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Photo-activated olefin metathesis enables 3-D printing of structural components

by Marc S. Reisch
October 31, 2016 | A version of this story appeared in Volume 94, Issue 43

A schematic of a 3-D printing process using olefin metathesis polymers.
Credit: PolySpectra/C&EN/Shutterstock
A base-ring opening metathesis monomer, function-enhancing additives, and a latent UV-activated ruthenium catalyst are mixed and placed in a 3-D stereolithography printer tray. Patterned UV light projected through a window on the tray bottom cross-links the mixture to form an object. Unused ink can be recycled.


Launched: 2015

Headquarters: Berkeley, Calif.

Focus: 3-D polymer printing

Technology: UV-activated olefin metathesis

Founder: Raymond Weitekamp

Funding or notable partners: Department of Energy Advanced Manufacturing Office

Today’s polymers for three-dimensional printing work well to help designers create product prototypes. But to make durable plastic parts for consumer use, manufacturers still turn to traditional casting and molding technologies.

Start-up PolySpectra and its CEO, Raymond Weitekamp, have a better idea: Improve 3-D printing with the help of olefin metathesis, and forget about the casting and molding. Such an advance, he says, would “democratize manufacturing by lowering the cost of taking a new idea from conceptualization to realization.”

PolySpectra engages the power of stereolithographic printing, a computer-guided 3-D printing technology, around since the 1980s, that cures polymers with patterned ultraviolet light. Unlike 3-D printing based on resin filaments, where printers painstakingly layer strands of heated polymers to form components, stereolithographic printers rapidly form parts with fine details. But those parts are often not very stable or durable.

Most of the stereolithographic printers depend on acrylate or epoxy polymers, “which tend to be brittle and break if dropped,” Weitekamp says. Soon, he says, printers will be able to swap in “new photopolymers we have developed with drastically higher working temperatures and greater toughness.”

Key to PolySpectra’s polymers is a light-activated ruthenium catalyst Weitekamp discovered four years ago while a Ph.D. student in the CalTech labs of olefin metathesis leader Robert Grubbs and plasmonics expert Harry Atwater.

Light is not a factor in polymerization based on traditional ring-opening metathesis. What Weitekamp did was to find a cost-effective way to block ruthenium catalyst activity until the catalyst is exposed to UV light.

The material PolySpectra is developing has three basic ingredients: an olefinic monomer, Weitekamp’s light-activated ruthenium catalyst, and functional additives. Poured into a stereolithographic printer tray, the mixture cures when exposed to patterned UV light that shines through a window at the bottom of the tray. A build platform raises the hardened resin object up from the tray layer by layer.

Objects produced with PolySpectra’s resin would be ideal for short-run production parts for which mold tooling costs would be excessive, Weitekamp says. One application could be making high-strength airplane parts with complex geometries.

Print worthy
Polyspectra video of a stereolithographic printer making an object using olefin metathesis inks.
Credit: PolySpectra

Future developments might include microfluidic devices that take advantage of the printing detail provided by stereolithography. Down the road could be medical implants with additives that attract and interact with human cells.

PolySpectra is supported through the Molecular Foundry research facility and the Cyclotron Road small-business incubator, both of which are funded by the Department of Energy and located in Berkeley, Calif. The firm is now raising a few million dollars from private investors, Weitekamp says. If successful, he’ll follow on the heels of competing start-up Carbon3D, which has attracted more than $140 million to develop its own novel 3-D materials and a proprietary printer.

Weitekamp’s technology combines new chemistry with the printers already installed in prototype facilities. “There’s an amazing hardware infrastructure out there now,” Weitekamp says. “We can help transform that hardware from a prototyping tool to a manufacturing platform.”

Real tough
PolySpectra video showing toughness of an object printed with its inks (right) versus competing inks (left).
Credit: PolySpectra

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