The public imagination has been captured by 3-D printing in recent months, as people have used it to conjure up custom medical devices, a working handgun, and even an edible pizza. This spring, Staples became the first major retailer to announce that it would carry 3-D printers, putting the technology in the hands of the masses for about $1,300. (See "3-D Printers Are Saving Lives and Serving Pizzas.")
To Janine Benyus, a biologist, author, and innovation consultant, the 3-D printer revolution offers great opportunity, as well as risk. She hopes the technology can be improved by modeling it after natural processes. (See "What, Exactly Is a 3-D Printer?")
"It's going to start slow—people will make toys for their kids and so on," she predicts. But soon, people will be printing out increasingly sophisticated products, from home goods to shoes.
One big problem with 3-D printing in its current form, said Benyus, is that many of the printers rely on toxic building materials, in the form of an increasing array of polymers (plastics), resins, and metal powders.
"Some 'makers' [3-D printer users] are starting to see their skin reacting, and when you look at the material data safety sheets for these materials you see serious warnings," said Benyus. That's a concern, because people are using the printers in their homes and inhaling the fumes, she said.
"We shouldn't have to wash our clothes after we use a 3-D printer, or ask our sons or daughters to take out the hazardous waste trash," she said.
Instead, Benyus argues that all the materials used in 3-D printing should be common and safe for anyone to handle. They should be sourced from local feedstocks, and at the end of their lives, they should be "unzippable" into reusable materials.
Mirroring the Chemistry of Life
Benyus, who wrote Biomimicry: Innovation Inspired by Nature and co-founded the institute Biomimicry 3.8, would like to see a transition in manufacturing—from big, smoke-belching factories to small, clean desktop printers. The key to making it truly sustainable, she said, lies in mimicking how a natural ecosystem functions.
"Nature uses life-friendly chemistry, which is nontoxic and water-based, and which does not require high heat," said Benyus. In contrast, most of the products people use today have been forged in industrial-size furnaces, with a plethora of toxic solvents. A potato chip bag may seem like a simple item, but it is actually made up of several thin layers of different materials, one to make it strong, one to make it airtight, and so on.
But nature creates an enormous amount of diversity from a relatively small palette of materials. Most of the polymers in the natural world fall into about five classes, said Benyus. One is keratin, which makes up skin, hair, and feathers across the animal kingdom. Another is chitin, which makes up exoskeletons in arthropods. The way such basic building blocks are arranged, in terms of internal structure, results in extraordinary differences in animals' size, shape, color, and function—and it can also result in extraordinary strength.
For example, an abalone shell is stronger than high-tech ceramics because of its internal structure, said Benyus. Diatom shells are made of silica (glass), but they are extremely strong because of their stress-distributing pattern of holes.
The tough, lightweight structure of abalone shells could inspire efficient 3-D prints.
Photograph by Darlyne A. Murawski, National Geographic
Like nature, 3-D printers can excel at building complex structures from simple materials, said Benyus. Both use an additive process, meaning larger pieces are built up from smaller ones.
In contrast, conventional industrial manufacturing is typically subtractive: Pieces are cut out of rolls of prefashioned material, or extracted from natural resources like ore or timber. The problem with that approach is it creates a lot of waste. A leaf isn't cut out of a roll of green stuff.
Strides are already being made toward greener 3-D printing, as some of the printers use a corn-based polymer called polylactic acid (PLA). That's a start, said Benyus, but there's still a long way to go.
"PLA is biodegradable, but I wouldn't want us growing genetically engineered corn, with huge inputs of fossil fuels and fertilizers, to grow plastics. That's the old industrial model," she said. "I would rather have us use waste streams, ideally locally sourced ones, or become more plantlike and use excess carbon dioxide to make polymers, instead of asking plants to make them for us."
Benyus said scientists at the University of California, Berkeley, are looking at using waste sawdust in 3-D printers. Other ideas include using chicken feathers or waste from seafood processing. She pointed to a company called Novomer, which is working on making polycarbonates from smokestack emissions catalyzed by citrus oil.
To Benyus, the end of a printed product's life cycle is also critical. "Let's build an ecosystem of companies that take back the products," she said. "If they are biologically sourced get them back to the soil; if they are technically sourced get them back to the printer."
Taking the products apart should be easy, she said, given the way nature has bacteria and enzymes ready to devour or deconstruct anything that stops moving.
Markus J. Buehler, a professor and head of the department of civil and environmental engineering at MIT, told National Geographic that the idea of using biomimicry to inform 3-D printing design is "very positive, and may be critical to advance the technology to the next level." He said it could eventually lead to higher efficiency and lower prices, as well as lower environmental impact.
Buehler said it would be great to use natural, safe materials to build things, the way a tree grows or a spider produces silk. But the problem is that "we don't really understand how to do that." He said a lot of biology and chemistry needs to be worked out in order to produce our own materials from these simple building blocks, but progress is being made.
"We are in a time when these two technologies are emerging, when we now have 3-D printers that can print with microscale resolution to create objects with virtually any pattern and any shape," he noted. Meanwhile, "scientists are starting to understand how nature makes things at the smaller scales, based on the self-assembly of molecules like proteins or sugars to create functional materials."
Nanotechnology will take that to the next level, and will soon show up in 3-D printers, he predicts.
To Benyus, one of the lessons of biomimicry is the model of distributed growth and production. "An oak tree makes lots of leaves to catch the sun, not one big leaf," she said.
With 3-D printing, everyone can become their own manufacturer. They'll be able to make small items at home, and if they need something larger or more complicated, they could use the neighborhood printer, or maybe one at a local store. "Designs will crisscross the globe, instead of products," said Benyus, and this would obviously produce savings in both shipping costs and associated emissions.
But she also ponders the potential downsides: What happens to consumption patterns if we can make whatever we want, whenever we want? Will we throw more things away or fewer, because we had a hand in their manufacture?
The next step is opening a dialogue with the design community, engineers, entrepreneurs, and the public, said Benyus. She will also be conducting research and working on a library of biomimetic functions that anyone can utilize.
"We have an opportunity to reshape this new manufacturing revolution in another image," she said.
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