New tactile sensor chip with silicone rubber cover

We report on a new tactile sensor chip developed for measuring distribution of forces on its surface. The chip has eight force-sensitive areas, called "taxel" with a pitch of 240 mu m. Surface micromachining techniques are used to produce small cavities that work as pressure-sensitive capacitors. The process is CMOS compatible, therefore, on-chip switched capacitor circuits can be used for signal amplification. To enable transduction of normal forces to the sensitive areas, we cover the sensor chip surface with silicone rubber. First, measurements show that the sensor's output can be explained by results from contact mechanics, We demonstrate this by the simple case of a hard sphere pressed in the silicone rubber cover. The center of contact can be measured within 2 mu m precision. The radius of the sphere and the load working on it can be estimated with high precision from the tactile sensor output data. (C) 2000 Elsevier Science S.A. Ail rights reserved.