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Harvard lab developing 3-D ‘inks’ that can replicate human cells

Professor Jennifer Lewis in her lab at the Harvard School of Engineering and Applied Science.Lane Turner/Globe Staff/Globe Staff

A two-ton printer the size of a small car takes pride of place in Jennifer Lewis’s lab, among half a dozen machines arrayed in a basement on Harvard’s campus. But on a recent weekday morning the room is calm, with only the tunes from a Pandora station (“Lynyrd Skynyrd Radio”) piercing the calm.

Lewis, a professor at the Harvard School of Engineering and Applied Science, is among a generation of engineers who are radically expanding the capabilities of 3-D printing.

That technology emerged about 30 years ago as a way to make fast, precise models of a car, or a plane, or a bridge, before building the real thing. The chief material by far was plastic, heated until molten, and then passed through a nozzle like really hot glue and laid down layer after layer to form a shape first modeled on software.


Decades on, the Lewis lab is in the business of making “ink” for 3-D printers, so that useful, functional objects made of a variety materials, not just plastic, can be produced. Loaded into a cartridge like an office printer, these materials aren’t sprayed on paper.

Instead, they are liquefied and extruded onto a base of choice, maybe paper, maybe metal, maybe a flexible polymer. The lab’s primary goal is to expand the type of objects that can be made in a 3-D printer.

“If we can make matter that affects people’s lives in a material way that would be a tremendous thing to accomplish,” Lewis said.

One team at the lab is making strides developing inks made of living cells and devising printing tools that can use them.

Earlier this month, the team showed it was possible to assemble a chunk of tissue that, for the first time, lived for six weeks and developed into a bone-like mass. It was able to survive because the structure included hollow channels, similar to blood vessels. Media with nourishment and oxygen sluiced through the channels, reaching even the deepest set of cells.


“Creativity is the limit here in terms of what’s possible,” said Michael McAlpine, a professor at University of Minnesota who is simultaneously working on printing living tissue and electronic inks. In a field in which researchers are racing to run every material imaginable through a printer, the Lewis lab has the edge in working with biological tissue. “She’s certainly a pioneer in doing that,” he said.

One of the lab’s key achievements is creating inks containing metals that could extend 3-D printing into electronics manufacturing.

Plastics must be heated to high temperatures to flow through a printing nozzle, but the Lewis lab specialty is inks that are solid when stored but liquid when they are compressed in a printing nozzle. Once extruded, they solidify.

“Our inks are like thick toothpaste or peanut butter,” said Scott Slimmer, the lab manager at the Lewis lab.

Lewis is really excited about the fruits of collaboration between the groups printing electronics, and the team printing cells.

“We ultimately think there are projects at the interface ... where we can embed sensors,” Lewis said. A possible product: Living tissue chunks with sensors that could monitor how healthy the cells are, or how they respond to stimuli like doses of a new drug.

Like many researchers in Greater Boston, Lewis is channeling some of her efforts into converting lab breakthroughs into commercial products. Voxel8, a company she founded in 2014, is making desktop-sized printers that can print plastic as well as metal objects.


“We’re envisioning things like medical devices, wearable devices,” said Daniel Oliver, a Harvard Business School graduate who cofounded the company with Lewis.

So far, backers including 3-D design giant Autodesk; In-Q-Tel, an investment firm that supports the work of the Central Intelligence Agency; and venture capital firms Braemar Energy Ventures and ARCH Venture Partners have invested $12 million in the company.

“There had been nothing of that level in the industry yet,” said Duann Scott, business development manager at the investment arm of Autodesk. The standard, he said, is printers that can print quickly, using only one material, yielding prototypes rather than finished products.

Oliver’s immediate goal is to pitch their printers (about $9,000 each) to research labs within big manufacturing companies, with the hope that designers and engineers who tinker with the instrument can modify it to their particular manufacturing needs over the next few years. By that point, Voxel8 expects to have industrial-sized models of their desktop models available for purchase.

Barely a year after launch, MIT Technology Review named Voxel8 to its list of 50 Smartest Companies and Lewis found herself on Fast Company’s list of Most Creative People. But Lewis says her keenest interest still lies in cutting-edge lab research.

“I never expected to wind up at a place like Harvard doing the things I’m doing,” Lewis said.


Despite the crush of e-mail, the daily demands of running a 25-person lab, and finding funds for research at a lean time, Lewis seems to be having fun. A high point, she said, is sitting in lab meetings and having her team surprise her with evidence of a small success or discovery.

“Those are the best moments for me,” she said. “That’s the research group. They’re making it happen.”

Students Jochen Mueller and Mark Skylar-Scott set up a multinozzle for a 3-D printer in Lewis’s lab.Lane Turner/Globe Staff

Nidhi Subbaraman can be reached at Follow her on Twitter @NidhiSubs.