The authors used a 3-D printer to make right-angle hinges from the shape-memory polymers VeroWhite (a rigid plastic at room temperature) and Tangoblack (a rubbery polymer). The bending rates of the hinges were fine-tuned by varying the ratios of the two components.
The researchers flattened their boxes at 90 ºC and set the flattened shapes at 10 ºC. To reconstruct the boxes, they heated the flat sheets in a water bath at 90 ºC (see video).
The time it takes each hinge to recover its 90º bend depends on the glass-transition temperature of the polymer mixture from which the hinge is made. This feature allowed the authors to fold and lock the sides in sequence, in much the same way that a person folds and locks panels to assemble a shipping box. (Sci. Rep.DOI: 10.1038/srep13616)