Ava Waitz ’21 loves materials science and engineering. Her major “is a very cool mix of all the sciences, and it also seems like the closest thing to magic,” says Waitz, a fan of the Harry Potter series. “It allows one to create energy from sunlight, polymers that mimic the properties of skin, and metals that are lighter and stiffer.”

The discipline is also broadly applicable to addressing climate change, an issue Waitz is passionate about.

Through MIT’s Undergraduate Research Opportunities Program (UROP), she has worked on two long-term research projects related to the topic: one focused on the development of transparent solar cells that could be applied to large surface areas like windows, the other on analyzing greenhouse gas emissions with the ultimate goal of creating better regulations for controlling them.

In addition, in the summer of 2020, Waitz joined forces with some 40 other students in the new Rapid Response Group (RRG) created by MIT’s Environmental Solutions Initiative. The RRG develops materials such as scientific briefing documents to support stakeholders working on critical environmental issues. Waitz and three colleagues wrote a guide on improving recycling practices at MIT (according to an RRG report, the Institute’s recycling rate in FY2020 was 36%). One recommendation was that MIT raise awareness of commonly used items that cannot be recycled, such as dyed plastics and stained cardboard (think large red cups and greasy pizza boxes).

Toward transparent solar cells

Majoring in materials science has enabled Waitz to explore the ways in which materials design and use can drive progress toward a low-carbon future. For example, in one of her UROP projects, she investigated whether silver nanowires could improve transparent solar cells. Success could enable solar cells to be used in many more ways, providing power from the windows of buildings or car surfaces.

While transparent solar cells exist today, they are made using oxide coatings that are expensive and brittle. Working in the laboratory of Professor Jeffrey C. Grossman, head of the Department of Materials Science and Engineering and the Morton and Claire Goulder and Family Professor in Environmental Systems, Waitz tried swapping the conventional oxide coatings with silver nanowires. “Silver nanowires can also be transparent, but they are cheaper and flexible,” Waitz says.

Next, she worked on depositing the silver nanowires onto a substrate using spray-coating. After assembling a machine and testing a variety of factors, such as optimal spray distance, machine speed, and the best concentration of nanowires, “we succeeded in making some flexible solar cells,” Waitz says. “Their performance was low, and they were only semitransparent, but it was pretty cool to hold a fully functioning device fabricated with the machine I put together.”

Addressing emissions

As fascinated as Waitz is with the emerging technologies key to addressing climate change, she is also interested in their limitations, including the policy and economic factors that influence technology adoption. That’s why as a first-year student, she reached out to Jessika Trancik, an associate professor in the Institute for Data, Systems, and Society, to see if she could work with her on some of the data-informed models Trancik uses to evaluate the economic and environmental impacts of energy technologies.

Waitz ended up working on a UROP with Trancik that involved industries with “super-emitters,” or those where a majority of greenhouse gas emissions come from a few poorly performing devices. Natural gas is a good example. A small percentage of the pipes that carry the gas produce a large fraction of daily emissions, according to one study Waitz contributed to. However, there are trade-offs involved in solving the problem. For example, since it takes time and money to identify and repair the faulty pipes, it could actually be more cost-effective to randomly replace pipes across the board, Waitz says. Modeling like that done in the Trancik lab can help clarify which approach is best.

On to China

What’s next for the soon-to-be MIT alum? Waitz is heading to Tsinghua University in Beijing as a Schwarzman Scholar. She is one of four MIT students among the 140 selected nationally from a field of 3,600 applicants. The one-year program, through which Waitz will earn a master’s degree in global affairs, is designed to “build a global community of future leaders who will serve to deepen understanding between China and the rest of the world,” according to the Schwarzman Scholar website.

At Tsinghua, Waitz aims to combine her interests in materials science and the systems those materials become a part of by studying the “circular materials economy,” or how materials can be recycled and reused. She is especially interested in China’s policy efforts and infrastructure for reusing waste materials. Ultimately, she’d like to become an academic “doing research related to this kind of materials-systems interface.”

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