Transfer Properties Of Touch Elicited Waves: Effect Of Posture And Contact Conditions

During haptic interaction with touched objects, contact with the skin elicits mechanical signals that propagate rapidly to distances removed from the location of contact. Prior research has shown that these touch elicited mechanical signals travel predominantly as waves, and during manual touch, reach distances spanning the entire hand. While the structure in these signals is well preserved across distance, it is unknown how the propagation of these signals from the contact locus to other areas of the hand or finger depend on posture or contact conditions. To address this, we measured empirical transfer functions from a contacting plate that stimulated the fingertip to other sites on the finger, and analyzed the dependence of the corresponding frequency domain transfer functions on location, posture, and contact forces. The results suggest that the frequency and spatial dependence of these transfer functions varied consistently, and encoded contact conditions and relative contact location. Greatest variation was observed in the low or high frequency ranges of vibrotactile sensation, and at large distances from the contact surface. In contrast, mechanical information in the frequency range from 100 to 200 Hz was well preserved at large distances, and across conditions, indicating that tactile information in this frequency range is transmitted to other finger locations in a manner that is relatively invariant to the conditions and location of touch contact. The results may refine current understanding of the biomechanics of cutaneous wave propagation in the hand, may hold implications for understanding information content in touch-related cutaneous waves, and could hold inform the design of tactile displays worn on the skin.