Bidirectional Folding with Nanoscale Sheets for Autonomous Micro-Origami

We present micron sized self-folding devices that consist of nanometer-thin metal oxide bilayers, built with conventional semiconductor fabrication methods. A bending response originating from strain differentials within these bilayer stacks is used as the fold actuation mechanism. This strain differential induced bending is controlled by ion exchange reactions in our nanoscale sheets, which can produce radii of curvature at the order of 10 um within seconds. By lithographically patterning these sheets, we localize the bending and create microscale devices that can sense chemical changes in their environment and respond by changing configurations according to prescribed mountain-valley fold patterns. Finally, we show that our fabrication approach offers a range of chemical, electrical and biological functions as well as a path to sequential folding through the programming of stacks.