The team used lasers to create structured materials out of animal-protein powder. The process is like 3D printing and allows the scientists to tightly control the material’s architecture. Similar materials often require either painstaking processes or harsh chemicals to manufacture. 

“Being able to directly write a material with complex levels of structure is really interesting,” said Craig Arnold, the Susan Dod Brown Professor of Mechanical and Aerospace Engineering and Princeton’s vice dean for innovation. With their laser process, they can make specific material structures that have desirable properties.

In this case, they converted proteins into a porous sponge-like structured called an aerogel. This kept the material very lightweight, while keeping the surface area high. The researchers then tested their engineered aerogel and it successfully stored energy like a battery. Their aerogel stored as much or more electric charge than similar carbon-based materials that are already available.

The researchers had been using a protein from egg whites as their raw material in their initial tests of their laser process. But eggs got expensive. Then they hit on the idea of using another unusual protein source: the iron-rich protein called hemoglobin found in red blood cells. In the meat industry, millions of tons of biowaste gets discarded every year, and much of that is blood. 

“The exciting thing here is taking low-value materials and turning them into high-value materials,” said Arnold, an associated faculty member of the Princeton Materials Institute. 

The researchers believe this waste product could be an important source for creating aerogels using their laser process. 

“The point of this paper was not to make the best battery,” said Shuichiro Hayashi, postdoctoral researcher in Arnold’s group and lead author on the study. He said the purpose was to engineer functional materials with practical usage, and they did that. In addition to batteries, the team is also looking at using the aerogel as a heating material for melting ice, and as insulation, especially desirable for portable needs like cars or rocket ships. 

The study, “Laser Upcycling of Hemoglobin Protein Biowaste into Engineered Graphene Aerogel Architectures for 3D Supercapacitors,” was published in Advanced Science on February 24, 2025. In addition to Arnold and Hayashi, the co-authors include Marco Rupp, Jason X. Liu, Joseph W. Stiles, Ankit Das, Amelia Sanchirico and Samuel Moore of Princeton University. Support for the research was provided by Princeton University. Characterizations were conducted using the facilities of the Princeton Imaging and Analysis Center (IAC) which was partially supported by the Princeton Center for Complex Materials, a National Science Foundation (NSF)-MRSEC program (DMR-2011750).