Printed facial skin electrodes as sensors of emotional affect

Electromyography of the zygomaticus major and the corrugator supercilii muscles is a well-established technique to capture positive and negative emotional affect. Despite the great potential, its wide adoption has been so far limited owing to several lingering technical limitations in contemporary electromyography electrodes. In this paper, we report on new printed electrode arrays, specifically designed to capture emotional affect, focusing on their unique and advantageous properties compared with conventional gelled electrodes. Inkjet- or screen-printing, combined with film cutting and lamination techniques, were used to produce customized electrode arrays. Conformity with the skin was guaranteed by printing on very thin and soft films. Unlike conventional gelled-surface electromyography electrodes, the printed electrode arrays are dry, allowing long-term and stable recording. Moreover, the large electrode arrays can be rapidly and conveniently placed on the subject's face, maintaining excellent electrode-skin compliance. Muscle localization was achieved despite inter-subject variability in facial features and electrode array position, as a result of high spatial resolution and source separation methodology. The presented electrode arrays open new opportunities in brain-machine interfacing, well-being investigations and mood monitoring.