Innovative stretchable plastics achieve electrical conductivity using microscopic whisker-like fibers, enabling next-gen flexible electronics.
Researchers at Penn State have developed a flexible, electrically conductive plastic that could advance the next generation of implantable medical devices, including longer-lasting pacemakers and glucose monitors, according to Enrique Gomez, a professor of chemical engineering.
The team focused on a material called PEDOT:PSS, commonly used in soft robotics and touchscreen technology. By experimenting with different salt additives and controlled amounts of water, the researchers were able to create tiny hair-like fibers within the plastic that significantly improve its ability to conduct electricity. Their findings were recently published in Nature Communications.
One key challenge in developing bio-compatible electronics is reconciling the way the human body and electronic devices handle electrical currents. “Our nerves transmit signals using ionic currents—essentially circuits of ions and salts—whereas electronics rely on electrons flowing through metals or semiconductors,” Gomez explained. PEDOT:PSS is unique because it can carry electrons while remaining responsive to the ionic currents in biological tissues.
Despite its potential, PEDOT:PSS’s behavior has not been fully understood. To investigate, the team used cryogenic electron microscopy (cryo-EM), a cutting-edge technique that uses electrons instead of light to image materials at near-atomic resolution. This allowed them to study the structure of the gel-like polymer in unprecedented detail.
The researchers prepared tiny droplets of the material, encased them in nanoscopic films, and varied the chemical composition by adding different salts. These samples were then rapidly frozen in liquid ethane at -180°C to preserve their structure while under observation. The high-resolution imaging revealed that salt additives promote the growth of whisker-like fibers, which enhance the material’s conductivity. Adding water made the polymer more stretchable, while lithium salts further increased its water absorption, creating a soft, flexible material without significantly affecting its electrical performance. In contrast, dry samples became brittle, demonstrating water’s critical role in mechanical flexibility.
The study also showed that salt additives help template the material’s internal structure, allowing it to remain conductive even after being softened with water. “The fibers formed by salts persist even when the material is hydrated, which helps maintain its electrical properties while making it compatible with biological tissues,” Gomez said.
Looking ahead, the team plans to continue exploring how different salts influence the polymer’s fiber formation and overall properties. A deeper understanding could optimize the material for use in pacemakers, skin sensors, and devices that monitor nerve and muscle activity.
The research team included co-authors from Penn State—Esther Gomez, Masoud Ghasemi, Farshad Nazari, Joshua T. Del Mundo, Yi-Chen Lan, Po-Hao Lai, Louis Y. Kirkley, Mohammed K.R. Aldahdooh, and Joseph Cho—as well as collaborators from Iowa State University, Baskar Ganapathysubramanian and Dhruv Gamdha. Funding was provided by the U.S. National Science Foundation, the Office of Naval Research, and the National Institutes of Health.
At Penn State, researchers continue to work on projects that improve health, safety, and quality of life, illustrating how federal support for research drives innovation that strengthens both the economy and society.