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 us ed to produce small cavities that work as pressure-sensitive capacitors. Th e process is CMOS compatible, therefore, on-chip switched capacitor circuit s can be used for signal amplification. To enable transduction of normal fo rces 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 contac t 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 s ensor output data. (C) 2000 Elsevier Science S.A. Ail rights reserved.