Nakamura Lab at Tohoku University has developed a tablet-size "swallowable" thermometer.
Normally, body temperature is measured on the body surface such as under the arm. But the new thermometer can 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 one's "biological clock (rhythm)," according to Nakamura Lab.
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 or clinic.
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 can 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 the 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.
The thermometer moves from the stomach to the duodenum in 30 to 60 minutes. But it is charged while moving and can operate for about 10 hours, according to Nakamura Lab.
The temperature sensor embedded in the swallowable thermometer measures deep body temperature every 30 to 60 minutes and wirelessly transmits measured data. For wireless data transmission, it uses the 10MHz frequency band, which is not absorbed by the human body and has a high transmission efficiency, Nakamura Lab said.
Component cost of 100 yen or less at time of volume production
In addition to safety, Nakamura made special efforts to make the swallowable thermometer by using "withered" technologies to lower costs.
"We expect that the component cost at the time of volume production will be ¥100 or less," he said.
The swallowable thermometer consists of four components: a temperature sensor, wireless communication function, customized chip and capacitor. For the manufacturing of the customized chip, a 0.6μm-process withered CMOS technology was used.
The significance of being able to easily measure an accurate deep body temperature is great. The thermometer can be used for (1) knowing ovulation cycles, which usually causes a large margin of error, (2) measuring the fatigue degrees of athletes, (3) preventing heat strokes and hypothermia, etc. Also, by knowing a biological clock, it can maximize athletic performance and adjust jet lag.
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