The generation and presentation of tactile stimuli presents a unique challenge: Unlike vision and audition, in which standard equipment such as monitors and audio systems can be used for most experiments, tactile stimuli and/or stimulators often have to be tailor-made for a given study. We have developed a novel tactile stimulator designed to present arbitrary spatio-temporal stimuli to the skin. This tactile display consists of 400 tactors – linear motors – arranged in four planes of 100 motors each. The planes are stacked one on top of another and mounted such that the shafts from each motor converge at a point 48.5 cm below the lowest plane. The shafts consist of a series of stainless steel tubes that are reduced in diameter from the motor to the point of contact with the skin. The contactors are presently configured in a 20 by 20 matrix, 1 cm by 1 cm, but this configuration can be easily modified. Each motor is individually controlled and has a dynamic range from 0 Hz (DC displacement) to over 250 Hz. Vertical displacements can be generated in the range of 2000 microns at 0 Hz to 100 microns at 250 Hz. Patterns generated on the array can be updated every 1ms. The need for such a display has been recognized for a number of years.

With this 400-probe array, complex spatio-temporal patterns are being presented to the skin of both human observers, in psychophysical studies, and to monkeys, in both psychophysical and neurophysiological studies.  This array permits us to generate complex spatio-temporal patterns that simulate the kind of stimulation generated by a finger coming in contact with surfaces. The idea behind the design was to create a display that matched or exceeded the skin’s mechanoreceptive capabilities and permits the generation of spatio-temporal patterns at rates up to 1200 patterns per minute (assuming a typical duration of 50ms per stimulus).