The Fall issue of MIT's Spectrum magazine spotlights a number of MIT faculty who work with nanotechnology. The topic of nanotechnology is introduced with the opening: "Nanotechnology’s impact will one day rival that of electricity, transistors, antibiotics, and the Internet — thanks in part to MIT research." Ian Waitz, Dean of MIT's School of Engineering closes this nano-introduction: "I find it amazing that we’re engineering things at that scale, and then using them to solve very challenging problems. I’m excited about the prospects for the ‘world of the small.’"
EECS associate professor Joel Dawson, is one of the eight MIT faculty whose work is featured in this issue.
Joel Dawson is working on an inexpensive sensor the size of a grain of rice that could be implanted in patients with Parkinson's disease to monitor their tremors. Photo: Len Rubenstein
Miniscule Medical Monitors
by Elizabeth Thomson
When Joel Dawson was 12, he was fascinated by MIT Professor Emeritus Rodney Brooks’ insect robots that were then in the news. "I thought, 'I’ve got to go to the place where they would work on things like that,’" he says.
Now Dawson, who earned an MIT bachelor’s degree in 1996 and a master’s in 1997, both in electrical engineering, is an associate professor in the same department Brooks called home. And he’s putting his own stamp on the field of electrical engineering and computer science. Among his projects is an inexpensive sensor the size of a grain of rice that could be implanted in patients with Parkinson’s disease to monitor their tremors. Individual components in such a sensor are on the nanoscale, or billionths of a meter.
Patients with Parkinson’s visit a doctor regularly to report on the general state of their tremors. Clinicians, however, "would love to complement that kind of feedback with the more objective data possible by wearing some kind of monitoring device," Dawson says. Such data could allow better tracking, say, of disease progression, or the efficacy of drugs.
The technology for such monitoring exists, but the resulting device would be relatively large — roughly the size of a man’s watch. "The downside is that now this person has to wear a big medical device all the time. And it’s a reminder that they’re ill," says Dawson, the Mark Hyman, Jr. Associate Professor of Electrical Engineering. As a result, unless such a monitor is critical to their health, a patient often won’t wear it. Similarly, the device must also be easy to use.
"Our work in nanotechnology is to build medical monitors that are user-friendly and won’t have a major impact on a person’s life," Dawson says. Depending on what needs monitoring, the device could, for example, be implanted in the body with an outpatient procedure, attached to a fashionable watch, or even sewn into clothing.
The sensor would be powered by an energy storage device known as an ultracapacitor. Because it can be charged over and over without wearing out, it wouldn’t have to be replaced, in contrast to even the best rechargeable batteries. Further, a device powered this way could be almost instantly recharged with a simple tap to a charging unit.
The downside, though, is that unlike a battery, which will hold its energy output at a steady rate until it dies, an ultracapacitor’s energy output drops continuously as it is used. "And that behavior makes it difficult to design the electronic circuits that use that energy to store and transmit sensor data," Dawson says.
To circumvent the problem, he and his team developed a novel system. "Rather than rely on a single ultracapacitor, we take an array of them stacked strategically so that as the energy is drained out of [each] capacitor bank, we keep the voltage high," he says. He and his team have created a prototype chip containing the electronic circuits that can interface with that system. Ultimately they would like to integrate ultracapacitors and circuits on the same chip, making the system much more compact.
Dawson says that his top goal is to create a medical device that’s easy for a patient to use. That, he says, "is emerging as the critical thing about medical electronics."