A device for maintaining the shape of footwear, both at the tip of a shoe as in the stiffener through a tension force against the tip and stiffener of the shoe, the same caused by the device snap-fitting and its natural tensioning element curved, is provided. Means for Solving the ProblemsThe surge absorber is comprised of a pair of terminal electrode members which are opposed to each other; and the insulation tube on which the pair of terminal electrode members are disposed on opposite ends thereof and that has a discharge control gas sealed therein. The method employs a sterolithography instrument, a solution comprising chains of one or more photocurable, bioerodable polymers and a photoinitiator, and a three-dimensional CAD image. The trough is provided therein with a connecting port. Embodiments of the invention allow the synthesis of nanoparticles, such as of single metals, metal alloys, or metal oxides, to a high concentration in a water base using a metal catalyst.