Real-time monitoring of our muscles, nerves, and organs without living inside an MRI machine sounds like a fantasy awaiting some future generation of science. But University of California, Berkeley engineers cracked the code to monitoring from the inside. The key to the breakthrough hinged on working around the limitations of radio waves within the body. Radio waves inside the body lose strength quickly so the only way to send or receive signals to implanted devices, particularly if in deep, entails cranking up the power to potentially harmful levels.
In 2013, a team led by Michel Maharbiz, an associate professor of electrical engineering and computer sciences, discovered the solution: ultrasound. “Our first study demonstrated that the fundamental physics of ultrasound allowed for very, very small implants that could record and communicate neural data,” said Maharbiz. Ultrasound provides both the power for and the means to read measurements from tiny implanted sensors. Since 2013, Maharbiz and his students have worked at shrinking suitable sensors.
Working with rats, the team implanted what they refer to as “neural dust” in muscles and peripheral nerves. The latest version of the neural dust particles measure 3 by 1 by 0.8 mm (0.12 x 0.4 x 0.3 inches). Eventually, the team hopes to get closer to the theoretical limit of 50 microns (2 thousands of an inch, or half the width of a human hair). The smaller size would provide sensors for brain and central nervous system applications, and allow the sensors to rest near just a few nerve axons.
The neural dust’s current size, however, suits applications with the peripheral nervous system such as with bladder control. The UC-Berkeley’s neural dust creates category of “electroceuticals,” battery-less sensors that can stimulate nerves and muscles for a wide range of treatments and accommodations. Neuroscientist Jose Carmena, a professor of electrical engineering and computer sciences on the team wrote, “Now that you have a reliable, minimally invasive neural pickup in your body, the technology could become the driver for a whole gamut of applications, things that today don’t even exist.“
