We discuss the self-folding of patterned metallic sheets using both differential stress and surface forces. The advantageous characteristics of the technique include, (a) The creation of 3D patterned corrugated metamaterials with pattern resolution limited only by that of planar lithography. Since planar lithography is highly versatile, a variety of patterns with different sizes and shapes can be formed. (b) The hands-free and wire-free self-folding of these materials use two orthogonal forces derived from the release of residual stress and the minimization of surface tension. Hence, this process is highly parallel and scalable allowing such materials to be mass produced. (c) Finally, the edges of the materials self-align and seal due to capillary forces of the liquid hinges—this self-sealing enhances overall rigidity and strength of the materials.
Consequently, the self-folding of patterned and sealed “egg-crate” shaped metamaterials was realized. Patterns were incorporated in the form of “smart” patches on the walls of the egg-crates which can be selectively functionalized with biomolecules. Apart from the intellectual appeal of these hands-free, self-sealing materials, we envision applicability of these egg-crate like microstructures in lab-on-a-chip assays as functionalized microwells and as light weight mechanical metamaterials.