Researchers 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 is that its location can be precisely identified within the body — something that previously proved challenging.

The addressable transmitters operated as magnetic spins (ATOMS) are silicon-chip devices that 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 allows them to mimic the magnetic resonance properties of atoms.

Illustration of an ATOMS microchip localized within the gastrointestinal tract. The chip, which works on principles similar to those used in MRI machines, is embodied with the properties of nuclear spin. (Ella Marushchenko/ Caltech)

With MRI, a magnetic field gradient causes atoms at two different locations to resonate at two different frequencies, making it easy to determine their location. This principle is used in a compact integrated circuit in the ATOMS devices, which also resonate at different frequencies, depending on where they are in a magnetic field.

The devices could be used to monitor a patient's gastrointestinal tract, blood, or brain. They also could measure factors that indicate the health of a patient — such as pH, temperature, pressure, and sugar concentrations — and relay that information to doctors. The devices could even be instructed to release drugs.

Dozens of the microscale devices could travel through the body taking measurements or intervening in disease. The devices can all be identical, but the ATOMS devices would signal where they are and enable them to be controlled simultaneously.

The final prototype chip 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.

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