Bent Into Shape: Mechanics and Geometry of Self‐Assembled Metal Nanomembranes

ABSTRACT This work provides crucial foundational knowledge for creating self‐assembled, conductive 3D structures, such as rolled‐up tubes, helices, or curves. Potential applications for these structures are vast, including microactuators, metamaterials, antennas, inductors, transformers, and slow‐wave structures. In particular, this paper elucidates the science underlying the self‐assembly of ultra‐thin metal sheets—or nanomembranes—while presenting a broadly applicable approach for predicting their equilibrium 3D geometry after release from their substrates. The method relies on in‐situ stress measurements during metal deposition, in conjunction with continuum‐mechanics models that quantify how complex internal stresses dictate the curvature of these self‐assembled structures at equilibrium. A key finding is that complex residual stress profiles in physically deposited metal layers allow tailoring the radius of curvature of assembled 3D structures over nearly five orders of magnitude. Furthermore, experimental results show that the width of metal nanomembrane ribbons is a critical factor in defining their final self‐assembled shapes.