Highly Sensitive Sensors to Measure the Heart and Brain Activity

Marleen Schweichel and Stefan Schröder have actually established a sensing unit idea for radio frequencies, which is self-powered.
© Julia Siekmann, CAU

Electrical signals measurements such as the ECG (electrocardiogram) can demonstrate how the human brain or heart works. Next to electrical signals magnetic signals likewise expose something about the activity of these organs. They might be determined with little effort and without skin contact. However the particularly weak signals need highly sensitive sensors. Researchers from the Collective proving ground 1261 “Magnetoelectric Sensors” at Kiel University have actually now established a brand-new idea for cantilever sensors, with the future objective of determining these radio frequencies of heart and brain activity. The incredibly little, energy-efficient sensors are especially appropriate for medical applications or mobile microelectronics. This is enabled by the usage of electrets. Such product is completely electrically charged, and is likewise utilized in microphones for hearing help or smart phones. The research study group provided its sensing unit idea in a scandal sheet of the distinguished journal Nano Energy.

Illustration of the sensor set-up By using an electromagnetic field, the flexing beam vibrates. A completely electrically charged electret (blue) pulls the flexing beam. In this manner his vibrance gets more powerful and likewise the discharged electrical signal. © Marleen Schweichel

A lot more efficient: transforming power into electrical energy

The research study group led by Teacher Rainer Adelung, working group “functional nanomaterials”, and Teacher Franz Faupel, working group of multicomponent products, concentrates on cantilever sensors. These include a thin silicon strip, which in the easiest case has 2 layers used: the initially reacts to electromagnetic fields (magnetostrictive product), and the second can give off an electrical voltage (piezoelectric product). “If a magnetic field occurs, the first  layer deforms and thus bends the whole strip – which vibrates like a diving board at a swimming pool,” discussed CRC member Faupel the fundamental concept. Due to the contortion, the 2nd layer releases a quantifiable voltage signal.

“With our new sensor concept, we searched for a way to make this conversion of mechanical energy into electrical energy even more effective, by giving the bending beam more impetus,” discussed doctoral scientist Marleen Schweichel. The more the flexing beam vibrates, the more powerful the discharged electrical signal.

Tough product made to vibrate

Usually, so-called soft products such as plastics vibrate at a radio frequency. The vibration is hence substantially damped, and the discharged signal is extremely weak. With difficult products, considerable damping can be prevented. Nevertheless, a bigger mass of product is needed for this function, which can barely suit the little measurements of the sensing unit technology. “With our approach, we were able to make a small bending beam made of hard material behave like a soft material, and vibrate at low frequencies – and what’s more, at an even greater amplitude,” summed up Adelung what is so unique about their findings.

Electret products: completely electrically charged

The definitive aspect was the so-called electret. The research study group used this completely electrically charged product beneath the flexing beam. Usually, the vibrating flexing beam presses back into its initial position. Nevertheless, due to its self-equilibrating tension, the electret pulls the flexing beam in the opposite instructions, and thus amplifies the vibration of the beam – and hence the electrical signal of the sensing unit.

In order to be able to read this signal as precisely as possible, the research study group likewise incorporated a brand-new method towards sound decrease into its alternative sensing unit idea. With a very quick measurement, the private signals can be “picked up” in between the sound, according to very first author Mona Mintken from the working group “functional nanomaterials”.   

Sensing unit with integrated power supply

Thanks to the electrets utilized in the sensors, it’s not just radio frequencies which can be determined much better. Comparable to irreversible magnets, which produce their own relentless electromagnetic field without a power supply, electrets likewise produce their own irreversible electrical field. “The electret thereby gives the sensor a built-in electrical potential. The sensor itself then requires no external power supply, and can be used for mobile applications,” discussed doctoral scientist Stefan Schröder. Through a cooperation contract, he invested 3 months looking into at the Massachusetts Institute of Technology (MIT) in the United States, in order to more enhance the needed unique electret layers. To do so, he utilized the so-called iCVD (initiator chemical vapour deposition) procedure, which makes it possible for private product layers to be transferred with high accuracy.

“The electrets work like a kind of nano-generator, which generates electrical energy. And can do this theoretically for over twenty years,” stated products researcher Faupel. “Sensors with an integrated power supply in such small sizes are also exciting for applications in the area of the ‘Internet of Things’, which connects decentralised, autonomous electronic systems,” included Adelung.

About the pri­or­ity re­search area KiN­SIS

Details, which are only a millionth of a millimetre in size: this is what the top priority research study location “Kiel Nano, Surface and Interface Science – KiNSIS” at Kiel University has been working on. In the nano-cosmos, different laws prevail than in the macroscopic world – those of quantum physics. Through intensive, interdisciplinary cooperation between physics, chemistry, engineering and life sciences, the top priority research study location objectives to comprehend the systems in this measurement and to carry out the findings in an application-oriented way. Molecular devices, ingenious sensors, bionic products, quantum computer systems, advanced treatments and far more might be the result. More info at www.kinsis.uni-kiel.de

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