Fabrication of three-dimensional microstructures using capillary forces

In this paper we describe the fabrication of threedimensional microstructures by means of capillary forces. Using an origami-like technique, planar structures are folded to produce 3D-objects. To this purpose use is made of capillary interactions and surface tension forces. Capillarity is a particularly effective mechanism since it becomes dominant at small scales (where surface tension forces dominate over bulk forces), the process benefits therefore from miniaturization. Planar microstructures of silicon nitride of various geometries with lateral dimensions of about 100 mm and thickness 1 mm and thin hinges for rotation, have been fabricated. Preliminary experiments in which liquid drops are deposited on these structures show that mechanical bending forces can be overcome and that folding out-of-plane can be realized. Capillary folding is therefore shown to be a very promising technique to fabricate 3D micro- and nanostructures.