Shu Yang, the Joseph Bordogna Professor and chair of materials science and engineering in Penn Engineering, looks at her research through the lens of biomimicry: life forms and natural shapes have inspired her unique engineering solutions that span agriculture, building cooling and heating and reversible adhesives. For Dr. Yang, who also holds an appointment in chemical and biomolecular engineering, each of her innovations start with changes on a fundamental level that can then grow into scalable and impactful products. Her creative approach, breadth of topics, and overwhelming number of applied inventions resulted in her being named the 2023 Penn Center for Innovation Inventor of the Year.

“I continually ask myself what kind of research and what kinds of new technologies will make the biggest societal impact?” says Dr. Yang. “I love examining products such as construction materials, windows and even adhesives, and asking my group members how they can be more effective and consume less energy. I look to nature over and over again to find the answers.”

Dr. Yang uses kirigami, the Asian art of cutting and folding materials that is similar to origami, to mimic nature’s link between structure and function in her own inventions. Just as the hexagonal shape of the cells in beehives keeps the entire structure cool without the need for an external energy source, one of Dr. Yang’s inventions, designed with kirigami techniques, pulls water from the air passively. 

“We created kirigami water collectors, sheets of plastic made up of unique, 3D pyramid structures,” says Dr. Yang. “The pyramid structures themselves trap air into vortices, like mini tornados. Moisture in the air in these tiny tornados is pulled onto the surface of the kirigami sheet with the help of a chemical coating that attracts water. The original device was made to provide fresh water from fog while dehumidifying large indoor and outdoor spaces, but it can be applied to a wide range of needs.”

As part of a $2.2 million, multi-university U.S. Department of Energy (DOE) project, Dr. Yang is redesigning these kirigami water collectors to be used in wood desiccation, a process required before wood can be burned to generate heat and power. The project will help the wood-drying industry to reach carbon-pollution-free electricity use by 2035. “The new design is a copper kirigami sheet coated with desiccant,” says Dr. Yang. “Recently, we needed to prepare 340 of these sheets. Once a sheet was made, it needed to be placed straight into the oven to keep it from sucking moisture from the air in the lab. That’s how immediately they work.”

Another iteration of the desiccant will be used to make food drying more efficient in a multi-million dollar DOE project that Dr. Yang and her colleagues were just awarded this past fall. “Food desiccation is important for food preservation, storage and transport,” says Dr. Yang. “The need to dry food efficiently will continue to grow as the population doubles and we face more severe food scarcity. We will need to keep food fresh for longer, transport it longer distances, and pack it into smaller spaces to conserve energy and resources.”

While kirigami has taken center stage in the Yang lab, she continues to find new techniques to mimic natural structures in engineering. Funded by a $4.6 million grant from the National Science Foundation's (NSF) Eco Future Manufacturing Program (FMRG), Dr. Yang leads a team from Penn, Princeton University, Rowan  University, and Rutgers University to develop self-morphing building blocks that can be assembled into human-scale structures, maximizing strength and minimizing weight in the same way evolution has optimized biological organisms such as wood, chitin and bone at the cellular level. 

Additionally, funded by $2.4 million from the DOE, Dr. Yang is working with Masoud Akbarzadeh, an assistant professor of architecture in the Weitzman School of Design and director of the Polyhedral Structures Laboratory, to produce 3D-printed concrete with a porous design that allows for this building material itself to pull carbon dioxide out of the air.

“Cement is the third-largest industrial source of pollution,” says Dr. Yang. “Producing one ton of cement contributes over 1,300 pounds of carbon dioxide as well as the release of noxious gasses including sulfur dioxide, nitrogen oxide and carbon monoxide into the air. Our porous cement slab design conserves up to 60% of the material needed to make the structure and every 10 pounds of printed concrete structure has the potential to pull 0.9 pounds of carbon dioxide from the environment.”

“We are very excited about these new building materials because they are not only applicable for commercial buildings, but could also be used in low-income housing and post-disaster relief shelters,” says Dr. Yang. 

Soon, Dr. Yang’s inventions will be tackling real-world problems from wood desiccation to sustainable building materials.

Adapted from a Penn Engineering news release by Melissa Pappas, December 20, 2023.