Polymer Conductive Polymer for Flexible Biosensors

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Max-Planck-Institut für Polymerforschung

FAULHABER Drive Systems

A research team at the Max Planck Institute for Polymer Research has developed the conductive polymer Pedot:PSS using the transfer printing process and modified it through targeted diffusion of plasticizer from the substrate into the polymer film. These deformable sensors can be worn directly on the skin.

A patch that measures the heartbeat or detects biomarkers in sweat while feeling as soft and flexible as human skin—such visions are becoming tangible through new material developments. To realize ideas like these as well as wearable and skin-like electronics in general, materials are needed that possess both high electrical conductivity and mechanical stretchability. A team of scientists at the Max Planck Institute for Polymer Research, led by Dr. Ulrike Kraft, is currently working on this challenge. However, stretchability and electrical conductivity often conflict with each other, making the development of suitable materials difficult.

The plasticizers contained in the substrates diffuse into the conductive polymer, enhancing both the electrical performance and mechanical properties.

Carla Volkert

In their current study, the researchers demonstrate how this trade-off can be overcome through the targeted transfer of plasticizers from the substrate into the Pedot:PSS polymer film. To achieve this, a previously established transfer printing process is used, enabling conductive polymer films to be transferred quickly, reliably, and straightforwardly onto stretchable, biodegradable substrates. The conductive polymer Pedot:PSS, which combines transparency, flexibility, and biocompatibility, is used as the material of choice. "The plasticizers contained in the substrates diffuse into the conductive polymer, improving both the electrical performance and mechanical properties," explains Carla Volkert, doctoral student and first author of the study. Additionally, the approach provides fundamental insights into the behavior of stretchable electronic materials.

Our method simultaneously improves the stretchability and electrical conductivity of Pedot:PSS— an important step towards skin-wearable biosensors.

Ulrike Kraft

Through a combination of various analytical methods—including electrical characterization, microscopic imaging, atomic force microscopy, and Raman spectroscopy—the researchers gained new insights into the morphological and electronic changes of Pedot:PSS under strain. Particularly noteworthy is the observed self-organization of polymer chains, which increases electrical conductivity under mechanical stress. "Our method simultaneously improves the stretchability and electrical conductivity of Pedot:PSS—an important step toward skin-close wearable biosensors," explains Ulrike Kraft, head of the Organic Bioelectronics research group.

These results not only make a significant contribution to fundamental research in the field of soft, conductive materials but also open up new perspectives for the development of innovative technologies—from flexible electrodes for electrocardiograms (ECG) to stretchable biosensors on the skin that can detect and monitor analytes like stress hormones in sweat. The next step is to extend the process to the production and characterization of stretchable biosensors.

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