Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Ying Diao, University of Illinois at Urbana-Champaign

Printing Polymer Electronics for Sustainable Earth and Habitable Mars

Written by Sophia Chen

During Ying Diao’s talk on Wednesday, she showed an image of a printer roll—not of paper, but semiconductors. “Organic electronics can be made […] akin to the way we make newspapers,” she said. These methods, which fall under the technique of 3D printing, promise cheap, high-throughput, and on-demand production. Consequently, researchers are investigating methods and materials for applications ranging from solar power to agriculture. Diao discussed the state of the technology in her talk, titled “Printing Polymer Electronics for Sustainable Earth and Habitable Mars.”

For their printed electronics, Diao’s laboratory uses conjugated polymers. While conjugated polymers are inherently semiconductors, when doped, these organic molecules can be as conductive as metals. Such organic molecules are already used in wearable electronics such as the organic light-emitting diodes in smartwatches. Researchers can modulate these materials’ conductivity over 14 orders of magnitude, she said. They have also recently used three-dimensional conjugated polymers to create structural color, where an object’s color derives from light interference with microscale or nanoscale structures. (Many animals, such as butterflies, exhibit structural color.) They also discover and design new materials using both physics-based approaches as well as artificial-intelligence-aided approaches.

Diao believes the future generation of organic electronics materials will be semiconductors that are chiral. The structure of chiral materials exhibits either right-handedness or left-handedness, meaning they lack mirror symmetry. (A helix is an example of a chiral structure.) Chiral structures are common in nature, such as in chlorophyll. The chlorophyll’s chirality makes charge transport much more efficient during photosynthesis. Chiral organic semiconductors could offer similar advantages. In recent work, her team found that they could create helical organic semiconductors through 3D printing. The chirality emerged by adjusting the flow rate and concentration of the material during printing.

Notably, when Diao and her group analyzed the material, they found that it exhibited chirality on multiple scales—from the micron-scale to the nanometer-scale. “We have a helix within a helix within a helix,” she said. This nested helicity also occurs in collagen.

Chiral organic semiconductors would be well-suited for various next-generation electronics, said Diao. For example, when hit with light, chiral molecules sustain excitons longer than planar molecules, a quality useful for solar cells.  They could also be useful for spintronics.

Diao ended her talk discussing a prototype device using printed electronics to aid agriculture. They designed the device with futuristic missions for inhabiting Mars in mind. The device consists of a stretchable sensor for monitoring the growth rate for plants. Printed electronics are promising for extraterrestrial applications because they are lightweight and high performance, she said.

Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.