|
Origami has gained attention in the microfabrication community as it has enabled applications including micromirrors, encapsulation devices, and microgrippers. Yet, fabrication methods for origami systems available at millimeter and sub-millimeter scales are of narrow scope with product-specific synthesis strategies. Therefore, generalized fabrication methods for origami at these scales emulating additive manufacturing are of great interest. The small length scales of these systems require the implementation of self-folding or assisted folding methods as the fabrication approaches. In this work, a self-folding method and an assisted folding method are demonstrated as origami fabrication strategies. Single-layer films of photopolymer with patterned properties along their in-plane domain are used to create the planar precursors of the origami structures. The properties of the films are patterned by controlling their crosslinking density via a double-exposure photolithography process. For the assisted folding method, surface tension of a droplet is used as the actuation mechanism. Compliant fold regions made of less-crosslinked photopolymer connect relatively stiffer face regions. Upon depositing a droplet on the films, bending deformation localized at the compliant folds is enabled. For the self-folding method, the photolithography process is devised such that developer solution is inhomogeneously absorbed throughout the cross-section of the fold regions. This inhomogeneity in concentration leads to local bending when the developer is released via heating. This diffusion-based self-folding method allows for programming of the folds to attain targeted fold angles. Both methods, enabled by patterned films produced using double-exposure photolithography, show promise for freeform fabrication of millimeter and submillimeter origami systems.
|
