MIT creates six-by-four-millimeter ingestible sensor in lab

A thermometer swallowed instead of placed under the tongue would normally raise a practical problem: size. The few ingestible temperature sensors on the market are described as large enough to be difficult to swallow and to risk obstructing the gastrointestinal tract. At MIT, engineers have built a capsule measuring just six by four millimeters, designed to send continuous temperature updates from inside the body.

The device’s core fits on a one-square-millimeter silicon chip. Its oscillator uses leakage current—the small current that flows through a circuit even when it is switched off—and that current changes frequency as the surrounding temperature changes. The circuit can detect temperature within 0.01 °C, according to the MIT work, and can be powered by a 1.55-volt coin cell battery.

The transmission system is designed to save energy. Backscattering lets the sensor’s internal antenna modulate an ultra-high-frequency radio wave sent by an antenna outside the body, then send that signal back. The external antenna interprets the changes in the wave and calculates the temperature, allowing much of the power requirement to sit outside the capsule rather than inside it.

And then, concretely? A clinician could eventually have a continuous internal temperature signal for monitoring infections, including in immunosuppressed patients, rather than relying only on occasional oral or forehead readings. The researchers also point to patients during and after anesthesia, children with fevers, ovulation tracking, athletes, soldiers, and others exposed to extreme temperatures. Those are proposed uses: the available account describes the sensor as a laboratory result, not as a device already deployed in patients.

Saransh Sharma, a former MIT postdoctoral researcher now at the University of Cambridge, is the lead author of the paper on the work. Giovanni Traverso, an MIT associate professor of mechanical engineering, says the ability to monitor infections could help identify them early, particularly among people at higher risk. He and MIT provost Anantha Chandrakasan are senior authors.