In recent years, we've heard about navigation systems that guide pedestrians via vibrating actuators in shoes. The FeetThrough system takes a different, and reportedly better, approach by actually vibrating the soles of your feet. Currently, FeetThrough is in the proof-of-concept stage and is being developed by Assoc at the University of Chicago. Professor Pedro Lopes and electronic communications doctoral student Keigo Ushiyama. According to them, systems utilizing arrays of vibrating actuators (also known as vibrotactile stimulation) have some clear limitations.
First and most importantly, when these actuators are activated, the user also cannot feel the terrain underneath through the sole. This is an important consideration because feeling the contours of the surface we walk on is crucial to maintaining balance.
Additionally, while each individual actuator may be located near a specific point on the sole of the foot, its vibrations can be felt over a wider area. In other words, the "tactile resolution" (or whatever you want to call it) of such a system isn't very high.
Finally, since the actuators are usually built into insoles or other footwear, the technology cannot be used in barefoot scenarios such as VR games.
This is where FootThrough comes into play. The device consists of two thin, flexible arrays with 60 electrodes each, each covering the sole of one foot, from ball to heel. These arrays can be adhered directly to bare skin, placed in insoles, or integrated into special socks. Each array is connected to an electronics module.
By delivering mild electric shocks through specific electrodes in each array, the user can feel patterns on the bottom side of each foot (such as a left or right turn arrow). Importantly, because the array is only a tenth of a millimeter thick, these users can still feel the surface they are walking or standing on.
In laboratory tests, 12 participants were tasked with identifying physical and virtual shapes they stepped on - the latter delivered via vibrotactile and electrotactile (foot-through) stimulation respectively. It was found that test subjects were significantly better at recognizing physical and virtual shapes when electrotactile stimulation was used.
That being said... does it hurt?
"All the senses we use in this work are calibrated for each participant so that they feel good," Lopez told us. "We can do this primarily by adjusting the amplitude so that it creates a nice tactile sensation rather than a strong sensation closer to the skin's pain threshold."
However, the sensation is still different from typical touch, so users are able to differentiate between navigation cues and the pressure sensation created by the terrain, he added.
A paper on the research will be presented later this month at the ACM Symposium on User Interface Software and Technology.