Innovative stretchable plastics achieve electrical conductivity using microscopic whisker-like fibers, enabling next-gen flexible electronics.
A flexible, electrically conductive plastic may help advance the next generation of implantable biomedical technologies, including more durable pacemakers and long-term glucose monitoring systems, according to researchers at Penn State University.
Led by chemical engineering professor Enrique Gomez, the research team investigated PEDOT:PSS — a soft, conductive polymer widely used in soft robotics and touchscreen technologies. By incorporating specific salt additives and water into the material, the team discovered that its internal structure forms fine, hair-like fibers that significantly enhance electrical conductivity. Their findings were recently published in Nature Communications.
One of the major hurdles in developing implantable bioelectronics is bridging the difference between how the human body and electronic devices transmit electricity. While computers rely on electron flow through metals and semiconductors, the body uses ionic currents — electrical signals carried by charged particles dissolved in fluids.
PEDOT:PSS is particularly promising because it can conduct electrons while remaining responsive to ionic signals, making it well-suited for bioelectronic interfaces. However, its underlying structural behavior has not been fully understood.
To gain deeper insight, the researchers employed cryogenic electron microscopy (cryo-EM), an advanced imaging technique capable of visualizing materials at near-atomic resolution. Instead of using light, cryo-EM uses electron beams to examine microscopic structures in extraordinary detail.
The team prepared ultra-thin samples of the polymer and modified their chemical composition by introducing various salt additives. These samples were rapidly frozen in liquid ethane at approximately -180°C to preserve their structure during imaging and prevent damage from high-energy electron beams.
Through atomic-level analysis, the researchers observed that adding salts promotes the formation of whisker-like fibers within the gel-like polymer. These microscopic fibers serve as pathways for both ion and electron transport, boosting overall conductivity. Samples treated with salt displayed a denser fiber network and improved electrical performance.
The study also highlighted the importance of water. When water is absorbed, the polymer becomes softer and more stretchable. Lithium-based salts were found to enhance water uptake, further increasing flexibility. In contrast, dry samples became brittle regardless of salt content, underscoring water’s crucial role in maintaining elasticity. Notably, electrical conductivity remained relatively stable even as water content increased — a rare and valuable combination of stretchability and reliable conductivity for implantable devices.
Researchers believe the salt additives help “template” or guide the formation of the internal fiber structure — a phenomenon not previously documented. Even after the material swells into a gel-like form, the conductive fiber network remains intact, preserving its performance.
Moving forward, the team plans to continue investigating how salts interact with polymer chains and influence fiber formation. A deeper understanding could enable further optimization of the material for applications such as pacemakers, epidermal sensors and electromyography systems used to evaluate nerve and muscle function.
The project also involved collaborators from Iowa State University and received funding support from the National Science Foundation, the Office of Naval Research and the National Institutes of Health.
The researchers emphasized that continued federal support remains essential for advancing scientific innovation, strengthening industry competitiveness and improving healthcare technologies worldwide.