  Soft sensors that can discriminate shear and normal force could help provide
machines the fine control desirable for safe and effective physical
interactions with people. A capacitive sensor is made for this purpose,
composed of patterned elastomer and containing both fixed and sliding pillars
that allow the sensor to deform and buckle, much like skin itself. The sensor
differentiates between simultaneously applied pressure and shear. In addition,
finger proximity is detectable up to 15 mm, with a pressure and shear
sensitivity of 1 kPa and a displacement resolution of 50 $\mu$m. The operation
is demonstrated on a simple gripper holding a cup. The combination of features
and the straightforward fabrication method make this sensor a candidate for
implementation as a sensing skin for humanoid robotics applications.
