Flexible Polypyrrole Composite Films with Organic and Inorganic Fillers for Electrocardiographic Sensing Applications

Conductive polymers have emerged as promising materials for flexible electrodes in wearable biomedical devices. Among them, polypyrrole (PPy) is particularly attractive due to its intrinsic electrical conductivity, chemical stability, and compatibility with soft substrates. However, pure PPy films may exhibit limited mechanical robustness and reduced stability under repeated deformation. To address these limitations, the incorporation of functional fillers represents an effective strategy to tailor the structural, electrical, and mechanical properties of the polymer matrix.

In this study, composite thin films based on p-toluenesulfonic acid-doped polypyrrole (PPy-TSA) incorporating both organic and inorganic fillers, such as polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), graphene (GR), carbon nanotubes (CNTs), and zeolite (ZE), were developed and investigated. The films were obtained by electrochemical polymerization using a galvanostatic method, where pyrrole was polymerized in the presence of fillers dispersed in the electrolyte. The fillers were commercially available, while the PPy matrix was synthesized in situ.

The morphology and structural organization of the films were analyzed by scanning electron microscopy (SEM), while Fourier-transform infrared (FTIR) and ultraviolet–visible (UV–Vis) spectroscopy were used to investigate the chemical structure and interactions within the composites. Electrical properties were evaluated through conductivity and sheet resistance measurements, including temperature-dependent analysis and bending tests to assess stability under deformation.

The results show that the combined incorporation of organic and inorganic fillers enables tuning of both electrical response and mechanical integrity. These properties are relevant for the development of flexible electrodes capable of detecting low-amplitude bioelectrical signals. The investigated PPy composite films demonstrate promising potential for electrocardiographic (ECG) sensing in wearable health monitoring systems.