While hydrogen-powered cars might seem to be in the far-off future, it might not take as long as previously thought for hydrogen-cell cars to be a viable option. A team of researchers including scientists at the National Institute of Standards and Technology (NIST; Gaithersburg, MD) may have overcome a significant hurdle to manufacturing hydrogen fuel cells by creating a way to check whether the expensive catalysts that the cells need have been incorporated quickly and effectively.
Improved measurement methods are key to bringing hydrogen power a step closer to economical mass production. Hydrogen vehicles currently have not emerged as an option like the latest electric models, but it’s not for lack of efficiency or environmental friendliness, NIST noted. Hydrogen gas contains about three times as much energy by mass as fossil fuels do, and a fuel cell’s only byproduct is water.
Although filling a fuel tank with hydrogen is fast, building the engine is not, at least by industrial standards. A fuel cell requires thin layers of a platinum-based catalyst to convert hydrogen into electric energy, and the industry has lacked an efficient way to evaluate the layers’ properties. That’s one reason why only about 1800 hydrogen vehicles were on the road as of a year or so ago, the NIST researchers noted, and they can cost twice as much as a conventional vehicle.
The catalyst needs to end up as two thin layers on either side of a polymer sheet that resembles plastic wrap, so the industry’s approach has been to treat the catalyst like ink. The process mixes platinum particles with carbon to form a deep black fluid that even looks ink-like. Then a machine resembling a newspaper printing press lays the mixture down as the sheet unspools from a giant roll. The problem is that the platinum in this ink costs upwards of $35 per gram ($1000 an ounce), so manufacturers need a way to make sure just enough is laid down to get the job done—and not one costly drop more. And the process has to be fast enough to make fuel cells for thousands of cars per year, meaning the plastic has to roll quickly.
The team, which included scientists from NIST and industry, found an answer stemming from their experience measuring small objects for a completely different industry: computer chip manufacturing. But their approach, which is based on reflecting a laser’s light from a chip surface, demanded some revisions.
“We’ve got expertise in optical methods for measuring features smaller than 10 nanometers on chips, and the platinum particles are at the same scale,” said NIST physical scientist Michael Stocker. “We knew basically what we were doing, but chips don’t fly by at 30 meters (about 100 feet) per minute, so there was a speed challenge. Plus, you’re looking at something that’s black, so we didn’t have much reflected light to measure.”
After addressing this challenge through research and development, the team built a novel instrument using off-the-shelf technology that can detect the low levels of light reflected off the tiny platinum particles as the sheet moves past at a meter or two per minute. Stocker said there are no fundamental barriers to scaling up the method or increasing the speed to meet the industry’s future needs. For instance, a manufacturer could array a row of these instruments to scan a meter-wide sheet, with each one identifying trouble spots in a particular section. Though the method would likely need to be combined with other techniques such as X-ray fluorescence to form a complete solution, Stocker said that it leaves fuel cell manufacturers in a good place. “It’s all just optical engineering from this point onward,” he said. “Industry can take it from here.”
The scientists’ research was recently published online in the Journal of Power Sources in a paper entitled, “Development of large aperture projection scatterometry for catalyst loading evaluation in proton exchange membrane fuel cells.” For an abstract, see 10.1016/j.jpowsour.2017.07.092.
Researchers Find Bacteria Self-Organize to Build Working Sensors
Researchers at Duke University (Durham, NC) have turned bacteria into the builders of useful devices by programming them with a synthetic gene circuit.
As a bacterial colony grows into the shape of a hemisphere, the gene circuit triggers the production of a type of protein to distribute within the colony that can recruit inorganic materials. When supplied with gold nanoparticles by researchers, the system forms a golden shell around the bacterial colony, the size and shape of which can be controlled by altering the growth environment. The result is a device that can be used as a pressure sensor, proving that the process can create working devices.
While other experiments have successfully grown materials using bacterial processes, they have relied entirely on externally controlling where the bacteria grow and have been limited to two dimensions. In the new study, the Duke researchers demonstrate the production of a composite structure by programming the cells themselves and controlling their access to nutrients, but still leaving the bacteria free to grow in three dimensions.
The study appears in Nature Biotechnology in a paper, “Programmed Assembly of Pressure Sensors Using Pattern-Forming Bacteria,” by Yangxiaolu Cao, Yaying Feng, Marc D. Ryser, Kui Zhu, Gregory Herschlag, Changyong Cao, Katherine Marusak, Stefan Zauscher, and Lingchong You.
“This technology allows us to grow a functional device from a single cell,” said Lingchong You, the Paul Ruffin Scarborough Associate Professor of Engineering at Duke. “Fundamentally, it is no different from programming a cell to grow an entire tree.”
Nature is full of examples of life combining organic and inorganic compounds to make better materials, the scientists noted. Mollusks grow shells consisting of calcium carbonate interlaced with a small amount of organic components, resulting in a microstructure three times tougher than calcium carbonate alone. Our own bones are a mix of organic collagen and inorganic minerals made up of various salts.
Harnessing such construction abilities in bacteria would have many advantages over current manufacturing processes. In nature, biological fabrication uses raw materials and energy very efficiently. In this synthetic system, for example, tweaking growth instructions to create different shapes and patterns could theoretically be much cheaper and faster than casting the new dies or molds needed for traditional manufacturing.
“Nature is a master of fabricating structured materials consisting of living and non-living components,” said You. “But it is extraordinarily difficult to program nature to create self-organized patterns. This work, however, is a proof-of-principal that it is not impossible.” The researchers were able to alter the size and shape of the dome by controlling the properties of the porous membrane it grows on. Changing the size of the pores or how much the membrane repels water affects how many nutrients are passed to the cells, altering their growth pattern.
“We’re demonstrating one way of fabricating a 3D structure based entirely on the principal of self-organization,” said Stefan Zauscher, the Sternberg Family Professor of Mechanical Engineering & Materials Science at Duke. “That 3D structure is then used as a scaffold to generate a device with well-defined physical properties. This approach is inspired by nature, and because nature doesn’t do this on its own, we’ve manipulated nature to do it for us.”
To show how their system could be used to manufacture working devices, the researchers used these hybrid organic/inorganic structures as pressure sensors. Identical arrays of domes were grown on two substrate surfaces. The two substrates were then sandwiched together so that each dome was positioned directly across from its counterpart on the other substrate.
“In this experiment we’re primarily focused on the pressure sensors, but the number of directions this could be taken in is vast,” said Yangxiaolu Cao, postdoctoral associate in You’s lab and first author of the paper. “We could use biologically responsive materials to create living circuits. Or if we could keep the bacteria alive, you could imagine making materials that could heal themselves and respond to environmental changes.”
“Another aspect we’re interested in pursuing is how to generate much more complex patterns,” said You. “Bacteria can create complex branching patterns, we just don’t know how to make them do that ourselves—yet.”
The study was supported by the Office of Naval Research, the National Science Foundation, the Army Research Office, the National Institutes of Health, the Swiss National Science Foundation, and a David and Lucile Packard Fellowship.
Titomic Issues $6.5M Stock Offering
Additive manufacturing specialist Titomic Ltd. (Melbourne, Australia) said it will list on the Australian Securities Exchange (ASX: TTT) after raising $6.5 million via a fully underwritten initial public offering (IPO).
Titomic was established to deliver industrial-scale manufacturing using its proprietary Kinetic Fusion process and enable companies to leverage advanced materials. Titomic Chairman Philip Vafiadis said the company is building one of the largest metal additive manufacturing machines in the world at its facility in Melbourne. “At 40.5-cubic-meters build area, Titomic will house one of the world’s largest metal additive manufacturing machines, with commercial production speeds of up to 45 kg per hour,” Vafiadis said.
Titomic worked with CSIRO (Commonwealth Scientific and Industrial Research Organization) in Australia to develop a technology that applies cold-gas dynamic spraying of titanium or titanium alloy particles onto a scaffold to produce a load-bearing structure. The company has exclusive rights to commercialize the proprietary and patented process.
The funds from IPO will enable Titomic to complete commissioning of the Melbourne facility, co-develop parts production with clients and build sales capacity of Titomic systems. The company will issue 32.5 million shares at a price of $0.20/share under the IPO, giving the company a market capitalization of approximately $22.6 million upon listing. It expected to commence trading under the code TTT on September 21, 2017.
TechFront is edited by Senior Editor Patrick Waurzyniak; firstname.lastname@example.org.