Traditionally, temperatures are measured using oral or forehead thermometers, but these methods do not always provide an accurate reflection of core body temperature. Monitoring core temperature internally could simplify the process of identifying illness and assessing the risk of severe fevers. To facilitate this, MIT engineers have created an ingestible sensor capable of providing continuous temperature updates from the gastrointestinal tract.
This sensor, resembling a small blueberry, measures 6 millimeters in diameter and 4 millimeters in height. It is significantly smaller than existing ingestible sensors, which are harder to swallow and may obstruct the GI tract. “A sensor like this allows us to monitor infections and detect them early,” stated Giovanni Traverso, an MIT associate professor of mechanical engineering and gastroenterologist at Brigham and Women’s Hospital. This is especially pertinent for at-risk groups, such as those undergoing chemotherapy or taking immunosuppressive drugs.
Ingestible sensors could also improve temperature accuracy for purposes like fertility tracking and monitoring patients under anesthesia. The study, published in Nature Electronics, lists MIT’s Anantha Chandrakasan and postdoc Saransh Sharma as the senior and lead authors, respectively.
While some ingestible temperature sensors have entered the market, they are typically the size of a multivitamin, making them challenging to ingest and potentially obstructive. Their bulk stems from complex circuits requiring significant power from large batteries.
The MIT team aimed to design a smaller, accurate temperature sensor. “The reason for them to be small is safety,” Traverso explained. The researchers minimized the main components — the temperature-sensing circuit, antenna, and battery — to achieve this.
They developed a custom circuit on a 1-square-millimeter silicon chip, utilizing an oscillator based on leakage current to reduce power consumption. This circuit can measure temperature with a 0.01 degrees Celsius accuracy and uses only about 10 nanowatts, powered by a 1.55-volt coin cell battery.
To lower energy use, the design employs a communication method called backscattering, which shifts most power needs to an external antenna near the sensor. This antenna sends a radio wave that the sensor modulates and returns, allowing the external antenna to determine the temperature.
“We integrated these components — the silicon chip, battery, and antenna — into the smallest ingestible capsule we’ve seen for temperature-sensing,” Sharma noted. The internal antenna provides a temperature reading every second for continuous monitoring.
The researchers see potential uses for the sensor in infection monitoring and patient observation during anesthesia, where body temperature regulation can be disrupted. It could also be useful at home for tracking fevers in children or as an ovulation marker for fertility.
Tests on animals under anesthesia indicated that the sensor accurately transmitted temperature data, even when the animals were awake and moving. The team is working on integrating additional sensors for vital signs like heart rate, with plans for clinical trials in the coming years.
If successful, Traverso suggests that these sensors could replace traditional thermometers, offering a precise and convenient way to monitor temperature. “I think this could replace all thermometers because it’s the most accurate way of taking temperature,” he said. Other contributors to the paper include Yubin Cai, Injoo Moon, Zhenming Yang, and several others.
The research received funding from the 711th Human Performance Wing, DARPA, and ARPA-H, with the authors noting that the views expressed do not represent official U.S. government policies.
Original Source: news.mit.edu
