Transcranial Electrical Stimulation and Recording of Brain Activity using Freestanding Plant-Based Conducting Polymer Hydrogel Composites

Transcranial electrical stimulation is a noninvasive neurostimulation technique with a wide range of therapeutic applications. However, current electrode materials are typically not optimized for this abiotic/biotic interface which requires high charge capacity, operational stability, and conformability. Here, a plant-based composite electrode material based on the combination of aloe vera (AV) hydrogel and a conducting polymer (CP; poly(3,4-ethylenedioxythiophene):polystyrene sulfonate, PEDOT:PSS) is reported. This material system is fabricated into films and provides biocompatibility, conformability, and stability, while offering desirable electrical properties of the PEDOT:PSS. AVCP films are also molded onto the rough surface of the skull leading to a mechanically stable and robust interface. The in vivo efficacy of the AVCP films is verified to function as stimulating and recording electrodes by placing them on the skull of a rat and concomitantly inducing focal seizures and acquiring the evoked neural activity. AVCP films pave the way for high-quality biological interfaces that are broadly applicable and can facilitate advances in closed-loop responsive stimulation devices.