Researchers from Caltech have developed a prototype of a medical device that could be used in “smart pills” to diagnose and treat diseases. The key to this new technology is that its location can be precisely identified within the body, which has been challenging in the past.
"The dream is that we will have microscale devices that are roaming our bodies and either diagnosing problems or fixing things," said Azita Emami, the Andrew and Peggy Cherng professor of electrical engineering and Medical Engineering and Heritage Medical Research Institute investigator, who co-led the research along Mikhail Shapiro, assistant professor of chemical engineering and Heritage Medical Research Institute investigator. "Before now, one of the challenges was that it was hard to tell where they are in the body."
The silicon-chip device, called ATOMS (addressable transmitters operated as magnetic spins), borrows from the principles of magnetic resonance imaging (MRI) where the location of atoms in a patient’s body is determined using magnetic fields. The micro devices would be located in the body through magnetic fields. Rather than relying on the body’s atoms the chips contain a set of integrated sensors, resonators and wireless transmission technology that allow them to mimic the magnetic resonance properties or atoms.
"A key principle of MRI is that a magnetic field gradient causes atoms at two different locations to resonate at two different frequencies, making it easy to tell where they are," said Shapiro. "We wanted to embody this elegant principle in a compact integrated circuit. The ATOMS devices also resonate at different frequencies depending on where they are in a magnetic field."
"We wanted to make this chip very small with low power consumption, and that comes with a lot of engineering challenges," said Emami. "We had to carefully balance the size of the device with how much power it consumes and how well its location can be pinpointed."
The devices are still preliminary but one day they could serve as miniature robotic wardens of the body, monitoring patient’s gastrointestinal tract, blood or brain. The devices could measure factors that indicate the health of a patient like pH, temperature, pressure or sugar concentrations, and then relay that information to doctors. Or the devices could be used to release drugs into the system.
"You could have dozens of microscale devices traveling around the body taking measurements or intervening in disease. These devices can all be identical, but the ATOMS devices would allow you to know where they all are and talk to all of them at once," said Shapiro. He compares it to the 1966 sci-fi movie Fantastic Voyage, in which a submarine and its crew are shrunk to microscopic size and injected into the bloodstream of a patient to heal him from the inside--but, as Shapiro said, "Instead of sending a single submarine, you could send a flotilla."
"This chip is totally unique: there are no other chips that operate on these principles," said Monge. "Integrating all of the components together in a very small device while keeping the power low was a big task."
The final prototype chip was tested on and proven to work in mice. It has a surface area of 1.4 square millimeters, 250 times smaller than a penny. It contains a magnetic field sensor, integrated antennas, wireless powering device and a circuit that adjusts radio frequency signal based on the magnetic field strength to wirelessly relay the chip’s location.
"In conventional MRI, all of these features are intrinsically found in atoms," said Monge. "We had to create an architecture that functionally mimics them for our chip."
While the prototype chip can relay location in the body, the next step is to build one that can relay location and sense body states.
"We want to build a device that can go through the gastrointestinal tract and not only tell us where it is but communicate information about the various parts of the body and how they are doing."
A paper on this research was published in the September issue of Nature Biomedical Engineering