Soft Electrodes for Simultaneous Bio-potential and Bio-impedance Study of the Face.

The human body's vascular system is a finely regulated network: Blood vessels can change in shape (i.e. constrict, or dilate), their elastic response may shift and they may undergo temporary and partial blockages due to pressure applied by skeletal muscles in their immediate vicinity. Simultaneous measurement
of muscle activation and the corresponding changes in vessel diameter, in particular in regions such as the face, is challenging, and the manner by which muscle activation constricts blood vessels has been experimentally largely overlooked. Here we report on a new electronic skin technology for facial investigations to address this challenge. By employing soft and dry electrode arrays we were able to perform
concurrent bio-potential and bio-impedance measurements, and to successfully capture subtle fluctuations in the temporal superficial artery diameter in response to facial muscle activity, which ultimately changes blood flow. The observed changes in the face, following muscle activation, were contested with measurements in the forearm and were found to be notably more intricate. Simultaneous mapping of the face's bio-potential and bio-impedance enabled us to gain insights into the
complex mechanisms through which facial muscles might modulate blood flow and
possibly affect human physiology.