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 XeF 2 dry silicon etching, making it possible to integrate them with other MEMS and microelectronic devices early in the process.

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In this paper, we explore microfabricated bistable actuators released as thin films from a silicon wafer. The actuators are based on a serpentine design where two cantilevers are coupled at the tips by a thin-film bar. These devices are parameterized by two lengths: cantilever length and the length of the coupling bar. These two dimensions are systematically varied to study the effect of design parameters on bistability. The three-dimensional devices have extremely large deflection (hundreds of microns rather than tens of microns for most planar microactuators of similar size) and are thermally actuated out of the plane of the wafer by applying a bias across either the left or right side of the serpentine. The bistability of these devices is evaluated using electron and optical microscopy. Potential applications include non-volatile mechanical memory, optical shutters, and reconfigurable antenna elements.