Soft dielectrics for capacitive sensing in robot skins: Performance of different elastomer types

• Sensitivity depends on the mechanical and dielectric properties of the elastomer.
• It is not possible to identify an optimal general purpose elastomer.
• All the tested elastomers, were affected by a worsening of their properties due to ageing.
• The softness of the elastomer allows for a good response range of the sensor.

In a capacitive tactile sensor the dielectric layer plays an important role: both its electrical and mechanical properties affect the capacitance variation and the sensor response in terms of sensitivity, since the deformation ability of the dielectric layer allows for the detection of small pressures, and spatial resolution, since the dielectric layer acts as a low-pass spatial filter decreasing the spatial resolution. In this work we comparatively evaluate the effect of different elastomers on the performance of a capacitive sensor designed to cover large areas of a robot body. In particular, we compare the sensitivity, the spatial resolution and the durability of the sensor using foams, bulk elastomers and high permittivity composites.