Characterization of the electrical resistance of carbon-black-filled silicone: Application to a flexible and stretchable robot skin

Providing robots with the capability of sensing their surrounding environment is an important feature that would lead to a more intuitive and safe physical human-robot interaction. This paper proposes a new design of homogeneous flexible and stretchable robot skin based on carbon-black-filled (CBF) silicone and conductive fabric that can sense multiple contact locations as well as applied pressure. CBF silicone has been already used in sensing technology but its piezoresistivity is still largely misunderstood. This particular behavior is investigated in this paper through a set of experiments conducted on isolated sensing cells. Using the results of these experiments, a model describing the variation of the resistivity in the CBF silicone as a function of the applied pressure is proposed. Based on this model, a simple way to accurately estimate the applied pressure in real time is demonstrated. Finally, using this improved knowledge of the behaviour of the CBF silicone, the fabrication of a fully functional sensor array is presented. The proposed design has the particularity of circumventing the well-known problem of cross-talk between sensing cells.