Our work on tactile displays involves research on characterizing the properties of different actuators used in displays, building and testing different types of tactile displays, evaluating the mechanical properties of skin so as to quantify its responses to vibration and psychophysical studies in which we measure perceptual responses to mechanical stimulation of the skin. We have built displays that can be mounted on the hand, arm, leg or torso and shown that by varying the spatial and temporal properties of vibrotactile stimulation we can create tactile communication systems.
Different actuator technologies have been used to create tactile displays in our lab including liner resonant actuators, voice coil motors, piezoelectric actuators and shape memory alloy actuators. They vary with respect to their bandwidth, response times, capacity to generate different waveform profiles and power requirements. Analyses of their characteristics are important to the design of tactile displays in that they indicate which motors are optimal for specific applications and how the conditions under which the motors make contact with the skin influence their performance (Azadi & Jones, 2014a, 2014b; Jones & Held, 2008).
Tactile displays have been evaluated at different locations on the body including the hand, arm, thigh and torso. We have measured the travelling waves on the skin elicited by vibration of the motors and determined how they vary at different locations and have analyzed how the spatial pattern of activation of motors in a display can be used to provide navigation cues. There are differences among the sites tested and some features of tactile sensory processing such as tactile anisotropies influence the ability to identify tactile patterns at some locations (on the arm) but not others (the back) (Jones et al., 2009; Jones, 2011; Sofia & Jones, 2013).
Tactile patterns that are used to communicate via wearable tactile displays are often called tactons. These patterns can be created by varying the frequency, waveform, intensity and duration of the vibration. Psychophysical studies have indicated that variations in the temporal profile and the location on the body stimulated are the easiest parameters for people to discriminate. Unlike the ear and the auditory system, variations in waveform are much harder to perceive tactually and the frequency and amplitude of vibration are not orthogonal; that is, when the frequency of vibration on the skin changes so too does its perceived amplitude (Azadi & Jones, 2014; Jones, 2011; Jones et al, 2009, 2010; Jones & Sarter, 2008).