ABSTRACT
In this chapter we discuss haptic displays that can, under computer control, change their feel from slippery to sticky. These devices, most of which employ ultrasonic vibrations to modulate apparent coefficient of friction, build on a long tradition of displaying haptic information through the control of lateral or shear forces. For instance, one of the earliest studies in the field of haptics was Minsky’s [Minsky 95] sandpaper system. Minsky used variations in lateral forces through a joystick to create the sensation of a bumpy surface. The newer displays discussed here are similar, but can be touched by the fingertips directly (thus, they might be considered tactile displays). In addition, they control only frictional resistance to fingertip motion but do not have the ability to apply active forces to the fingertips. Nonetheless, spatial and temporal modulation of friction enables these displays to emulate a wide variety of textures.
