New Technique Creates Complex Structures

CHAMPAIGN, Ill., April 19 (UPI) — University of Illinois scientists have created a printing technique that produces complex structures from flat sheets of direct-printed titanium hydride ink.

The researchers led by Professor Jennifer Lewis said small, intricate shapes made of metals, ceramics or polymers have a variety of applications, from biomedical devices to electronics to rapid prototyping.

University officials said one method of fabricating such structures is by direct-write assembly, which the Lewis group helped pioneer. In that approach, a large printer deposits inks containing metallic, ceramic or plastic particles to assemble a structure layer by layer. Then the structure is annealed at a high temperature to evaporate the liquid in the ink and bond the particles, leaving a solid object.

However, as more layers are added, the lower layers tend to sag or collapse under their own weight.

“Most of our inks are based on aqueous formulations, so they dry quickly. They become very stiff and can crack when folded,” Lewis said. The challenge was to find a solution that would render the printed sheets pliable enough to manipulate, yet firm enough to retain their shape after folding and during annealing.

Lewis, postdoctoral researcher Bok Yeop Ahn and colleagues said they solved the problem by mimicking wet-folding origami, in which paper is partially wet to enhance its ability to fold.

The research that included Professor David Dunand of Northwestern University appears in the early online edition of the journal Advanced Materials.

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