Development of new foldable polyethylene terephthalate bottles

An origami structure has the advantage of being light yet stiff and expandable. Some expandable structures are already widely available on the market, but although many have attempted to develop a polyethylene terephthalate (PET) bottle that is foldable in the axial direction without bending, such bottles are not yet on the market. The present work thus aims to develop a PET bottle that easily folds without bending. The initial model is generated with seven layers, of which five layers (i.e., excluding the lid and bottom) are set as spiral cylinder. This model can be folded rather easily without bending. However, the model springs back to almost its original height after compression. Thus, we develop new types of PET bottle with two or three spiral layers to resolve this spring back issue. Our new design can insert the foldable layer into a non-foldable layer, such as a conical shell or cylindrical shell, to suppress the spring back after compression. Additionally, grooves between foldable and non-foldable layers in our new designs can further contribute to the trapping of foldable parts. Moreover, our new design can achieve partial compression to reduce the height of the bottle when the liquid is partially consumed