Electrodes attached to legs can guide people wherever you want them to go via an app. Welcome to the bizarre world of electro-stimulation

Where are you going?

For a few days last summer, a handful of students walked through a park behind the University of Hannover in Germany. Each walked solo, but followed the same route as the others: made the same turns, walked the same distance. This was odd, because none of them knew where they were going.

Instead, their steps were steered from a phone 10 paces behind them, which sent signals via bluetooth to electrodes attached to their legs. These stimulated the students’ muscles, guiding their steps without any conscious effort.

Max Pfeiffer of the University of Hannover was the driver. His project directs electrical current into the students’ sartorius, the longest muscle in the human body, which runs from the inside of the knee to the top of the outer thigh. When it contracts, it pulls the leg out and away from the body. To steer his test subjects left, Pfeiffer would zap their left sartorius, opening their gait and guiding them in that direction.


Pfeiffer hopes his system will free people’s minds up for other things as they navigate the world, allowing them to focus on their conversation or enjoy their surroundings. Tourists could keep their eyes on the sights while being imperceptibly guided around the city.

Acceptance may be the biggest problem, although it is possible that the rise of wearable computing might help. Pfeiffer says the electrode’s current causes a tingling sensation that diminishes the more someone uses the system. Volunteers said they were comfortable with the system taking control of their leg muscles, but only if they felt they could take control back.

One of the students compared the feeling to cruise control in a car, where the driver can take control back when they want it. “Changes in direction happened subconsciously,” said another.

Pfeiffer steered students manually, but the plan is to build the mechanism into other apps. Navigation apps, for instance, could steer people along their route automatically, meaning they never have to look at their phone or think about where they are going.

“When I use Google Maps and I navigate somewhere, I am always pulling my mobile out of my pocket to check,” he says. “We want to remove this step out of the navigation process so you just say ‘I want to go there’, and you end up there.”

The system could also be used to direct crowds, not just individuals. “Imagine visitors to a large sports stadium or theatre being guided to their place, or being evacuated from the stadium in the most efficient way in the case of an emergency,” the team write in a paper that will be presented at the CHI conference in Seoul, South Korea, next week.

Evan Peck of Bucknell University in Pennsylvania says Pfeiffer’s system will stop us being chained to our smartphones. “We’re developing all this really wonderful tech and almost all of it demands our attention,” he says. “We build a navigation system, but then we have to stare at it.”

“Their goal is letting you use your attention on what you want to use it on,” says Peck. “It’s in your hands now.”

Hand-hacking teaches new tricks Tweaking a person’s muscles using electrodes (see main story) is precise enough that a computer can now guide us through unfamiliar tasks. Pedro Lopes and Patrick Baudisch at the Hasso Plattner Institute in Berlin, Germany, have designed an electro-stimulation system attached to arm muscles that tells the wearer how to use an object. A can of spray paint fitted with an RFID tag that talks to the system can tell people to shake it before use, say, while a knife tells people how to cut an avocado. It will be presented at the CHI conference in Seoul next week. “We’re moving away from processing things with our eyes and brain towards feeling things,” says Baudisch.

This article appeared in print under the headline “Human cruise control”