28 November 2017

Radio shirts have learned to count the pulse

"The Attic" Researchers from Cornell University have developed a method that allows you to track the movement of the chest using radio frequency signals.

Moreover, the antennas that allow you to collect data on the state of organs have learned to sew directly into pockets.

Accurate measurement of the main vital signs: heart rate and pulse, blood pressure and respiratory rate is important for monitoring the patient's health. However, modern devices for assessing vital signs are quite bulky and require direct contact with the skin, so they are not very convenient to use.

This problem was elegantly solved by two researchers who developed a method based on the technique of coherent near-field sensing, that is, on reading information from a distance of less than 20 cm from the surface. The scientists decided to use radio frequency object identification (RFID) tags sewn into the fabric of the shirt, which by definition is located close to the skin.

A radio frequency object identification tag is a miniature storage device. It consists of a microchip that generates a radio signal and an antenna that receives the signal and transmits it to a reader receiver. Reading codes in stores is based on this principle – for example, this is how the American retail chain Wal-Mart works.

Since the phase of the electromagnetic signal is very sensitive to the distance between the receiver (scientists used a mobile phone as a receiver) and the label sewn into the shirt – the source of the radio signal, phase fluctuations carry enough information and are quite suitable for assessing the movement of the human chest.

However, the radio frequency tags that scientists used for their radio shirts are still different from the tags that stores use to account for goods. The label "modified" by the inventors allows you to separate the weak pulse beat from the powerful movement of the chest. As a result, strong signals do not overlap weak ones and data from different organs can be analyzed separately.

The researchers expect that the radio shirt will make it easy and without unnecessary discomfort for patients to monitor the health of the elderly. What is especially important, the reader can simultaneously process several signals from different patients, which will save the doctor's time and reduce the cost of tests.

At the bottom is a prototype of the sensor, at the top is its real embodiment (VM).

Article by Xiaonan Hui & Edwin C. Kan Monitoring vital signs over multiplexed radio by near-field coherent sensing is published in the journal Nature Electronics.

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