A research group from the Graduate School of Engineering at Tohoku University has developed a non-invasive means of detecting the signals from "digital pills," a type of medication often used by doctors to monitor a patient's adherence to a medication regime. When swallowed, the circuit sends out a small signal that can be detected from outside the body.

The breakthrough will be presented at the 70th Annual Conference on Magnetism and Magnetic Materials on March 30, 2025.

"Until now, digital pills required a skin patch to pick up signals from inside the body," points out Takahide Kubota, a specially appointed associate professor at Tohoku University's Graduate School of Engineering and co-leader of the study. "However, this patch often causes skin irritation."

To overcome these problems, the team created a non-contact detection system. They used a quantum spin sensor, called a TMR sensor, to detect the tiny magnetic fields from the pill. The experiment showed that the sensor could accurately detect these signals through saline water, even without using a magnetic shield.

The detected magnetic signals perfectly matched the voltage signals measured by electrodes, confirming that both carried the same digital information. This means that the new system can track medication intake without touching the skin.

"Our method is completely non-invasive and skin-friendly," Yasuo Ando, also a professor at the Graduate School of Engineering who co-led the paper with Kubota. "We hope it will make medication monitoring more comfortable and help people follow their prescriptions safely."

The team believes that this technology could be used not only in healthcare but also in energy-efficient electronics. Detecting very small magnetic fields could improve how we measure and manage electric currents in smartphones and batteries, helping to design longer-lasting devices.

This study was conducted in collaboration with Otsuka Pharmaceutical Co. Ltd, and Spin Sensing Factory Inc. The work was carried out at the Advanced Spintronics Medical Engineering Laboratory, supported by Otsuka Pharmaceutical Co. Ltd and Spin Sensing Factory Inc.

Publication Details:

Title: Magnetic Field Detection from an Ingestible Device using a Tunnel Magnetoresistance Sensor
Authors: Takahide Kubota, Hiroshi Wagatsuma, Kosuke Fujiwara, Motoki Endo, Takayuki Hojo, Makoto Ishida, Nobukazu Nakasato, Hiroki Ono, Hayato Fukushima, Seiji Kumagai, Hitoshi Matsuzaki, Kazuma Yokoi, Suguru Oyagi, Rei Otsuka, Ikuro Yamane, Dollyrey Canlas, Jaleh Komaili, Sumukh Pathare, Jonathan Withrington, Todd Thompson, Junichi Jinno, Koji Onishi, and Yasuo Ando
Conference: The 70th Annual Conference on Magnetism and Magnetic Materials

Press release in Japanese