Unique microchip tracks smart pills and biosensors

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New technology gives tracking capabilities to medical devices inside the body. That is critical for the function of biosensors and smart pills.

Researchers at Caltech have developed a prototype miniature medical device that could ultimately be used in “smart pills” to diagnose and treat diseases. A key to the new technology—and what makes it unique among other microscale medical devices—is that its location can be precisely identified within the body, something that proved challenging before.

Called ATOMS, which is short for addressable transmitters operated as magnetic spins, the new silicon-chip devices borrow from the principles of magnetic resonance imaging (MRI), in which the location of atoms in a patient’s body is determined using magnetic fields. The microdevices would also be located in the body using magnetic fields—but rather than relying on the body’s atoms, the chips contain a set of integrated sensors, resonators, and wireless transmission technology that would allow them to mimic the magnetic resonance properties of 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. The researchers wanted to embody this elegant principle in a compact integrated circuit. ATOMS devices also resonate at different frequencies depending on where they are in a magnetic field.

New chip tracks biosensors
The ATOMS device has a surface area of 1.4 square millimeters, 250 times smaller than a penny. It contains a magnetic field sensor, integrated antennas, a wireless powering device, and a circuit that adjusts its radio frequency signal based on the magnetic field strength to wirelessly relay the chip’s location. (Image: Caltech).

The scientists wanted to make this chip very small with low power consumption, and that comes with a lot of engineering challenges. They 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 could one day serve as miniature robotic wardens of our bodies, monitoring a patient’s gastrointestinal tract, blood, or brain. They could measure factors that indicate the health of a patient—such as pH, temperature, pressure, sugar concentrations—and relay that information to doctors. Or, the devices could even be instructed to release drugs.

Biosensors take measurements

You could have dozens of microscale devices and biosensors -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. The researchers compare 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, 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. Integrating all of the components together in a very small device while keeping the power low was a big task. The final prototype chip, which was tested and proven to work in mice, has a surface area of 1.4 square millimeters, 250 times smaller than a penny. It contains a magnetic field sensor, integrated antennas, a wireless powering device, and a circuit that adjusts its 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. Ther researchers had to create an architecture that functionally mimics them for our chip.

 

microchip for tracking smart pills (Image: Caltech)

An ATOMS microchip localized within the gastrointestinal tract. (Image: Caltech)