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Ying Liu, et al. from Michael Dickey’s Lab at North Carolina State demonstrate how simply using an inkjet printer to put black lines on shrinky-dinks, one can transform them into a heat activated self-folding material. (Paper.)
The idea is very simple. When a light is shone on the taped up shrinky-dink, the black tape absorbs more energy, and thus the area under the tape heats up faster than the uncovered material. Since shrinky-dinks contract when heated, a hinge is created. By varying the width of the tape, the rate of closure and the resultant angle can be controlled.