A patch with a universal acoustic sensor

The "patch" sensor can monitor the work of the heart and recognize speech

Anastasia Krasnianskaya, Geektimes

Physiological mechanical and acoustic signals can give us a lot of useful information, including about the state of health. The problem is that they cannot be heard without the help of special devices. Ordinary stethoscopes and digital accelerometers are capable of capturing some information, but they are not suitable for using them in continuous, wearable mode. In addition, both have disadvantages related to the mechanical transmission of signals through the skin. Scientists have presented a new device in which all these shortcomings have been eliminated.

A soft acoustic sensor, which can be worn on the skin as a patch, tracks the heart rate and recognizes human speech. This was stated by a team of creators from the University of Illinois at Urbana-Champaign. Such an epidermal sensor can help diagnose diseases and allow people to control robots and play computer games without a pocket device.

A picture from the University of Colorado Boulder press release
Tiny electronic device can monitor heart, recognize speech – VM

Previous developments that detected acoustic vibrations through the skin mainly worked on the principle of a stethoscope. According to the lead author of the study, Howard Yu Hao Liu, they were too large and were created from rigid materials. Such devices were difficult to wear and they muffled acoustic signals to some extent.

Unlike the bulky devices created earlier, the new sensors use miniature low-power MEMS accelerometers. They are placed in a plate of sticky and elastic silicone rubber. The researchers say that these accelerometers are tuned to vibrate frequencies in the range of 0.5 to 550 Hz. This frequency is characteristic of the sounds that are made by the vital organs of the human body. Elastic copper wires connect these sensors to amplifiers, resistors and capacitors.

The new device, similar to a small patch, weighs only 213.6 milligrams. Its thickness is 20 millimeters. The device is quite flexible and elastic, so it can be worn on any part of the body, including the neck. Someone will decide that wearing a rubber plate for any length of time on the body is very uncomfortable. At least because the skin under it will heat up and sweat. But scientists claim that silicone rubber, from which the "patch" is made, ensures the evaporation of sweat. The device also has electrodes that record the body's electrical signals. They help the sensor monitor the work of the heart and pacemakers.

Device diagram: A – the structure of the device; B – an illustration of the assembled device; C – a curved device supported by tweezers; D – a sensor on the skin; E – fluorescent micrographs of cells cultured on the surface of the device. The green and red areas correspond to living and dead cells; F is a demonstration of the stretching capabilities of the device; G is the results of modeling interconnected structures experiencing the greatest stress, H is the sum of vibrational reactions measured on a chicken breast – tissue simulation on a vibration source.

Experiments have shown that the sensor can continuously collect several different types of acoustic signals at once: opening and closing of heart valves, pulsation of blood in the carotid artery in the neck, vibrations of the vocal cords and movements in the gastrointestinal tract. Scientists conducted tests on volunteers at a private medical clinic in Tucson, Arizona. During the tests, it turned out that the device is able to detect heart murmurs. Scientists also conducted an experiment using the ventricular support system of the heart. This device helps the heart to pump blood, thereby partially or completely replacing its function. Scientists simulated the work of the heart in this way, and also modeled the conditions for thrombosis and embolism. The new sensors coped with the task and were able to detect blood clots that could potentially lead to death.

In addition to medicine, scientists have found other uses for their device. If you stick a "patch" to your throat, you can use it to control robots or play video games, serve as an interface for sending commands to a computer. The sensor, placed accordingly, can capture signals from the muscles of the articular apparatus and acoustic vibrations of the vocal cords. The volunteer could control the Pac-Man character by giving voice commands "up", "down", "left" and "right". The accuracy of word recognition was 90%.

Speech recognition: A – location of the device on the body of the participant of the experiment; B – measurement of articular muscle signals (top) and acoustic signals (top); C – comparison of words in a quiet (left) and noisy (right) environment recorded from the device (top) and an external microphone (bottom); D – matrix, describing the accuracy of speech recognition; E – speech recognition in the game

The close contact between the sensors and the skin makes their operation practically independent of the surrounding acoustic noise. In the diagram, you can see a comparison of the spectrograms of word commands recorded during the game by an epidermal sensor and a standard iPhone microphone that were attached to the throat. The noise sources were located 2.5 meters from the object. In a calm environment, where the noise level did not exceed 30 dB, the sensor and microphone showed similar results. In a noisy environment (60 dB), the recording of the microphone was significantly affected, but this did not affect the work of the prototype in any way.

So, the device can be used for communication in conditions of increased noise. Howard Yu Hao Liu believes that the sensor can also help people with speech disorders, soldiers on the battlefield and first-hand witnesses in disaster areas.

Now the work of the prototype depends on the wires through which the data is transmitted. To make it more practical for use in the real world, a team of scientists is going to completely switch the device to wireless data transmission. In the future, subsequent studies will help to increase the frequency range of vibrations recognized by the epidermal sensor to 2000 Hz. Then the prototype will recognize the full range of vibrations of human speech and will be able to act as a microphone.

The scientific work of Liu et al. Epidermal mechano-acoustic sensing electronics for cardiovascular diagnostics and human-machine interfaces was published in the journal ScienceAdvances on November 16, 2016

Portal "Eternal youth" http://vechnayamolodost.ru  21.11.2016