Credit: Bok Yeop Ahn and Jennifer A. Lewis.

As you can see above, ACerS Fellow Jennifer Lewis and her team at the University of Illinois at Urbana-Champaign have figured out how to make intriguing and beautifully simple (yet complex) origami structures by bending and folding planar lattices. The lattices are made by extruding “inks” of ceramic, metal or polymeric materials using a precise, direct-write method.

In general, beads of inks are laid down in a particular pattern and allowed to partially dry. They are then trimmed, folded and finally annealed to complete the structure.

Direct writing of lattice. Credit: Bok Yeop Ahn and Jennifer A. Lewis.

But this makes it sound much too easy. In fact, Lewis,  Bok Yeop Ahn, David Dunand and others in her team faced significant materials and technical challenges. In a University press release, Lewis says, “Most of our inks are based on aqueous formulations, so they dry quickly. They become very stiff and can crack when folded.”

She says the challenge, then, 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 annealing. The answer came by combining  wet-folding origami techniques (where paper is partially wetted to enhance its foldability) with special inks containing a mixture of fast- and slow-drying solvents.

The combination yields a lattice that can can be partially dry but flexible enough to fold through multiple steps. The origami crane – requiring 15 steps – allows them to demonstrate the agile possibilities of their methods.

For Lewis, a professor of materials science and engineering and the director of the university’s Frederick Seitz Materials Research Laboratory, these structures have a serious side. “By combining these methods, you can rapidly assemble very complex structures that simply cannot be made by conventional fabrication methods,” Lewis says.

Practically speaking, this technique could provide an alternative to existing “rapid prototyping” approaches to build scaffolds for tissue engineering. There are limits to rapid prototyping, which builds 3D structures by laying down layer after layer of material, due to the sagging of lower layers or compressing under their own weight.

Lewis’ team’s method could create light, strong structures that can be bent, folded and rolled out of lattices  formed from nearly any pattern. Stents, bone-repair scaffolds, biomedical devices or even catalytic substrates are possible.

Samples of stents and other structures. Credit: Bok Yeop Ahn and Jennifer A. Lewis.

Dunand says the next step is to try larger and much smaller structures and test ink compositions that would contain other ceramic and metallic materials.

“We’ve really just begun to unleash the power of this approach,” Lewis said.

A short video providing a closer look at some of the structures is available here.

Adding . . . Advanced Materials published a paper on this work, and if you look in the comments, the editor of the magazine has kindly posted a link for a free download of the paper.