The ability to fold containers flat is invaluable to the packing industry. Packing companies mainly use either flat-packed, rigid boxes that are open at both ends and have to be fastened shut at the bottom before use, or flexible bags that can be folded flat but are not as strong.

Now Zhong You and Weina Wu at the University of Oxford, UK, have mathematically devised a hybrid solution, featuring advantages of both systems. Their complex folding pattern of 28 creases forms the design for a rigid bag with a closed bottom. They demonstrated their solution by making a bag out of paper bonded to steel sheets and folding it flat (pictured). This is the first time a solution has been found to fold flat a rigid bag that is taller than half its depth.

Credit: R. SOC.

Proc. R. Soc. A doi:10.1098/rspa.2011.0120 (2011)