The Wrist Bone’s Connected to the Cell Phone

By Jade Boyd

Michael Liebschner and Lin Zhong make no bones about rattling cages—rib cages, that is. The two engineering faculty members are involved in joint research to develop a new technology that lets mobile electronic devices communicate by sending vibrations through bones.

“Cell phones have vibrators in them now, and many of the newer models have sensors that could be used to receive our signals, so it’s feasible to think of the devices we are already carrying as a platform for this technology,” said Zhong, assistant professor of electrical and computer engineering.
This explains why Microsoft awarded Liebschner and Zhong a grant to develop OsteoConduct, the technology the two invented last year. OsteoConduct transmits digital information through bones using acoustic sound patterns. The sounds can be created by anything that vibrates.

In the lab, the researchers use hand-held and bench-mounted gadgets. The vibrations can be imperceptible in some applications, such as health monitoring or simple data exchange, and perceived in others. For example, a patient wearing a drug-release system might benefit by sensing when drugs are administered.

“Microsoft is interested in computing applications related to both health care and mobile devices, and this hits both of those,” said Liebschner, assistant professor of bioengineering.

The idea for OsteoConduct came after Zhong heard Liebschner present results from his lab at last fall’s Texas Instruments Innovation Fund Day, a conference highlighting TI-funded research at Rice. Liebschner described the development of a new hand-held system for diagnosing osteoporosis with low-level sound waves. Zhong, sitting in the audience, thought immediately of work he was doing.

Teeth Clicks

During a research internship just before joining Rice, Zhong worked with several Microsoft researchers who devised solutions to improve voice recognition by filtering out the sounds created when people click their teeth together during speech.

“At the time, I thought, ‘This is information that they are throwing away,’ and I wondered if there might be another way to use it,” Zhong said. After joining Rice, Zhong and graduate student Tamer Mohamed built a hands-free method of using teeth clicks to control a computer.

At the TI conference, Zhong asked Liebschner if his findings suggested that the sound of teeth clicks might travel through a person’s skeleton. Liebschner thought they might, and the two agreed to test the idea.

Liebschner said one of the most exciting discoveries about this research has been just how clearly sound travels through bone. In one of the earliest tests, a signal from the wrist was clearly detected at the hip, having traveled the length of the arm and spine.

“We were all surprised to see these signals propagate through 20 or more joints,” Liebschner said. “It worked much better than we’d anticipated for the power levels we used.”

Unique Skeletal Identification

Liebschner said one probable reason the discovery went unnoticed for so long is the variability of human bone tissue. Sound vibrations are commonly used to test the skeletal structures of buildings after earthquakes, but no two people have exactly the same acoustic pattern in their bones. However, Liebschner said, this variability has an upside, too.

“Because every person has a unique acoustic signature in their bones, we believe we can develop that for security authentication,” Liebschner said. “For example, you might grab a door handle in a secure facility, and it would only allow you inside if it recognized your profile. The acoustic signature of the skeleton is thought to be more secure than fingerprints or retina scans.”

Other applications Zhong and Liebschner are considering include hands-free operation of mobile phones and other devices, secure data transmission, health monitoring and diagnostics, and communication with implantable transducers.

Bioengineering graduate student Michael Cordray and undergraduate Mimi Zhang are co-inventors of the technology. Researchers include electrical and computer engineering graduate students Brett Kaufman and Tamer Mohamed and bioengineering graduate students Dania El-Daye and Nick Tobaoda.