Adventures in the Skin Trade

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The phenomenon that Shinagawa first detected was that the optical properties of an electro-optic crystal vary when there are changes in a weak electric field. When the body's natural electric field interacts with that of the nearest transceiver, for example, distinctive oscillations are transmitted between the fields. Polarized by the oscillations, a tiny laser beam shoots through the RedTacton crystal, and the sensor measures the reflection and converts it to an electrical signal.

First demonstrated at Siggraph by NTT in 2003 under the name ElectAura-Net, the technology has been significantly upgraded in the latest RedTacton prototype.

"We had various problems, including noise and energy consumption, but we have solved one after another," says Sakamoto.

According to Kurt Partridge, who was the principal designer of a recent intra-body networking system at The University of Washington, RedTacton far exceeds the capabilities of any of the existing electrical-sensor-based projects.

"The speed they're getting is very impressive," says Partridge, who is now a researcher at PARC. "It makes the technology competitive with other short-range communications technologies like Bluetooth, Zigbee, and UWB." 

Partridge is looking forward to seeing how well NTT has solved the power-consumption issue.

"Their early prototypes consumed a lot of power;" he says. "Hopefully they've addressed this problem."

Although some potential customers might balk at the idea of their bodies being lit up like a Christmas tree, Sakamoto claims the system is completely safe because no current flows into the body. He also says that the signal integrity is invulnerable to rain, cold, heat, static electricity, or electrical storms.

He does admit, however, despite its infrequence, "data exchanges are sometimes disrupted by electromagnetic waves--radio waves of a particular frequency."

The big breakthough for RedTacton, says Sakamoto, is that it frees the technology from the more severe problems of interference among wireless devices. RedTacton apparently maintains its bandwidth even during simultaneous communications with multiple users. (If true, the group hug could turn into a productivity tool as well as a motivational technique.)

The small transceiver fits comfortably in a shirt pocket and unlike previous systems does not require a direct connection to the skin. The prototype can communicate at 10Mbps with other transceivers on the body, for example, mediating transmission between an MP3 player and a headset, and Sakamoto says it will soon shrink to the size where it can be built-into cell phones and other devices. When connecting beyond the body, the electric field can travel through conductors and dialectrics at a distance ranging from centimeters to meters, depending on the level of conductivity.

NTT is particularly enthusiastic about touch-based personalization applications. For example, the act of sitting in your car seat could instruct seats and mirrors to adjust accordingly or picking up a shared cell phone would instantly make it yours. NTT also envisions touch-based interactive advertising that customizes itself to an individual's profile or smart medicine bottles that would sound an alarm if you try to take the wrong pill.