Single-mask microfabrication of three-dimensional objects from strained bimorphs

Recently, techniques known as 'micro- origami' or 'strain architecture' have emerged for the fabrication of out- of- plane micro- and nanostructures by relaxation of a pair of strain- mismatched thin films. Applications of such structures include optical reflectors, actuators and micropositioners. We illustrate how control of the folding order can generate complex three- dimensional objects from metal- oxide bilayers using this approach. By relying on the fact that narrower structures are released from the substrate first, it is possible to create multi- axis loops and interlinked objects with several sequential release steps, using a single photomask. The structures remain planar until released by XeF2 dry silicon etching, making it possible to integrate them with other MEMS and microelectronic devices early in the process.