In recent years, we've heard about navigational systems which guide pedestrians via vibrating actuators in their shoes. The FeetThrough system takes a different and reportedly better approach, by actually shocking the soles of the feet.
Currently in proof-of-concept form, FeetThrough is being developed by the University of Chicago's Assoc. Prof. Pedro Lopes and electro-communications PhD student Keigo Ushiyama. According to them, systems which utilize arrays of vibrating actuators (aka vibrotactile stimulation) have some definite limitations.
First and foremost, when those actuators are activated, the user can't also feel the underlying terrain through the soles of their shoes. This is an important consideration, as feeling the contours of the surfaces which we're walking on is essential to maintaining our balance.
Additionally, while each individual actuator may be located adjacent to a specific point on the sole of the foot, its vibrations can be felt over a wider area. So in other words, such systems' "tactile resolution" (or whatever you want to call it) isn't very high.
Finally, because the actuators are typically built into insoles or other footwear, the technology can't be utilized in barefoot scenarios such as VR gaming.
That's where FeetThrough comes in.
The setup consists of two thin, flexible arrays of 60 electrodes, each array covering the sole of one foot from the ball to the heel. These arrays can be adhered directly to bare skin, they can be placed in the insoles of shoes, or they can be integrated into special socks. An electronics module is connected to each array.
Users are made to feel patterns on the underside of each foot (such as left- or right-turn arrows) by delivering mild electrical shocks through specific electrodes in each array. And importantly, because the arrays are just one tenth of a millimeter thick, those users can still also feel the surfaces they're walking or standing on.
In lab tests, 12 participants were tasked with identifying both stepped-upon physical shapes and virtual shapes – the latter were separately delivered via vibrotactile and electrotactile (FeetThrough) stimulation. It was found that when electrotactile stimulation was used, the test subjects were significantly better at identifying both the physical and virtual shapes.
That having been said … does it hurt?
"All the sensations we used in this work are calibrated per participant so that they feel good," Lopes told us. "We can do that mostly by adjusting the amplitude so that it generates a nice touch sensation as opposed to a strong pinching sensation that becomes closer to pain thresholds of the skin."
He added that the sensations still do feel different than typical touches, however, so users are able to differentiate between navigational cues and feelings of pressure produced by the terrain.
A paper on the research will be presented at the ACM Symposium on User Interface Software and Technology later this month. You can see the FeetThrough system in use, in the video below.
Source: University of Chicago Human Computer Integration Lab
