Dry-printed electrodes for transcutaneous electrical stimulation of inervated muscles: Towards wearable and closed-loop stimulation

Despite growing interest in transcutaneous electrical stimulation, the need for precise electrode placement, limited long-term stability, and user inconvenience hinders widespread adoption. To address these issues, soft screen-printed electrode arrays were designed and tested for recording and stimulation on the neck and face of healthy subjects. Contact impedance was measured and modeled for both printed (dry) and conventional gel electrodes. Stimulation efficacy was evaluated using surface electromyography and mechanical movement recorded with an inertial measurement unit. Activation thresholds and perceived discomfort were comparable between electrode types. In addition to validating their effectiveness for transcutaneous stimulation of innervated muscles, we demonstrated closed-loop facial recording and stimulation using dry electrodes. By combining reliable stimulation with user comfort, our results pave the way for wearable neuromodulation systems for clinical and home use, particularly in restoring facial symmetry for individuals with neuromuscular impairments.