Materials and engineering: Rebuilding the world

Journal name:
Nature
Volume:
545,
Pages:
S15–S20
Date published:
DOI:
doi:10.1038/545S15a
Published online

Scientists commercializing technologies that enable sturdier and more-sustainable structures.

Mosaic Materials: Capitalizing on carbon capture

University of California, Berkeley

Chemist Zoey Herm fills a balloon with carbon dioxide using a bike-tyre cartridge, then fits it over the lip of a bottle of chalky white pellets. While she chats with fellow chemist Thomas McDonald, co-founder and chief executive of start-up Mosaic Materials, the bottle becomes warm to the touch, releasing heat as the porous materials inside absorb the CO2.

A time-lapse video of the demo is striking: in 20 minutes the balloon completely deflates as the gas is absorbed by the pellets. These materials absorb more CO2, and release it more readily, than existing CO2 separation materials. McDonald and Herm hope that the technology can lower the cost of carbon-capture systems for fossil-fuel power plants.

Their demo, at the company's space at the Lawrence Berkeley National Laboratory in California, shows both the potential of Mosaic's technology, and how much remains to be done before the company, which was founded in 2014, can make commercial-scale systems.

“The materials have a long way to go,” says McDonald, who developed the substance as a graduate student at the University of California, Berkeley. He and Herm are working on methods to manufacture large quantities of the pellets, and designs for the reactor systems that will use them. “From a young age, the CO2 problem has driven me,” McDonald says. “If we can make this work, it has a lot of promise to act as a bridge to a lower-carbon future.”

Chain reaction

Currently, carbon is captured by bubbling power-plant flue gas through solutions of amine compounds. Once the carbon has been absorbed, the solution is heated to around 120–150°C to release the gas. The steam is diverted from power-plant production, but this reduces output by about 30%, says chemist Jeffrey Long, who was McDonald's PhD adviser and is a Mosaic co-founder. “We wanted to develop materials to allow us to do this without the big energy penalty,” he says.

Herm's small bottle has a vast surface area to capture CO2. The pellets inside are made of metal–organic frameworks (MOFs). These highly porous materials are made up of crystalline, repeating units of metal clusters held together by organic-molecule linkers. By tinkering with the chemistry of the linkers, researchers can control the size of the pores in a MOF and their chemical activity.

Marilyn Chung/Lawrence Berkeley National Laboratory

Thomas McDonald and Zoey Herm demonstrate the CO2 absorption properties of their pellets.

The Berkeley group's MOFs have linkers that contain amine groups — similar to the groups present in the conventional aqueous capture process. The researchers expected the MOFs to separate CO2, but they were surprised by how much of the gas was absorbed, and how easy it was to control its subsequent release from the material. Once one CO2 molecule is absorbed, others follow. “It's a chain reaction,” says Long.

The Berkeley MOFs also operate in a more-modest temperature range than conventional carbon-capture materials. The MOFs absorb CO2 at 35°C and release it rapidly when the temperature rises by about 45°C — low enough for the release to be triggered by heat from power-plant waste steam. In the best-case scenario, the MOF system could capture and sequester the greenhouse gas for little to no cost.

Still, admits Long, “there is not much of a business reason to do this.” In the absence of strict regulations — an approach that seems to have lost political steam at the federal level in the United States, with the administration of President Donald Trump scrapping Barack Obama's plans to cap CO2 emissions — power plants are not looking to make significant investments in carbon capture. And for now, Mosaic is not focusing on the power-plant market.

The company currently has a grant from the US Navy to develop an air-filtration system for submarines. MOFs would provide a less-pungent alternative to amine filtration systems. And Mosaic is pursuing industrial uses that involve the energy-intensive amine-solution technique. The concentration of CO2 in natural gas, for example, must not exceed 2% for the fuel to be added to pipelines, and CO2 must be separated from hydrogen before it can be used as a fertilizer feedstock. Other types of gas separation licensed by Mosaic Materials from the University of California, Berkeley, could also prove valuable. One of the company's MOFs, for instance, can separate out undesirable hydrocarbons from petrol, leaving behind only the valuable high-octane molecules.

Escaping the valley of death

Even with a promising technology, a few articles in high-profile journals and a clear sense of the market, it's difficult for a materials start-up to find its footing. Venture capitalists would often rather invest in software companies that are more likely to make a quick return than risk millions of dollars and years in new technologies that may flop. “With anything coming out of a fundamental research lab,” says Long, “there's a huge amount of risk.”

“For every application we tackle, we're learning how to scale up.”

And Mosaic does not have the field entirely to itself. Academics have been researching MOFs for decades, and the compounds have been the object of industrial interest since the late 1990s, when chemists began making them durable. NuMat Technologies in Skokie, Illinois, which emerged from Northwestern University in Evanston, Illinois, in 2011, makes canisters for storing toxic gases used by the electronics industry. The company launched their first product last September. The gases sit inside the pores of MOFs, and the canisters don't need to be pressurized. This is safer, says Omar Farha, chief scientific officer at NuMat — if the canister is punctured, the gas won't leak out. “For every application we tackle, we're learning how to scale up, and how to form the MOFs,” says Farha.

Mosaic is part of a US Department of Energy start-up incubator called Cyclotron Road that is designed to support materials and energy companies during the transition from academic project to commercial product or service. “If a technology is too mature for an academic environment, but not ripe for investment,” says McDonald, it can enter a kind of valley of death. Cyclotron Road shepherds start-ups through that treacherous interlude by providing mentors, lab space, funding and access to expensive equipment. Mosaic Materials is among the first dozen start-ups to benefit from Cyclotron Road.

Walking through the company's lab space, McDonald explains that although the balloon trick makes for a good demonstration, it is not a very precise way to measure how much CO2 the materials can absorb. To test new formulations of their MOFs, Mosaic chemists use the volumetric gas absorption analysers at Lawrence Berkeley. They have also taken advantage of the lab's imaging equipment and other expensive apparatus that are beyond the reach of a typical start-up. These measurements have helped the company to maintain the quality of its MOFs as it scales up from production in 1-litre vessels to 100-litre reactors.

Even with these resources available to them, Herm and McDonald have had to be creative. One challenge was working out how to compress their MOF powders into pellet form, so that the compound would not blow away in the gas stream. A meat grinder in the lab is evidence of one bad idea they had about how to do it, says Herm. The large tablet press beside it, a piece of equipment typically used by homeopaths, worked much better.

Last September, Mosaic secured private investment from clean-technology fund Evok Innovations in Vancouver, Canada. The company is growing, and McDonald is looking to hire four more people, as well as find the firm a new location for when their time in the Cyclotron Road incubator ends later this year. Long is confident about the company's prospects: McDonald “discovered this amazing material, he knows more about it than anyone else, and he's excited to see it happen in the real world”.

Basilisk: Building, heal thyself

Delft University of Technology, Netherlands

What if the concrete walls of tunnels, buildings and bridges were more like living tissue, able to heal their own wounds?

Henk Jonkers thinks that this vision will one day be a reality. Jonkers, a civil engineer at Delft University of Technology in the Netherlands, is the founder of Basilisk, a company that manufactures an additive that makes concrete self-healing.

De Beeldredaktie/www.beeldredaktie.nl

Basilisk makes an additive that helps concrete to 'self-heal'.

Water is the real enemy of structural concrete, he says, because it corrodes the steel reinforcing bar that supports the material. “We were looking for a mechanism that would become active at the moment concrete cracks and water begins to penetrate those cracks.”

He needed something that would remain stable in the concrete for decades, but react when exposed to water. It also had to withstand the alkaline environment found in most concrete. In pursuit of this ingredient, he and his colleagues collected samples from highly alkaline soda lakes in Siberia, Africa and northern Spain, as well as bacteria that live in rocks. Eventually, they found what they were looking for — a species of Bacillus that survives for long periods in the form of spores, but that reawakens when exposed to water. Jonkers infuses cement — an ingredient of concrete — with the spores and an inert additive, calcium lactate. When revived, the bacteria devour the calcium lactate and secrete calcium carbonate, or limestone, which fills the cracks and prevents water from reaching the reinforcement bar. Jonkers estimates that the additive can increase the lifetime of the concrete by 20–30%.

In a cubic metre of concrete that contains 15 kilograms of his mixture, the density of bacteria allows cracks of up to one millimetre wide to be sealed. By including that proportion of mixture, “you double the price of the concrete mix,” Jonkers says. But he points out that the price of concrete is about 1% of the overall cost of building a bridge, and the additive should lead to savings in repair and maintenance.

The company is also developing a self-healing mortar, and a liquid that can be used to patch cracks in structures built without Jonkers's self-healing concrete. Jonkers hopes that positive experiences with these products will increase the concrete industry's willingness to include the self-healing additive in their new concrete. Basilisk has distributors in Japan, Germany and Belgium, and in 2016 launched an operation in South Korea to manufacture the additive.

Jonkers founded Basilisk with support from Delft's Valorisation Centre, which handled the patenting and provided an initial loan. The university's involvement not only helped Jonkers form Basilisk, but also furthered the university's interests. “They want to make a profit on it,” Jonkers says, “but they also want the technologies that we develop at the university to somehow make their way into society.”

Carbicrete: Steel in, carbon out

McGill University, Montreal, Canada

When it comes to making the building trade more environmentally friendly, Mehrdad Mahoutian is hoping to kill two birds with one concrete block.

Civil engineer Mahoutian is the founder of Carbicrete in Montreal, Canada. The company hopes to create carbon-negative concrete blocks; the aim is to not only eliminate carbon dioxide waste from the production process, but also to capture and store extra CO2. “It's cheaper, it's greener, and has the same properties or even better properties than cement blocks,” Mahoutian says.

Concrete production is a big emitter of greenhouse gases. The main culprit is Portland cement — a key ingredient of construction concrete that holds together the mix of sand, gravel and crushed stone. For each tonne of Portland cement produced, roughly a tonne of CO2 is spewed into the atmosphere, trapping heat and contributing to climate change. Concrete is the basis for many buildings, from skyscrapers to bridges, and about 4.6 billion tonnes of cement are produced annually. Concrete production is responsible for about 5% of annual man-made carbon emissions worldwide, according to the World Business Council for Sustainable Development.

When Mahoutian started his PhD in civil engineering at McGill University in Montreal in 2011, his goal was to find a material that would sequester carbon, trapping it before it could get into the atmosphere. Instead, he came up with a new recipe for making concrete.

“We totally get rid of cement,” he says. “Instead we use slag, the waste material of steel-producing plants.” The slag is calcium silicate. When wet calcium silicate is injected with CO2 gas, calcium carbonate, or limestone, forms. Limestone and the aggregate form Carbicrete.

A typical concrete block used in construction weighs about 17 kilograms, of which 2 kg is cement. Because the CO2 produced by processing slag is negligible, a Carbicrete block reduces CO2 emissions by 2 kg, he says. Added to the kilogram of CO2 injected to produce the limestone, a single block flips the carbon footprint from a release of 2 kg to an absorption of 1 kg.

The new material has roughly 50% greater compressive strength than conventional concrete, Mahoutian says, and resists moisture about equally. And because slag costs roughly US$5 a tonne, compared with $100–110 for cement, the final product should be about 20% less expensive. In Canada, it is even more financially attractive: the national carbon tax will begin next year at Can$10 per tonne and rise to Can$50 per tonne by 2022.

Carbicrete's potential to remove a huge source of carbon emissions earned it a spot as one of 27 semi-finalists for the NRG Cosia Carbon XPrize, which will award US$20 million to one or two teams that can convert CO2 from coal- and gas-powered plants into useful products. The contenders must now build demonstration facilities to show off their technologies and will be further whittled down to ten by early 2018, with the winners announced in 2020. “To be able to link the waste of one industry and have it feed into another industry is huge,” says Marcius Extavour, technical director of the prize.

While Mahoutian was working on the technology at McGill, he had assumed that he would stay in academia. But after he told the university's technology licensing office about his invention, McGill officials filed for patents, and presented his and several other technologies to Christopher Stern, a local entrepreneur who was looking for green technologies to invest in. Stern selected Carbicrete, and met with Mahoutian weekly for about six months to help him with the many facets of starting a company. “I'm a technical guy, so for me it was difficult to write a business plan,” Mahoutian says.

Although the McGill Dobson Centre for Entrepreneurship offers mentorship and legal services, Mahoutian says he did not turn to those services very much. Most of what he learned came from Stern, who is now Carbicrete's chief executive. But the company did win Can$10,000 last year in a competition run by the centre that recognizes promising start-ups.

Eventually, Carbicrete plans to license its technology and sell concrete producers its slag-based material, but not go into concrete production itself. As a step towards that goal, the company is raising funds to build a pilot plant that Mahoutian hopes will produce 1,000 blocks a day by the end of 2017. For now, Carbicrete relies on grants from the government through Sustainable Development Technology Canada and Canada's Industrial Research Assistance Program.

Extavour expects companies to take up what Carbicrete is offering. “Their pitch is 'I will save you money. I will reduce your emissions and I will feed those back into your product,'” he says. “That's a compelling argument.”

Slips Technologies: Sliding away

Harvard University, Cambridge, Massachusetts

The lotus leaf has long inspired scientists who create non-stick coatings. The leaf, which conjures up images of beauty and serenity, has a hydrophobic surface that repels water and dirt. But biomaterials specialist Joanna Aizenberg was inspired by a decidedly less poetic natural surface — the human gut.

“All these ugly, nasty things that go through us are never in contact with the walls of our intestines,” says Aizenberg, at Harvard University. Aizenberg founded SLIPS Technologies; SLIPS stands for slippery, liquid-infused porous surfaces, which neatly sums up the company's core technology.

Vpro.nl/Themindenglish

Specially developed paints help to deter marine fouling in field trials.

The reason that nothing sticks to the intestine is that it has a rough surface covered by a slippery mucus, which prevents bacteria and food particles from gaining a foothold. The same idea underpins Aizenberg's coating technology: the structure of a surface is designed to trap a liquid lubricant, and anything that comes into contact with the lubricant will slide off. The details vary depending on the surface — the steel hull of a ship might have a bumpy coating painted on before the lubricant is added, whereas a plastic might be altered chemically to get the liquid to adhere — but the effect is the same.

With a grant from the US Advanced Research Projects Agency — Energy (ARPA-E), her lab examined the potential energy savings of applying the coating to everything from naval vessels to household freezers. The lab estimates that coating the coils of every refrigerator and freezer in the United States to prevent the build-up of ice would reduce energy use by five terawatt-hours per year, saving consumers about US$500 million annually. Coating the hull of every commercial ship in the world to prevent marine organisms attaching and causing drag would save an estimated 586 terawatt-hours and result in annual savings of $10 billion to $20 billion. The first products the company is developing include marine paints, coatings for industrial equipment such as mixing blades and bioreactor tanks to make cleaning easier, and food containers with surfaces that mean ketchup won't stick in the bottle. SLIPS co-founder and chief technology officer Philseok Kim says the first commercial products should appear by early 2018.

Aizenberg turned to Harvard's Wyss Institute for Biologically Inspired Engineering, which has an emphasis on commercializing discoveries, to develop the technology so that it was ready for licensing. One early investor was the German chemical giant BASF, which invested $1.5 million in the fledgling company and signed a joint development agreement. Aizenberg saw that as a major vote of confidence. The institute's founder, Hansjörg Wyss, also supplied $1.5 million. The US Department of Energy supported the company with a $5 million grant last December. But SLIPS may prove to be one of the last companies to get its start in this way — US President Donald Trump's administration has proposed eliminating all funding for ARPA-E.

Kinetica Dynamics: Skyscraper stabilizer

University of Toronto, Canada

Kinetica Dynamics may be a young start-up, but its approach to stabilizing tall buildings is based on a well-established idea.“It's a reinvigoration of an old vibration damping technology,” says Michael Montgomery, an engineer and the company's co-founder and chief executive.

The technology, a polymer that diminishes vibration and shock, is bonded tightly to the structure of buildings and was first used in the twin towers of New York's World Trade Center to prevent motion sickness caused by the upper parts of the towers moving in the wind. The polymer, which was created by the US technology company 3M, was installed between the steel frames throughout the towers to dissipate vibrations.

Kinetica

Co-founder Michael Montgomery shows examples of the dampers developed by Kinetica.

In the past few decades, however, high-rise buildings have been built mostly out of concrete. The 3M polymer isn't as efficient with this construction method. Instead, wind-damping systems in these skyscrapers usually involve huge tanks of water or steel pendulums at the top of the building. But these systems occupy a lot of space and cannot efficiently be used to reduce seismic vibrations or the damage they cause.

By placing large dampers at locations between concrete structures where the stresses from vibrations are the highest, Kinetica has adapted the original distributed system to work efficiently in concrete buildings.

“If we didn't step up and develop it, we knew it would go by the wayside.”

Montgomery's PhD supervisor, Constantin Christopoulos, a civil engineer at the University of Toronto in Canada, and his colleagues devised the system in 2004. Suspecting that unless they took on the commercial challenge themselves, the idea would never make it out of academic journals, Montgomery and Christopoulos launched the company in 2011.“If we didn't step up and develop it, we knew it would go by the wayside,” says Montgomery.

The biggest challenge, says Montgomery, is getting the risk-averse construction industry to take a chance on a start-up with an unconventional idea. “They're happy to be second, but scared to be first,” he says. “They want to work with people who have done it before.”

Kinetica has partnered with 3M and Japanese manufacturing company Nippon Steel and Sumitomo Metal. These big companies can help Kinetica to get a seat at the table to pitch its technique. They also manufacture the product, whereas Kinetica handles the design. Kinetica also now pitches itself as a company that uses a damper that has a long and successful history in steel buildings, rather than as a young start-up with a new idea.

The slow pace of large-building construction is another challenge for Kinetica. “We're a small company dealing with timelines of 5 to 7 years,” says Montgomery. “That's a pretty long time to stay afloat before the device actually gets into a building.

The company takes on consulting jobs to bridge the gap, but its founders hope that Kinetica is about to take off. The first building to use its damping system is currently under construction in Toronto, with the dampers set to be installed in the next six months. Another five buildings are in various stages of design.

8Power: Vibration power

University of Cambridge, UK

Imagine a pendulum like a yo-yo moving a magnet through a coil, and generating a current. This is how Antony Rix, chief executive of 8power, explains an innovative way to harvest vibration energy using a phenomenon known as parametric resonance. Conventional methods for vibration harvesting effectively move the anchor point from side to side, causing the pendulum to resonate; 8power's innovation, which was developed at the University of Cambridge, UK, also moves it up and down, amplifying the swing. “The increase in energy harvesting is about tenfold,” says Rix. “We are the first people to get parametric resonance to work for energy harvesting.”

Initially, the company is using the technology to continuously power vibration sensors with the energy of the vibrations the devices are designed to detect. The technology has been piloted on the Forth Road Bridge, which connects Edinburgh and Fife in the United Kingdom and was closed in 2015 for several weeks owing to a structural defect found during routine inspections. 8power suggests that its vibration sensor might have detected this problem much sooner, and perhaps avoided the need to close the bridge.

SteveAllenPhoto/ Getty

8power's device was tested on the Forth Road Bridge.

Rix co-founded 8power in 2016, along with four researchers who worked on the technology while at the University of Cambridge. Most of the company's funding comes from Cambridge Enterprise, the university's commercialization arm, and the intellectual-property commercialization company IP Group. With a background in research commercialization and product development, Rix has first-hand experience of the tensions that often emerge when setting up a university spin-off. Generally speaking, investors such as Rix try to negotiate maximum control over intellectual property, while universities aim to retain as much as possible. In 8power's case, intellectual property stayed with the university, who license the right to commercialize it to the company. “It wasn't a straightforward process,” says Rix.

The company is now showcasing its prototype sensor at US and European trade fairs. It is not just the condition of bridges that the technology can be used for, it is also being targeted at companies who need to monitor the condition of industrial machines. And in the longer term, various sensors could be powered indefinitely anywhere there is sufficient vibration energy to be harvested. The company also has a miniaturized, 12-millimetre-square chip version, and is planning to sell its first products later this year.

Voxel8: 3D printing mixes materials

Harvard University in Cambridge, Massachusetts, and the University of Illinois at Urbana-Champaign

The machine sitting on the counter of a lab in Massachusetts is the size and shape of an ordinary desktop printer, but it looks like it has been crossed with a juke box. There's no place for paper, and the moving arm beneath the transparent orange cover doesn't pluck out a record for the turntable. Instead, it contains a pair of dispensing heads: one that extrudes a thin layer of thermoplastic from a spool, and another that deposits silver that will become a conductive wire. Both heads move back and forth across a plate and slowly build up a 3D object, layer by layer.

Lori K. Sanders, Voxel8 Inc.

A 3D printer combines multiple materials to create structures such as this piece for athletics shoes.

This 3D printer is one of the first products of Voxel8, a start-up that is developing systems to allow the manufacture of a variety of items made of multiple materials. Most 3D printing so far has been devoted to rapid prototyping — making models of products that will eventually be built with more established manufacturing processes — and has been limited to one material at a time, or a couple of very similar materials.

Voxel8, however, is developing an assortment of polyurethane, silicone, plastic, epoxy and silver inks for printing at room temperature, with the aim of making parts and products that are ready for real-world use. “Printing multiple materials together is very new,” says Philippe Inagaki, chief executive of Voxel8. “You start opening up new materials and mixing them together, suddenly you can do much more.

Voxel8 has engineered various inks, which start fairly solid, but flow through a nozzle like liquid when force is applied and solidify once they've exited and the force is gone. Applying a chemical or ultraviolet light makes the shape permanent. All this can be done at room temperature; previous printers couldn't easily mix materials such as metals and plastic because the heat needed to fuse the metal together would burn away the plastic.

One of the first items the company created with the technology was a small antenna that could cover a wide frequency range and replace larger dish antennas. MITRE, a non-profit engineering firm in Bedford, Massachusetts, had designed such an antenna for a US government agency, but had no way to build it. That is until a representative of MITRE met the Voxel8 team through a competition in Boston, Massachusetts, run by the start-up accelerator MassChallenge.

The technology allowed MITRE to build a silver conductor inside a polymer array, with tiny structures that provided the antenna with the necessary wideband performance. Voxel8, meanwhile, won US$50,000 from the contest.

The printer could also be used for consumer products such as athletics shoes. The shoes consist of a variety of materials with varying combinations of stiffness and softness, and their manufacture can't be easily automated, Inagaki says. But with a digital scan of a foot, multimaterial 3D printing could make a customized shoe that fits perfectly. And the same could be true of medical devices, such as a sleep-apnoea mask that is tailored to an individual's face. The mask transitions from a soft material at the point of skin contact to a hard one where it attaches to the machine. Customized stents or orthotics might also benefit from the technology.

Voxel8 was founded by Jennifer Lewis, a materials engineer and associate director of the Materials Research Science and Engineering Center at Harvard University in Cambridge, Massachusetts, along with three of her students, who now have positions in the company. She had started talking to venture capitalists about the technology while working at the University of Illinois at Urbana–Champaign, but put that on hold while she moved to Harvard. The company has licensed patents from both Harvard and Illinois.

Both universities were helpful in launching the firm, Lewis says. Harvard's Office of Technology Development provided funds to hire a software developer to create the programs to control the printing process. Voxel8 has a space at Greentown Labs, a clean-technology incubator in Somerville, Massachusetts, for companies that are intending to use less energy or produce less waste than the processes they're trying to replace. “This rent here is probably a tenth of what you'd pay in Kendall Square,” says Lewis, referring to the area close to Massachusetts Institute of Technology that's been home to many biotech start-ups over the past few years. Being part of Greentown Labs also gives the company access to software such as SolidWorks, a computer-aided design and simulation program that, at thousands of dollars a year per licence, would otherwise be out of the company's budget, says Travis Busbee, a former postdoctoral student in Lewis's lab who now heads materials development at Voxel8.

So far, Voxel8 has sold the printer to more than 100 researchers and companies, who will provide feedback on how well it works and what they'd like to be able to do with it. Based on their responses, Voxel8 will choose segments of industry to focus on, and develop the materials and processes necessary to make particular products. Inagaki projects that the technology could start being used for mass production in about three years.

Lewis sees herself mainly as an academic, and conflict-of-interest rules dictate that there must be a separation between her lab's work and the company, where she is a scientific advisor. But writing academic papers isn't always the best way to get an innovation out into the world, she says. “There is this gulf,” Lewis says, “and to bridge it I think start-ups are playing an incredibly important role.”

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  1. Katherine Bourzac is a freelance journalist in San Francisco, California.

  2. Neil Savage is a science and technology writer in Lowell, Massachusetts.

  3. Brian Owens is a freelance journalist based in New Brunswick, Canada.

  4. Andrew R. Scott is a science writer in Perth, UK.

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