MIT engineers develop tiny ingestible temperature sensor that transmits continuous updates

Existing ingestible temperature sensors are so large that they are difficult to swallow and risk obstructing the gastrointestinal tract. The new device fits its circuit on a one-square-millimeter silicon chip. Researchers built an oscillator based on leakage current, the small current that flows through a circuit when it is off, and its frequency changes with the temperature of the chip’s surroundings. The system can detect temperature differences of 0.01 °C.

The sensor runs on a 1.55-volt coin cell battery. A technique called backscattering further reduces energy use by shifting most power requirements to an antenna outside the body. That antenna emits an ultra-high-frequency radio wave, which an antenna within the sensor modulates and sends back. The external antenna then calculates the temperature from the changes in the radio wave.

Saransh Sharma, a former MIT postdoc now at the University of Cambridge and lead author of the paper, called the capsule “the smallest ingestible capsule that we have seen for temperature-sensing paradigms.” The researchers say the sensor could be used to monitor infection, observe patients during and after anesthesia, track fevers in children, help mark ovulation, and watch athletes, soldiers, or others exposed to extreme temperatures.

Giovanni Traverso, an associate professor of mechanical engineering and a senior author, said, “A sensor like this gives us the ability to monitor infections and identify them early,” adding that this is particularly relevant for at-risk populations such as immunosuppressed people. He hopes the device could eventually replace other thermometers for everyone. MIT provost Anantha Chandrakasan is the other senior author of the paper.