Breathable, recyclable, and solvent-free conductive films: versatile processing for flexible biointerfaces

Biointerface engineering is pivotal for the seamless integration of wearable sensors with skin, offering transformative potential in bioelectronics, personalized diagnostics, and human–computer interfaces. Nonetheless, creating high-performance biointerface materials that adhere effectively to the skin while simultaneously providing breathability and preserving mechanical compliance remains a formidable challenge. Here, we present a solvent-free, ion-conductive biointerface film fabricated via the physical crosslinking of soft polyethylene oxide with phytic acid. The resulting film exhibits excellent air permeability (1.89 ± 0.02 mg cm−2 h−1), self-adhesion (89.60 ± 1.45 kPa), and mechanical compliance (skin-compatible Young's modulus of approximately 0.42 MPa). Remarkably, the material can be recycled and reused over 10 times, and dissolved quickly in hot water at 60 °C, enabling facile reprocessing. We demonstrate its efficacy as a wearable sensor conformally attached to the knuckles, providing stable electrochemical signals that accurately track bending states. In addition, we demonstrate its application as a leaf patch for continuous monitoring of plant activity over 48 hours. These findings offer a sustainable and versatile platform for advancing the development of flexible wearable technologies.