Credit: Reprinted from Sensors and Actuators A: Physical 2017:264:289-297; Yin, J., Santos, V.J., and Posner, J.D. “Bioinspired flexible microfluidic shear force sensor skin,” with permission from Elsevier.
As the robot finger slides along a surface, serpentine channels filled with electrically conductive liquid metal and embedded in the rubber skin stretch on one side of the finger and compress on the other. This changes the amount of electricity that can flow through the channels, which can be measured and correlated with shear force and vibration.