A new method of creating composites will reduce the hypersensitive sensors for medicine

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MISIS University of Science and Technology 24 March 2023 14:35

NUST MISIS scientists have proposed a new method for creating a miniature magnetoelectric composite that will reduce hypersensitive sensors for medical applications. The results of the work are published in the scientific journal Materials.

For non—invasive methods of diagnosing diseases - magnetoencephalography (study of magnetic fields of the central nervous system) and magnetocardiography (study of magnetic fields in the heart muscle), which allow studying various diseases at early stages (multiple sclerosis, Alzheimer's disease, schizophrenia, neuralgia, etc.), arrays of hypersensitive and at the same time miniature sensors on the based on superconductors. However, such sensors require expensive cooling systems, which affects their overall cost.

It is possible to significantly reduce the price of sensors if composite magnetoelectric materials (ME composites) consisting of magnetostrictive and piezoelectric layers connected to each other are used as their sensitive elements. However, such elements are poorly amenable to miniaturization, since in order to obtain the greatest sensitivity to the magnetic field, the ME material must be "magnetized", that is, placed in an external magnetic field, which is applied, for example, with the help of an additional electromagnetic coil.

The need for an additional magnetic system does not allow us to use only microelectromechanical system technologies (MEMS technologies), well-developed for silicon electronics, to create sensors. This forces researchers around the world to look for other approaches to the magnetization of ME composites.

A group of MISIS University scientists led by Andrey Turutin, Senior Researcher at the Laboratory of Physics of Oxide Ferroelectrics, together with colleagues from Mapper LLC — a leading Russian company engaged in MEMS technologies has proposed the construction of a ME composite with a magnetostrictive layer of an amorphous alloy called metglass (Fe70Co8Si12B10) and an additional layer of nickel, which is a source of a magnetizing field.

"Initially, using the microblasting method, we made a console with a thickness of no more than 100 microns from a lithium niobate (NL) crystal. Thus, an ideal mechanical oscillator was practically realized, preserving all the advantages of bulk lithium niobate (NL) crystals. Next, a layer of metglass was applied to the crystal by magnetron sputtering of the target. This type of composite has been well studied by our scientific group and is a model. A separate difficult task was the exact transfer of the composition to the film, since the layer contains four chemical elements," said Ilya Kubasov, co—author of the work, senior researcher at the Laboratory of Physics of Oxide ferroelectrics at NUST MISIS.

The main achievement of the research is that scientists managed to produce a magnetoelectric bending sensor (i.e., an external magnetic field bends the sensing element) of a type with characteristics approaching the maximum possible. At the same time, the sensor developed at NUST MISIS is completely manufactured using microelectronics and MEMS technologies based on a single single—crystal NL substrate - this has become real due to the removal of adhesive layers and mechanical clamps from the structure, which are used in well-known analogues.

"After we worked out the technology for producing MEMS composites, measurements of the magnetoelectric effect were carried out in quasi-static and dynamic modes. It was found that the ME coefficient is 492 V / (cm · E) at the bending resonance frequency, and the sensitivity to the alternating magnetic field reached 12 Pt at the resonant frequency of 3065 Hz. This is at least 5 times higher than the best values known from the literature for magnetoelectric MEMS composites," explained Andrey Turutin, head of the RNF project.

The method proposed by the team will in the near future significantly reduce the hypersensitive magnetic field sensors used, for example, for non-invasive methods of diagnosing diseases. In the future, scientists plan to add magnetizing layers to the developed composites and create arrays of miniature sensors for mapping ultra-weak alternating magnetic fields for the diagnosis of diseases.

The work was carried out with the support of the Russian Science Foundation No. 22-19-00808.

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