink across the surface. Doing so allows ‘strain programming’ of the surface, which enables the formation of 3D surfaces with curvature, including spheres. This helps solve the ‘map-makers problem’, which underscores the challenges of converting a flat surface to a sphere. In general, the appeal of this approach is that it utilizes two dimensional patterns (generated by inkjet printing or screen printing, for example) to create a variety of complex three dimensional objects. In essence, it allows shape memory polymers to be programmed using a variety of two dimensional patterning techniques and triggered using only light. In addition to light (LEDs, IR bulbs, and lasers), it is also possible to use other stimuli to direct the localized heating, including microwaves and Joule heating. The talk will discuss the use of light, lasers, and other electromagnetic radiation (e.g. microwaves) to induce folding, the use of color to control sequence of folding, and the use of distributed ink patterns to create more complex objects with curvature.

Using light to actuate polymer sheets

2019 Spring National Meeting

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