"Bend-and-Bond" Polymer Microfluidic Origami

We report the fabrication of polymer microstructures with inert surface finish by folding and self-bonding. Layers of off-stoichiometric thiol-ene-epoxy (OSTE+) were fabricated using UV photocuring (1
^st
curing step) of resin, which resulted in a malleable sheet with unreacted groups at its surface. The sheets were structured by either photomasking during the 1
^st
curing step or by cutting post-curing using xurography. The sheets were subsequently folded into a desired shape. Last, the folded structures were thermally cured (2
^nd
curing step), during which surfaces in contact with each other spontaneously bond, the polymer stiffens, the folding stress is released, and reactive surface groups are consumed. We used this unique bend-and-bond technique to demonstrate three sample structures: a multilayer microfluidic chip with crossing channels, a helical spring, and a functional mini windmill. We believe OSTE+ origami can find further applications in the fabrication of biochips and biosensors.