Technology between hearing aid, temperature and pulse measurement

Foto: Sensor in the ear

Their small invention is about wireless data transfer in everyday life, which measures body temperature and pulse rate at the same time – all in the size of a hearing aid.

The idea arose from the research work done within the scope of a doctoral thesis. The goal of the student at the TUM Chair for Real-Time Computer Systems was to develop a sensor that can wirelessly gather and send data of a person’s body.

“We wanted to develop a sensor that wouldn’t bother the user and that is inconspicuous and mobile at the same time,” explains Doctor Johannes Kreuzer. He designed a measurement device, that is similarly small in size to a hearing aid, but measures the body temperature and the pulse in the ear and nonetheless works reliably during different strong movements, for example while doing sports. For this, Kreuzer explains, the temperature sensor is simply placed in the ear. This way, the performance of athletes is also meant to be rated, since the core body temperature during athletic training shows the performance status of a person.

But what makes the ear so attractive for the placement of a sensor? The graduates very quickly realized that the conditions are very stabile for measuring at this body part. “Nowhere else on the body can the body temperature be non-invasively measured as well as in the ear, “ Kreuzer adds.

Although there is the possibility of measuring temperature via a rectal sensor, in the mouth or via a stomach tube, these would admittedly be less attractive methods. Especially for people that do sports and test functional clothing, now measuring can occur in a much less complicated fashion. According to the TUM researchers, until now there was no way of measuring the temperature underway and comfortably – and that’s why it was rather left well alone. Under normal conditions, the newly developed measuring device detects the body temperature without constricting the worker or athlete.

Technically, the body temperature and pulse measuring device resembles a hearing aid, since developers have conveyed the main principle of construction to the sensor technology. Kreuzer explains: “The measuring device is worn behind the ear pinna and leads into the ear canal. In addition there is a small device that is located in the ear pinna to ensure the best possible hold. That’s why the sensor also works in difficult situations.“ However, the scientist does not want to reveal all of the specifics, since the competition never sleeps.


Photo: Sensor shown on a hand

Difficult situations, in which the sensor has proven itself as being robust, are testing as well as sports activities. The sensor already has the first tests behind it, since the TUM graduates were able to help different researchers with their questions. They investigated for instance how the body temperature acts at minus 10 degrees in a cooling chamber. Here they were able to test whether the quality of a cheap parka is worse than that of an expensive one.

The sensor does not just measure the body temperature during functional clothing testing for the protective clothing of astronauts, firemen or race drivers. With this device you can also measure the vital signs of athletes. “The sensor which measures pulse repetition frequency and body temperature at the same time will be interesting for athletes, since it could replace conventional chest harnesses. A lot of athletes wear pulse chest straps, which pinch after a very short amount of time. On women they are generally irritating, but there is virtually no alternative. Via the combination of pulse repetition frequency and temperature measurement in the ear, we want to improve this situation, “ says Kreuzer.

Basically, one differentiates between measuring body temperature and pulse repetition frequency. After all, temperature measurement is done through a special temperature sensor that is fitted in the ear canal. In contrast, frequency measurement works optically, the researchers explain. Here light is irradiated into the tissue and then the intensity in which it returns again is being measured. For this reason it is comparable to the principle of pulse oximetry, a non-invasive procedure to determine arterial oxygen saturation.

The monitoring data can be conveyed to an end device in different ways. Located behind the ear is a sensor that collects data. The reading is then sent to a data logger, a small box in your trouser pocket, or directly sent to a cell phone. In addition there is the possibility to send the data to a personal computer.

This way, different areas of application are available for the device in the future. Nevertheless, the scientists in Munich continue to fine tune their new discovery. “We would like to still improve the measurement of pulse repetition frequency in the future. It is also our goal to incorporate pulse oximetry into the device. The area of vital signs is meant to be developed even more,“ Kreuzer reveals.

The interview was conducted by Diana Posth and translated by Elena O'Meara.