Simulation of the current density distribution for transcranial electric current stimulation around the eye

s / Brain Stimulation 8 (2015) 395e411 406 *E-mail: patrique.fiedler@tu-ilmenau.de. Application of transcranial electrical stimulation (tES) systems is currently hampered by complicated and error-prone electrode placement and preparation, especially when intended for daily rehabilitation scenarios, in outpatient departments or at home. We present a novel flexible, compliant cap system with integrated textile stimulation electrodes. Unlike conventional headbands and cap concepts for tES, the novel cap allows for easy, reproducible application; considerably reducing error sources, preparation effort, and therefore enhanced usability. We compare the novel cap system to a conventional headband and sponge based system. The base material of the cap is a light-weight and flexible fabric allowing for quasi homogeneous contact pressure at all covered head areas. The cut of the cap can easily be adapted to individual head geometries. Textile, 5x7 cm sized electrodes based on silver coated fibers are integrated at distinct positions. The cap features pockets behind each textile electrode, that easily accessible from outsidewhile the cap is worn on the head. Hydrated sponges can be added into these pockets to allow for hydration of the electrodes. Ring-shaped silicone-impregnated areas around each electrode inhibit fluid running and spreading. Figure 1. Novel cap system with textile electrodes at positions Fp2 and C3: a) Outside view, b) Cap turned inside out. Our results demonstrate the electrode-skin impedances of both systems to be comparable after an initial settling time of approx. 10 min. The interfacial impedance is below 50 kOhm when applied in bipolar setups, thus rendering them compatible with commercially available stimulation systems. Furthermore, we show that the silicone-impregnated textile ring inhibits extensive fluid spreading in the fabric during typical application durations of several minutes. In conclusion, the novel cap system allows for rapid, easy application, reduces possible sources for preparation errors in electrode placements and can hence potentially replace the conventional caps and headband systems in future.