For a sustainable future, scientists rethink plastics and devices

UChicago scientists and engineers seek to transform plastics, electronics, transportation

Modern society is now starting to feel the real-world effects of climate change, after more than a century of unrestrained carbon emissions, overuse of natural resources, and irresponsible production of material waste. The rise of atmospheric carbon dioxide has contributed to a warming climate, which means rising sea levels, more droughts, heat waves, and wildfires, and stronger, more frequent tropical storms.

Confronting these challenges will take an all-hands-on-deck approach to adapt to changes that have already taken place and prevent things from getting worse in the future. While governments and businesses can try to affect change through regulation, policy, and investment, science and engineering can play a crucial role by creating new technologies that will change the way we live, the products we use, how we travel, and how we power our world.

Scientists and engineers at the University of Chicago and Argonne National Laboratory are already answering the challenge, using biomaterials, advanced polymers, and artificial intelligence to engineer new materials that are fully recyclable and biodegradable from the ground up, without sacrificing the useful qualities of traditional plastics and consumer products. At the same time, these new materials can be engineered with specific properties to incorporate them into a new generation of electronics, better batteries, clean energy systems, and more.

This work has the potential to advance technology across the board, while reducing environmental harms and enabling human society to move forward in a more sustainable manner. With a decade of advances in molecular engineering, a storied history of materials science in the physical sciences, and crucial expertise and resources from Argonne, UChicago can transform the way in which impactful materials science and engineering is done, driven by sustainability goals and in coordination with insights from economics and policy.

Rethinking plastics from the ground up

Perhaps no material has contributed more to our modern way of life than plastic. Plastic-made from polymers, or large molecules consisting of many repeating subunits-is lightweight, strong, flexible, and most importantly, inexpensive to produce. It keeps our food fresh and makes our clothes warm. It’s in the circuit boards and cases of our smartphones and computers, it makes our cars and aircraft lighter and more fuel-efficient, and it saves lives in things like helmets, airbags, face masks, and medical equipment.

But one advantage of plastic, by design, is also a curse: it can take centuries to break down, if at all. The world produces more than 350 million metric tons of plastics annually-an already staggering number expected to reach 1,800 million tons by 2050--and yet 60% of all plastic ever produced has been thrown away in landfills or the oceans. The problem is so bad that it has been estimated that plastic in our oceans will outweigh all the fish in our seas by 2050.

Many of us think we’re doing our part to save the planet by dutifully separating paper and plastics for the recycling bin. But one of the reasons plastics are so useful and ubiquitous is because they were never designed to break down in the first place, no matter how they are disposed of by consumers. Modern-day plastics are also derived from fossil fuels like petroleum and natural gas.

"When plastics were first designed 50 years ago, they were never meant to be degradable," said Stuart Rowan, Barry L. MacLean Professor for Molecular Engineering Innovation and Enterprise at the Pritzker School of Molecular Engineering (PME) and the Department of Chemistry, with a joint appointment at Argonne National Laboratory. "The end of life wasn’t planned, because they could always make more."

Rowan and his colleagues are working on a unique way to overcome both of these challenges by creating plastic-like materials with the ultimate renewable material: plants. Cellulose, the material that makes up the cell walls of plants, is a natural polymer that can be used to make bioplastics. There are already some commercially available plastics made from plants, but they aren’t quite as strong or durable as traditional plastics. Rowan and his lab are working on ways to improve bioplastics to compete with traditional plastics at a competitive cost.

One method is by extracting cellulose nanomaterials from Miscanthus giganteus, a perennial grass with bamboo-like stems that can grow over 12 feet a season. These grasses have drawn a lot of attention from researchers as a potential biofuel because they’re hardy, use water efficiently, and can grow on marginal land and thus don’t compete with food crops.

Working with researchers at Argonne, Rowan and his team have developed processes to extract cellulose nanomaterials from these grasses at an industrial scale. Now, they’re studying them to see how they can be used to improve bioplastics by increasing their resistance to temperature, for example, or improving their barrier properties to create better packaging.

They are also working with other materials researchers at PME and computer scientists from UChicago and Argonne to use artificial intelligence and machine learning to help design the next generation of plastics that are engineered to be more recyclable or biodegradable. AI can be used to identify key characteristics of materials, model the millions of combinations of properties and structures that give them the desired properties, and determine ways to engineer them with new functionality and performance for sustainability.

Democratizing electronics manufacturing

Another significant source of plastic material waste comes from consumer electronics, from smartphones and laptops to TVs, video game consoles, and all of their accessories. Only 17% of the nearly 54 million metric tons of electronic waste generated in 2019 was recycled, much of which was made from plastic and polymer-based materials. To tackle this issue, Rowan and Junhong Chen, Crown Family Professor of Molecular Engineering at PME and lead water strategist at Argonne, are working on another innovative project to transform how electronics are manufactured.

In 2020, Rowan, Chen and colleagues from UChicago, Northwestern, University of Illinois Urbana-Champaign (UIUC) and the University of Illinois at Chicago received a $9.15 million research grant from the National Science Foundation to develop a sustainable manufacturing system for producing biodegradable electronic devices. Over the course of the five-year project, they hope to develop a prototype for an accessible manufacturing system that would eventually allow anyone to 3D print electronic devices at school, libraries, or even at home.

The system will use inks derived from plants, using the same cellulose materials that Rowan is learning how to cultivate and extract from grasses. Right now, most 3D printing is used to create passive, structural components, but Chen says that these bio-based inks can be engineered with different metallic, semiconducting, or insulating properties to be used in electronics. Rowan is working with plant biologists from UIUC to understand how different growing conditions affect the yield and type of cellulose nanomaterials they can harvest from the plants, and how different conditions affect their functional properties.

Initially, the team will use the process to build simple electronic sensors that can be used to monitor the temperature, light, humidity, and water conditions where the plants are growing, creating a feedback loop to further refine the process. Eventually, the platform can evolve to produce more sophisticated devices and batteries. The system will also be open-sourced, to encourage contributions from other researchers and the broader community.

"We hope with this platform we can really encourage bio-based manufacturing that can produce electronic devices with minimum negative environmental impact," Chen said. "It’s really energizing to think about how one day people could experiment with it themselves, grow plants at home or make designs for their own devices. The citizen science type of involvement and student engagement is going to be really exciting once we get this to work."

It all seems like something from a William Gibson novel, with average consumers able to print out their own smartphones and bespoke electronic devices from plant-based inks. But Rowan says he has no doubt the potential is there to move forward with more functional, sustainable materials that are designed from scratch to avoid waste and build a circular economy.

"We’re not there yet, but we believe we will be able to make new, biodegradable materials that are just the same or better than traditional plastics," Rowan said. "Our job as scientists is to make sure all of the options are available, and then the question is, can we make them commercially viable? Environmental policies of governments across the planet as well as the price of oil, the current feedstock for plastics, will also play a role here."

Solving the battery challenge

The competing cost of oil also looms over another scientific advancement that could break humanity’s dependence on our most environmentally destructive inventions: gas-powered vehicles and other fossil fuel-based energy systems.

According to the Environmental Protection Agency , transportation currently accounts for about 28% of greenhouse gas emissions in the United States. Electricity generation from sources like coal and natural gas account for another 27%. The key technology to decarbonizing both of those industries is the battery-longer lasting, faster charging ones to power electrical vehicles, and powerful, efficient batteries to store electricity for the power grid generated by renewable sources like solar and wind.

Chibueze Amanchukwu, Neubauer Family Assistant Professor of Molecular Engineering at PME, calls batteries the "kingmaker" of the energy challenge. "Solving the battery challenge can solve many of the other challenges related to climate change," he said. "Not only can they power electric vehicles, but they can also fill the void to store and provide excess energy when the wind isn’t blowing or the sun isn’t shining, to power our homes or power manufacturing plants 24/7."

Like plastics, engineering better batteries is a materials problem. At the simplest level, batteries consist of three components: two terminals, the negatively charged anode and the positively charged cathode, which are typically electron conductors, and the electrolyte, a chemical medium that separates the terminals. When devices like a light bulb or electrical circuit are attached to the battery, electrochemical reactions in the terminals enable electrons to be transported through the electrolyte to generate a current and power the device.

Lithium-ion batteries have an anode made of graphite and a cathode made of lithium transition metal oxide. They power everything from smartphones and laptops to electric vehicles, but lithium metal batteries, which replace the graphite anode with lithium metal, could potentially store twice as much energy. Unfortunately, they aren’t stable enough for widespread use yet.

Amanchukwu’s research is focused on developing better electrolyte solutions to harness the power of lithium metal batteries, using AI and machine learning to guide the process. Electrolytes consist of dozens of different ions, salts, solvents, and other additives. Each can be mixed in different amounts to potentially change the performance of a battery, creating what Amanchukwu calls a "combinatorial nightmare." It’s impossible to tell how a given combination will perform without creating and testing it. So, AI algorithms give his team a way to model different combinations, predict how they will perform, and design the best candidates before testing.

"You can’t wait for 30 years to mix all the different combinations and find out what works, because we don’t have time," he said. "These challenges are so great that we can’t just sit around and wait for somebody else to solve it. We have to come up with these tools and techniques to solve this urgent crisis that we face."

Accelerating the process of building better batteries helps clear the final hurdle to more widespread adoption by lowering their cost. The average driver around the world can’t afford a Tesla-and a huge component of that price is the cost of its battery. Amanchukwu, who grew up in Nigeria, said making sustainable technologies more accessible everywhere is what drives his work.

"I’ve always been reassured by the impact that working on batteries can have on the world," he said. "You can enable developing countries like Nigeria to grow sustainably and modernize the energy economy without having to punish the planet in the process."

New sources for ’white gold’

Even as batteries have the potential to solve the renewable energy puzzle, they pose their own conundrum. How do we supply the raw materials to make enough batteries responsibly and sustainably? Lithium is a popular material for batteries because it’s light and stores a lot of energy efficiently, and as more industries transition to clean energy, demand for the element will only increase. However, global supplies of lithium are limited and concentrated in just a few locations. It’s mined from rock in Australia, or extracted from brines that contain concentrated lithium ions in saltwater flats in China and three South American countries known as the "Lithium Triangle"--Argentina, Bolivia and Chile.

The World Bank estimates that five times more lithium than is currently mined annually will be needed to meet global demand by 2050, and with demand projected to increase even more in coming years, the supply of this "white gold" may be exhausted as soon as 2025. Traditional lithium mining also has a heavy carbon footprint and poses a serious environmental threat. It requires harsh chemical treatments to leach lithium from rock and uses tremendous amounts of heat and energy to pump and evaporate the saltwater brines. Plus, with just a handful of countries providing the world’s supply, it poses potential trade and security issues.

Scientists like Asst. Prof. Chong Liu at PME are searching for more efficient ways to procure lithium and diversify the world’s supply. Her lab’s research focuses on new materials that can be used in the electrochemical processes to extract lithium from brines like those found in South America. Different materials with different structural properties can be used to build electrodes that attract lithium and separate it from the water. As with the other cutting-edge materials research, AI and machine learning can help sift through millions of combinations of different features to identify the right combinations of chemicals and elements that could make the best material. It would then be used to extract lithium from current sources in a more efficient and less carbon intensive process.

Eventually, Liu hopes this process can be applied to the world’s most abundant natural resource. Seawater contains billions of tons of lithium, by far the largest source available, but it’s also present in very low concentrations, just 0.2 parts per million. A new material to pull lithium from seawater would have to be highly selective and remain stable in salt water for a long time. Once perfected, these new materials and processes can also be used to separate uranium and rare elements from other sources, which will be critical for building renewable energy infrastructure like solar panels and wind turbines.

"That’s the material challenge, but if we can solve that moving on from there is much easier," Liu said. "Seawater is the ultimate goal, and once we can do that the other sources with higher concentrations of lithium and other elements will be less challenging."

Training the next generation

Confronting climate change is a global challenge that will extend long past the careers of these researchers and their peers. Future generations of scientists and engineers will be forced to reckon with its effects in nearly every aspect of their work and develop new skills to account for sustainability. The University of Chicago, its affiliated national labs, and network of partners are launching new programs to train the next generation of researchers on this front. For example, in 2020, UChicago received a five-year, $3 million NSF Research Traineeship grant to support a joint program with Argonne that will train 150 students in integrating molecular engineering with artificial intelligence to promote sustainability.

New initiatives like this join other longstanding federally funded programs and partnerships that form a foundation for materials research. The Department of Energy-supported Midwest Integrated Center for Computational Materials (MICCoM), headquartered at Argonne, develops and disseminates interoperable computational tools that enable the community to simulate and predict properties of functional materials for energy conversion. The Center for Hierarchical Materials Design (CHIMAD), a partnership with Argonne and Northwestern University funded by the National Institute of Standards and Technology, also seeks to develop innovative materials through the use of state-of-the-art computational methods and artificial intelligence tools.

The most venerable of these programs is the NSF-funded Materials Research Science and Engineering Center (MRSEC), which incubates innovative research, supports seed projects, and operates shared facilities to produce design principles for the next generation of materials. UChicago has been the steward of MRSEC continuously for sixty years. Margaret Gardel, the current director of MRSEC, says the consistent focus on collaboration and education helps create a sense of community.

"It creates infrastructure that goes beyond the reach of individual laboratories," said Gardel, who is also the Horace B. Horton Professor of Physics and Molecular Engineering at the Institute for Biophysical Dynamics and the James Franck Institute. "It’s the commitment to shared facilities, support of graduate students working jointly between multiple labs, educational and outreach activities and funding for seed projects. Each component is one small part, but all of these things together help set a tone and an institutional culture for innovation in material science."

The challenges of developing new materials to deliver sustainability, reduce waste, transform clean energy technologies, and integrate into industrial applications present direct, actionable opportunities for science and engineering at UChicago and its affiliates. Corporate and government partners have an immediate need to implement sustainable materials and sensors into their production processes and infrastructure, and UChicago already has the foundations in place to build a research platform that can meet these challenges. With expanded academic expertise, education and training programs, and fabrication and testing facilities across its research ecosystem, UChicago and its affiliates will have the capability to rapidly translate fundamental discoveries in materials science into practical solutions to engineer a sustainable future.

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