Nakamura Lab at Tohoku University developed a tablet-size "swallowable thermometer."

Normally, body temperature is measured on body surface such as under the arm. But the new thermometer enables to easily measure a "deep body temperature (basal body temperature)," which offers more stable, more accurate measured values, at a low cost. As a result, it becomes possible to know "biological clock (rhythm)," according to Nakamura Lab.

The "swallowable thermometer" developed by Nakamura Lab at Tohoku University. It was unveiled at Semicon Japan 2018, a trade show for the semiconductor industry, which took place from Dec 12 to 14, 2018. (source: Tohoku University)

The importance of deep body temperature, which represents health conditions (internal life-supporting functions), is widely known. But it cannot be measured on a daily basis because it is in the body. The most common way to measure deep body temperature is to measure "rectal temperature" by inserting a thermometer into the anus. However, it is not a convenient way because it requires the patient to go to a hospital, etc.

In view of this, Tsutomu Nakamura, a specially-appointed professor of the Center for Innovation and Business, the Head Office of Enterprise Partnerships, Tohoku University, developed the safe, low-cost swallowable sensor that enables to measure deep body temperature at the time of sleeping (at rest). The diameter of the sensor is 9.16mm. It does not contain any substance that is harmful to human body.

The swallowable thermometer generates electricity in the stomach, using the same principle as a so-called "Lemon battery." The Lemon battery utilizes a phenomenon in which, when two kinds of metals having different ionization tendencies are immersed in electrolytic solution, they generate an electromotive force.

In the same way, the new thermometer can generate power because an electric potential difference is produced between magnesium (Mg) and platinum (Pt) electrodes under the strong acid environment in the stomach. And electricity generated is stored in the capacitor of the thermometer.

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