A haptic sensor-acutuator system based on ultrasound elastography and electrorheological fluids for virtual reality applications in medicine. - Walaa Khaled; Helmut Ermert; Otto T. Bruhns; Stefan Reichling; Holger Böse; Mario Baumann; Gareth J. Monkman; Stefan Egersdörfer; A. Meier; D. Klein; Herbert Freimuth (CARS, 2003)