Multifunctional flexible graphene oxide/bacterial cellulose composite paper platforms for realtime monitoring sweat and strain in wearable devices

Paper-based wearable sensors have gained significant attention in sweat analysis due to their widespread availability, comfortable wearability, and hygroscopic behavior. However, integrating functional components such as the conducting polymers in one sensor to realize the simultaneous and on-demand detection for the physical and chemical indexes compromises their stable performance under operation due to mismatch among various functional parts. We report a stable, multifunctional, and scalable paper-based flexible sensing platform for improved performance for in-situ sweat stimulating and analyzing of sweat as well as the monitoring of body motion. The welded honeycomb structure of composite paper formed in direct laser writing can provide a reversible and precise response in resistance during bending. The internal confined space containing the bacterial cellulose can induce an electrostatic enrichment of hydrogen ions in sweat, thus enhancing the pH-sensing sensitivity (68 mV pH-1). This spatial separating design for the two detections can further isolate the interfering, thus enabling the simultaneous and highly sensitive analysis of pH and movement. In addition, the controlled joule heating effect and the nano-fluid channels of the papers can help generate and rapidly transfer the sweat, further facilitating an on-demand and rapid responsive detection.