CU Boulder’s   played a key role in studying tiny bioglass lenses that were designed to form on the surface of engineered microbes, a scientific breakthrough that could pave the way for groundbreaking imaging technologies in both medical and commercial applications.

The project, led by the University of Rochester and published in Proceedings of the National Academy of Sciences, was inspired by the enzymes secreted by sea sponges that help them grow glass-like silica shells. The shells are lightweight, durable and enable the sea sponges to thrive in harsh marine environments.

“By engineering microbes to display these same enzymes, our collaborators were able to form glass on the cell surface, which turned the cells into living microlenses,” said Wil Srubar, a coauthor of the paper and professor of Civil, Environmental and Architectural Engineering and the Materials Science and Engineering Program. “This is a terrific example of how learning and applying nature’s design principles can enable the production of advanced materials.”

Professor Wil Srubar

Using imaging and X-ray techniques, CU Boulder researchers analyzed the silica, also known as “bioglass,” and quantified the amount surrounding different bacterial strains. The CU Boulder researchers demonstrated that bacteria engineered to form bioglass spheres contained significantly higher silica levels than non-engineered strains. Combined with optics data, the results confirmed that bacteria could be bioengineered to create bioglass microlenses with excellent light-focusing properties.

Microlenses are very small lenses that are only a few micrometers in size—about the size of a single human cell and designed to capture and focus or manipulate light into intense beams at a microscopic scale.  Because of their small size, microlenses are typically difficult to create, requiring complex, expensive machinery and extreme temperatures or pressures to shape them accurately and achieve the desired optical effects.

The small size of the bacterial microlenses makes them ideal for creating high-resolution image sensors, particularly biomedical imaging, allowing sharper visualization of subcellular features like protein complexes. In materials science, these microlenses can capture detailed images of nanoscale materials and structures. In diagnostics, they provide clearer imaging of microscopic pathogens like viruses and bacteria, leading to more accurate identification and analysis.

The University of Rochester contributed to this report.

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Prometheus Materials eyes expansion through increased production 

Traditional cement production is responsible for about 7 percent of global greenhouse gas emissions, making it a significant contributor to climate change. 

So faculty at CU Boulder started developing a greener alternative. A Department of Defense-funded project launched in 2016 led to the creation of an eco-friendly cement with a minimal carbon footprint, emitting little to no carbon dioxide and recycling 95 percent of the water used in production. 

In 2021, they made the move to commercialize the technology as Prometheus Materials. Founded by Associate Professors Sherri Cook, Mija Hubler and Wil Srubar of civil, environmental and architectural engineering, along with Jeff Cameron of biochemistry and CEO Loren Burnett, the Colorado-based company produces bio-concrete from the biomineralization of blue-green algae in a natural process similar to that which creates sea shells and coral reefs. 

While initially focused on research and development, the company has since entered a commercialization phase, exploring the establishment of new facilities to transition from a single production line to multiple lines and to increase production, Hubler said.

“We’re in flux,” she said. “We’re dreaming bigger.”

Product development

Hubler said the “most exciting part” is that Prometheus Materials has successfully scaled production and launched a commercial product for the construction industry. 

Initially, the team focused on assessing structural performance, particularly compressive strength. That led to the development of their inaugural product — the ProZero Bio-Block Masonry unit.

After constructing a pilot wall, the researchers put their ears to it and were met with a remarkable silence. Further tests confirmed the product’s efficacy in preventing sound from bouncing off or attenuating through walls. This discovery paved the way for another product, ProZero Sound Attenuation units. Potential uses include sound panels in large conference rooms and classrooms. 

The researchers also evaluated the product’s suitability for pedestrian and parking surfaces, analyzing its response to environmental moisture. The outcomes were positive, prompting the development of a third product.

Proof points

Mija Hubler with the Prometheus algae-growing system.

But consumers can’t yet walk into a hardware store and buy a ProZero product off the shelf.

While Prometheus Materials has performed some pilot studies with large companies like Microsoft and has discussed potential applications for its products in Microsoft’s offices and warehouses, it will take years before the products will be available in places like Home Depot.

Hubler emphasized that the construction industry prefers “tried and true” materials and is cautious to adopt new ones. Larger construction firms play a crucial role in pioneering and embracing innovative products, serving as trailblazers to introduce these newer products into the market. 

But there are multiple reasons why it’s the right time for the company to expand operations. 

“The construction industry, building owners and developers are paying a lot more attention to carbon emissions, and our materials have reduced emissions,” Srubar said. “[Another] driver is the trend toward nature-based materials that don’t contain any ‘red list’ chemicals in them.”

Cook added that many companies have ambitious corporate sustainability goals but lack practical means to achieve them. Prometheus Materials provides a tangible avenue for these companies to start realizing their sustainability objectives.

Srubar echoed the strategic importance of working with these firms, whose teams of architects and engineers collaborate in designing and engineering structures using innovative materials.

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Wil Srubar, associate professor in civil, environmental and architectural engineering and the Materials Science and Engineering Program, has been named to the 2023 cohort of the Schmidt Science Polymath Program.

Srubar was chosen from more than 58 applicants who outlined research ideas in STEM fields that represent a substantive shift from their current portfolio.

“I am beyond humbled and grateful for being selected to receive the Schmidt Science Polymaths Award. It truly is a career-defining honor,” Srubar said. “The award not only provides financial support for my work, but also enables me to approach it with an unencumbered, creative freedom to pursue high-risk, high-reward ideas. It’s such an incredible opportunity.”

In Srubar’s , his team develops innovative building materials, including a concrete-like material made from algae that can self-heal and is more sustainable than traditional concrete manufacturing.

With this new grant, Srubar is looking to further redefine the boundaries of living architecture — both on Earth and beyond.

“I am specifically interested in species of photosynthetic algae and other multifunctional, symbiotic organisms and their abilities to help us define and establish new paradigms for next-generation living — and carbon sequestering — materials for terrestrial and extraterrestrial built environments,” he wrote in his proposal.

Srubar and the other “polymaths” will receive $500,000 a year for up to five years to help support their research.

"We are pleased to bring together a group of determined researchers, each pursuing new research directions to tackle pressing global challenges," said Stuart Feldman, chief scientist of Schmidt Futures. "From improving brain imaging and addressing gender bias in medical research, to developing sustainable construction materials and advancing regenerative agriculture, these Polymaths' interdisciplinary work is poised to drive transformative advancements in diverse fields.”

About the Polymath Program

The Polymath Program is designed to push the boundaries of scientific and disciplinary limits by promoting the exploration of fresh methodologies and approaches in STEM to unlock breakthroughs and expedite progress in scientific discoveries. In receiving this award, the cohort receives support as they boldly transition from their established fields and enter into new disciplines or methodologies, bringing with them their expertise to conduct pioneering research. Through this model, the Polymaths’ work plays a vital role in advancing knowledge, fostering innovation, and exploring emerging technologies to test unconventional theories.

About Schmidt Futures

Founded by Eric and Wendy Schmidt, is a philanthropic initiative that finds and connects talented people across fields, generations and geographies to harness their collective skills for public benefit.

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Forbes Magazine is highlighting major research conducted by CU Boulder faculty into green concrete.

Cement is a significant contributor to carbon emissions, responsible for about eight percent of global output.

Prometheus Materials, a company co-founded by Wil Srubar and Mija Hubler, professors in the Materials Science and Engineering program, is commercializing an algae-based form of concrete developed from research at CU Boulder.

This new concrete that can be grown in a laboratory and has significant potential to drastically reduce environmental pollution caused by construction activities around the globe.

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Associate Professor Wil Srubar has been nominated for the 2023

Srubar is part of the Department of Civil, Environmental and Architectural Engineering and the Material Science and Engineering Program at CU Boulder. His lab conducts major research into biomimetic and living materials that have the potential to drastically reduce environmental pollution caused by construction activities around the globe. 

Srubar joins a list of candidates – all under the age of 40 – working to advance environmental causes around the world. The roster includes leaders in fields such as sustainable design, wildlife law, shark conservation and carbon markets. In the coming months a committee will choose three finalists for the award. Then judges will select a winner to be announced at an Oct. 26 ceremony. Winners receive $100,000 and finalists take home $5,000 – made possible by a gift from the Anthony and Jeanne Pritzker Family Foundation.

Srubar said being included in such an impressive cohort of nominees is a true honor.

“For my living materials research and related entrepreneurial endeavors to be recognized in this way is both humbling and exhilarating,” he said. “Winning the award would bring world-renowned recognition and legitimacy to the idea that nature-based material solutions are critical to decarbonizing the construction industry and combatting the consequences of climate change.”

Srubar has been recognized for his research in a variety of venues recently. He was named to the  and was the American Ceramic Society’s Cements Division Early Career Award winner in 2023. Previously, he was selected as the BioEnvironmental Polymer Society Outstanding Young Scientist in 2021 and won a prestigious National Science Foundation CAREER award in 2020. To date, his laboratory has received over $12 million in sponsored research funding through the U.S. National Science Foundation, Air Force Research Laboratories, ARPA-E and DARPA’s Biological Technologies Office.

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The Breakthrough Energy Foundation has announced research by Wil Srubar is being recognized with a fellows award to support the development of cutting-edge climate technologies.

The foundation, a climate and sustainability organization created by Bill Gates, seeks to promote net zero energy solutions.

Srubar, an associate professor who has conducted major research into biomimetic and living materials, has developed an algae-based form of concrete, which has significant potential to drastically reduce environmental pollution caused by construction activities around the globe.

Concrete accounts for over seven percent of the world's annual greenhouse gas emissions.

The fellowship award is for his lab and spinout company, Minus Materials.

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Global cement production accounts for 7% of annual greenhouse gas emissions in large part through the burning of quarried limestone. Now, a CU Boulder-led research team has figured out a way to make cement production carbon neutral—and even carbon negative—by pulling carbon dioxide out of the air with the help of microalgae. 

The CU Boulder engineers and their colleagues at the and the National Renewable Energy Laboratory (NREL) have been rewarded for their innovative work with a $3.2 million grant from the U.S. Department of Energy’s (DOE) Advanced Research Projects Agency–Energy (ARPA-E). The research team was recently (Harnessing Emissions into Structures Taking Inputs from the Atmosphere) to develop and scale up the manufacture of biogenic limestone-based portland cement and help build a zero-carbon future.

“This is a really exciting moment for our team,” said Wil Srubar, lead principal investigator on the project and associate professor in Civil, Environmental and Architectural Engineering and CU Boulder’s Materials Science and Engineering Program. “For the industry, now is the time to solve this very wicked problem. We believe that we have one of the best solutions, if not the best solution, for the cement and concrete industry to address its carbon problem.” 

Concrete is one of the most ubiquitous materials on the planet, a staple of construction around the world. It starts as a mixture of water and portland cement, which forms a paste to which materials such as sand, gravel or crushed stone are added. The paste binds the aggregates together, and the mixture hardens into concrete. 

To make portland cement, the most common type of cement, limestone is extracted from large quarries and burned at high temperatures, releasing large amounts of carbon dioxide. The research team found that replacing quarried limestone with biologically grown limestone, a natural process that some species of calcareous microalgae complete through photosynthesis (just like growing coral reefs), creates a net carbon neutral way to make portland cement. In short, the carbon dioxide released into the atmosphere equals what the microalgae already captured. 

Ground limestone is also often used as a filler material in portland cement, typically replacing 15% of the mixture. By using biogenic limestone instead of quarried limestone as the filler, portland cement could become not only net neutral but also carbon negative by pulling carbon dioxide out of the atmosphere and storing it permanently in concrete.  

If all cement-based construction around the world was replaced with biogenic limestone cement, each year, a whopping 2 gigatons of carbon dioxide would no longer be pumped into the atmosphere and more than 250 million additional tons of carbon dioxide would be pulled out of the atmosphere and stored in these materials. 

This could theoretically happen overnight, as biogenic limestone can “plug and play” with modern cement production processes, said Srubar. 

“We see a world in which using concrete as we know it is a mechanism to heal the planet,” said Srubar. “We have the tools and the technology to do this today.” 

A scanning electron micrograph of a single coccolithophore cell, Emiliania huxleyi. (Credit: Wikimedia Commons / Alison R. Taylor, University of North Carolina Wilmington Microscopy Facility)

The coccolithophore has been part of the Black Sea ecology for millennia, and in the summer these calcite-shedding phytoplankton can color much of the Black Sea cyan. (Credit: NASA Goddard Space Flight Center, Flickr) 

Limestone in real time

Srubar, who leads the Living Materials Laboratory at CU Boulder, received a National Science Foundation CAREER award in 2020 to explore how to grow limestone particles using microalgae to produce concrete with positive environmental benefits. The idea came to him while snorkeling on his honeymoon in Thailand in 2017. 

He saw firsthand in coral reefs how nature grows its own durable, long-lasting structures from calcium carbonate, a main component of limestone. “If nature can grow limestone, why can’t we?” he thought. 

“There was a lot of clarity in what I had to pursue at that moment. And everything I've done since then has really been building up to this,” said Srubar. He and his team began to cultivate coccolithophores, cloudy white microalgae that sequester and store carbon dioxide in mineral form through photosynthesis. The only difference between limestone and what these organisms create in real time is a few million years. 

With only sunlight, seawater and dissolved carbon dioxide, these tiny organisms produce the largest amounts of new calcium carbonate on the planet and at a faster pace than coral reefs. Coccolithophore blooms in the world’s oceans are so big, they can be seen from space. 

“On the surface, they create these very intricate, beautiful calcium carbonate shells. It's basically an armor of limestone that surrounds the cells,” said Srubar. 

Students working in the Living Materials Laboratory, which utilizes calcifying microalgae to produce limestone and create a carbon neutral cement, as well as cement products which can slowly pull carbon dioxide out of the atmosphere and store it. (Credit: Glenn Asakawa/CU Boulder)

Commercializing coccolithophores

These microalgae are hardy little creatures, living in both warm and cold, salt and fresh waters around the world, making them great candidates for cultivation almost anywhere—in cities, on land, or at sea. According to the team’s estimates, only 1 to 2 million acres of open ponds would be required to produce all of the cement that the U.S. needs—0.5% of all land area in the U.S. and only 1% of the land used to grow corn. 

And limestone isn’t the only product microalgae can create: microalgae’s lipids, proteins, sugars and carbohydrates can be used to produce biofuels, food and cosmetics, meaning these microalgae could also be a source of other, more expensive co-products—helping to offset the costs of limestone production. 

To create these co-products from algal biomass and to scale up limestone production as quickly as possible, the Algal �ƹ���Ƶ Collection at UNCW is assisting with strain selection and growth optimization of the microalgae. NREL is providing state-of-the art molecular and analytical tools for conducting biochemical conversion of algal biomass to biofuels and bio-based products. 

There are companies interested in buying these materials, and the limestone is already available in limited quantities.

, a CU startup founded in 2021 and the team’s commercialization partner, is propelling the team’s research into the commercial space with financial support from investors and corporate partnerships, according to Srubar, a co-founder and acting CEO. Minus Materials previously won the university-wide Lab Venture Challenge pitch competition and secured $125,000 in seed funding for the enterprise. 

The current pace of global construction is staggering, on track to build a new New York City every month for the next 40 years. To Srubar, this global growth is not just an opportunity to convert buildings into carbon sinks but to clean up the construction industry. He hopes that replacing quarried limestone with a homegrown version can also improve air quality, reduce environmental damage and increase equitable access to building materials around the world. 

“We make more concrete than any other material on the planet, and that means it touches everybody's life,” said Srubar. “It's really important for us to remember that this material must be affordable and easy to produce, and the benefits must be shared on a global scale.”

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