MIT engineers have shrunk the ingestible thermometer to something you’d barely notice swallowing. The new capsule measures just six by four millimeters—a fraction of the size of existing ingestible sensors, which are bulky enough to risk obstructing the GI tract. Inside, a one-square-millimeter silicon chip runs an oscillator based on leakage current, the tiny trickle of electricity that flows through a circuit even when it’s off. That current’s frequency shifts with surrounding temperature, letting the chip detect changes within 0.01 °C.
The power story is where it gets clever. A 1.55-volt coin cell battery keeps things running, but backscattering does the heavy lifting on energy. An external antenna outside the body emits an ultra-high-frequency radio wave, which the sensor’s internal antenna modulates and bounces back. The external reader then decodes those changes to calculate temperature. By offloading most of the power burden to the outside antenna, the capsule sips energy instead of guzzling it.
Saransh Sharma, a former MIT postdoc now at the University of Cambridge and lead author on the paper, calls it “the smallest ingestible capsule that we have seen for temperature-sensing paradigms.” Giovanni Traverso, an associate professor of mechanical engineering and senior author along with MIT provost Anantha Chandrakasan, sees early infection detection as a killer app. “A sensor like this gives us the ability to monitor infections and identify them early,” he said. “That’s very relevant, particularly for at-risk populations like people who are immunosuppressed.”
The use cases stretch well beyond hospitals. Monitoring patients during and after anesthesia, tracking fevers in children, marking ovulation, and watching athletes or soldiers exposed to extreme temperatures all made the researchers’ list. Traverso’s long-term ambition is bigger: replacing conventional thermometers entirely. Whether that happens depends on cost, regulatory clearance, and whether doctors trust a swallowed chip over a temporal artery scan. But the precision here—0.01 °C on a battery that fits inside a pill—suggests the old glass thermometer’s days are numbered.
