30 October 2009—The human gateway to the electronic world is mostly through our eyes and ears. But devices that connect through our sense of touch have been developed for the fingertips, the chest, the back, and even the tongue. Now researchers in Mexico have come up with a device to communicate via your feet, and a collaboration between a Dutch organization and General Motors has tested a way to communicate potentially vital driving information through none other than your rear end.
The point of these new tactile devices is to develop touch-sensitive applications for virtual reality, gaming, robotics, rehabilitation, navigation, and assistance for the blind or visually impaired, among others things.
The shoe dropped at the recent IEEE/RSJ International Conference on Intelligent Robots and Systems. Ramiro Velazquez, an assistant professor in the Mechatronics and Control Systems Lab at Mexico's Panamerican University, presented his computer-sole interface, which will be worn inside a shoe in its final version. It's the first device to stimulate the bottom of the feet to convey information, rather than to enhance sensation. The goal of his study, Velazquez says, was to answer the question, "Are we capable of understanding information through our feet?"
The answer, it turns out, is yes.
His group chose to stimulate an area of the foot that has a high concentration of receptors for texture and vibration sensing—around where the arch and the ball of the foot meet, along the outer edge of the sole. The researchers arrayed four rows of four miniature vibrating motors of the type used in cellphones, available commercially for US $10, in the shoe insert. Each of these 16 actuators could be activated independently and at different vibrating frequencies to transmit signals, meant to communicate directions and patterns, to 20 research subjects in their study.
First, the researchers tested whether people could understand "dynamic directions," or signals moving in certain directions on the bottom of the feet, while the subjects simply sat still. The researchers matched cardinal directions to patterns on the shoe insert by vibrating rows and columns of the actuators one after another. They vibrated heel row to toe row, for example, to indicate north, or forward, and reversed the direction from toe row to heel row to indicate south, or backward.
The researchers also tested the subjects' ability to perceive geometric shapes made by the vibrating actuators; patterns of vibration, like the alerts for calls or text messages on cellphones; and navigation cues using the dynamic directions as before but this time while the subjects were walking blindfolded around obstacles in a room. They found that people were best at sensing directions and recognizing patterns. In the navigation test, completed by five of the original 20 subjects, four tested well. One got pretty turned around, though even he eventually made it through the obstacle course.
Certain information is just not easily discernible when transmitted via foot communication, Velazquez found. The test subjects had difficulty determining geometric shapes, such as a line, a circle, or a square. Velazquez explains that because vibrations expand throughout the skin, very specific geometric information—such as a diagonal line—is difficult to distinguish.
Still, humans can glean a lot from the soles of their feet. Now that his group has seen what's possible, Velazquez hopes they can create "a new tactile language for the feet" that you'd learn just like any other language.
Carnegie Mellon Robotics Institute professor Mel Siegel says that although the device is "clearly an early prototype," it shows the promise of "really doing something useful," like aiding the visually impaired. It also comes at a time when our primary senses for navigation and mapping the world around us—our eyes and ears—are overloaded, Siegel points out. "Everyone talks about sensory overload," he says. But if you could use this "other modality"—touch—you might be able to take in important information without competition in the same arena from other visual or audio signals, Siegel says, although experiments would need to prove that hypothesis.