Capillary origami as a new method for obtaining folded structures with interior nanoparticle coating

Abstract We introduce capillary origami as a new method to obtain 3D enclosures with coated nanoparticles on their inner surfaces. When a liquid droplet that contains nanoparticles is placed on the surface of a thin and flexible membrane, the membrane folds around the droplet. As the droplet evaporates nanoparticles deposit on folded surfaces and eventually a 3D enclosure is obtained. In this study, both magnetic iron-oxide (Fe3O4) and gold (Au) nanoparticles are used and it is shown that with both types of nanoparticles the enclosures remain closed after the complete evaporation of the droplet. It is also demonstrated that the magnetic nanoparticles can be concentrated at a chosen location on the folded geometry by using a magnet during evaporation. The origami based coating method is applied on different geometries and distribution of nanaparticles depending on the surface orientation is quantified. As part of the study, the capillary origami behavior of liquids with and without nanoparticles is compared.