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Tag: Saint Petersburg Electrotechnical University “LETI”

Researchers create a multifunctional biochip to diagnose chronic diseases

Posted on by Saint Petersburg Electrotechnical University

Today, the most important problem of biomedical analysis is the prompt diagnosis of chronic diseases – in particular, cardiovascular diseases, which are the main cause of mortality, according to the WHO. Timely diagnosis and care are often decisive factors determining the disease’s progression. The main preclinical diagnostic tool is electrocardiography, which, however, often fails to identify the developing myocardial infarction.

“Today, there is a growing prevalence of chronic and systemic diseases in the population, such as cardiovascular diseases – heart attack, stroke, chronic heart failure, rheumatoid arthritis, systemic sclerosis, pancreatitis, and others. At the time when HIV/AIDS, tuberculosis, and malaria are spreading, these problems seem less important, but WHO statistics show that it is chronic diseases that lead to reduced life expectancy, disability, etc. Therefore, cheap, timely, and accurate diagnosis of chronic diseases is crucial for successful treatment and prevention of their development,” says Tatiana Zimina, Associate Professor of Department of Micro- and Nanoelectronics of ETU “LETI”.

According to scientists, it is more reliable to confirm the diagnosis using biochemical methods, namely the analysis of disease biomarkers in the blood. LETI scientists suggested using new approaches when creating tests: identification of protein markers (proteomics), bioinformatics, and others.

“Currently, a large number of protein biomarkers of diseases have been identified. Based on this, we can build a system that allows prompt decision-making for each patient. However, the existing means of a biochemical diagnosis of chronic diseases are expensive and labor-intensive, and some of them have unsatisfactory accuracy,” explains researcher.

The LETI research team aims to find ways to create a cheap and versatile biochip-based system for a rapid diagnosis of chronic diseases. The work is conducted jointly with the Almazov National Medical Research Centre. The team includes specialists in biophysics, information technology, micro- and nanoelectronics, biochemistry, nanotechnology, precision mechanics, and other areas.

“There are three complementary areas in the project: modeling the spatial structures of proteins using bioinformatics, verification of modeling results with experimental results of analysis of biochemical properties of proteins, and development of lab-on-a-chip for rapid disease diagnostics,” says Oleg Markelov, Head of the “Advanced Wireless Technologies” area at ETU “LETI.”

At the first stage, LETI scientists will assemble a library of protein markers characterizing a particular disease. In the second stage, they will develop a compact hybrid-integrated circuit board (biochip). Scientists will teach it to recognize various disease protein markers with high accuracy and selectively capture them. In addition, the project will develop a methodology for diagnosing chronic diseases using biochips. LETI researchers have already begun systematizing known biomarkers related to human physiological parameters.

LETI scientists and their colleagues from the Almazov Center plan to develop a biochip-based system by 2024. A patient will have to submit blood or saliva samples for analysis. The test result will be ready within half an hour, which is tens of times faster than traditional blood tests. After receiving the patient’s express results, the doctor will be able to decide if more thorough quantitative tests are necessary.

How material for high-speed switchable devices transitions into conducting state

Posted on by Saint Petersburg Electrotechnical University

A team of physicists from Saint Petersburg Electrotechnical University “LETI” studied and described the main factors that affect the transition of vanadium dioxide (VO2) thin films into the conducting state. The team identified two different transition mechanisms that depend on the number of defects in a sample: the fewer defects, the less voltage is required for transition, and the more independent voltage threshold is from temperature. The results of the study were published in the Chaos, Solitons & Fractals journal.

In their normal state, vanadium dioxide (VO2) films cannot conduct electricity. However, when subject to a certain voltage level, their resistance reduces by up to a hundred thousand times. Such a transition can happen very fast — in less than a picosecond. The mechanism of this process is still largely unknown, but this unique property makes vanadium dioxide films a promising material for smart windows, thermal imagery sensors, and artificial neurons for next-generation computers.

“One potential area of application of VO2 thin films is active memristors. Thanks to resistive switching in active memristors, they can be used to simulate the behavior of voltage-gated ion channels in biological neurons, and phase transition in VO2 thin films makes it possible to model different types of spike activity of neurons. Potentially, the modeling results could help scientists study the time synchronization of the neurons that support the functional activity of the brain and find ways for their synchronization or modulation. Based on these studies, non-pharmacological correction methods for certain functional brain states could be developed,” says Natalia Andreeva, a lead researcher at the Nanotechnologies Science and Educational Center of ETU “LETI.”

In its work, the team from ETU LETI studied the switching dynamics in a broad temperature range: from -200 to +20°С. To do so, they made several identical samples by covering a sapphire base with a thin layer of vanadium dioxide using the method of reactive magnetron sputtering. During this process, particles are dislodged from a bar of the sputtered material by gas ions in a strong magnetic field. Then, different voltage levels were applied to the samples at different temperatures, and the team studied the current flows through VO2 thin films.

Based on the experiment results, the team divided all VO2 thin film samples into two types. The first one required more voltage to transition to the conducting state when the temperatures went down, and the second one did not exhibit any threshold voltage changes correlating with temperature. According to the team, the difference might be due to the number of defects, namely, ions of hydrogen and oxygen vacancies (i.e. areas lacking atoms of oxygen).

In some cases, the defects could act as electron traps, and for the transition to the conducting state to happen, all of them should be filled. This requires a certain threshold voltage. When a sample has a relatively small number of defects, the threshold voltage is low and does not depend on the temperature; the transition to the low resistance state in VO2 thin films is preferably electronically driven. On the contrary, at increasing the number of defects in a sample, the higher voltage bias is required for the transition to the low resistance state, and more likely that it is triggered due to thermal heating. In this case, the threshold voltage is temperature-dependent. When a sample is cooled down and subject to a voltage at the same time, more voltage is required for the transition with the temperature decreasing.

“We are going to continue working on this task in the framework of the state project “Bionic neuroarchitectonics.” Namely, we plan to model neuroprocessing activity using cutting-edge smart materials and technologies,” concluded Natalia Andreeva.

LETI scientists create a model describing internal processes in the artificial muscles of microbots

Posted on by Saint Petersburg Electrotechnical University

A team of scientists from Saint Petersburg Electrotechnical University “LETI” developed a computer model to study the internal processes in the electrical components of microbots and to predict their reactions to different conditions. The work was supported by a grant from the Russian Science Foundation, and an article about it was published in the Micromachines journal.

To work with nano- and microsized details or in hard-to-reach places, modern-day scientists use microbots. For example, in medicine, they are used for target drug delivery or non-invasive surgeries.

“Most polymers are flexible, lightweight, and easy to manufacture and process. In addition to these properties, an ionic polymer-metallic composite material (IPMC) is also able to actively deform in response to several volts of voltage applied to electrodes. Because of that, it can be used as a material for soft robotized drives, artificial muscles, and dynamic sensors for bionic engineering,” said Ivan Khmelnitskiy, Assistant Professor at the Department of Micro- and Nanoelectronics of LETI.

An ionic polymer-metallic actuator (activation device) is a mechanism that consists of a polymer membrane covered with a conductive layer of metal on both sides and electrodes with 1V to 5V voltage attached to it. Before use, the polymer is saturated with water. The liquid starts moving under the influence of the electric field, increasing the pressure on one electrode and reducing it on the other. This pressure difference causes IPMC to curve.

Composite materials of this kind can be used to manufacture various microbots. Therefore, it is extremely important to understand the processes that happen inside them under the influence of applied voltage to accurately predict the reaction of the membrane. To do so, scientists use complex mathematical models that calculate the internal processes based on the initial observational data. However, most mathematical models require a lot of computational resources and are quite expensive. Therefore, scientists are looking for optimization methods that would simplify the research and development of microdevices.

A team of researchers from LETI created a computer model that requires minimal resources to program an algorithm and create a simulator to monitor all necessary processes. The model consists of adjoint differential equations that describe the transportation of charged particles (ions) and water molecules in an ion-exchange membrane, as well as the electrostatic field inside it and the mechanical deformation of the mechanism. To calculate these values, the scientists added geometric characteristics (length, width, layer thickness, etc) and physical properties (diffusion coefficient, ion concentration in the polymer, layer density, etc) to the model.

“Using the novel computational modeling software, we calculated and studied the spatial distribution of ions and water molecules in an IPMC polymer membrane. The optimized model suggested by our team provides for the monitoring of ion transportation dynamics in the composite material depending on membrane parameters and control voltage,” says Eugeny Ryndin, Professor of the Department of Micro- and Nanoelectronics of LETI

“Our work supports calculations with complex modern-day mathematical models and provides for international-level results, but requires quite simple equipment: a personal computer with free software. We hope that the simulation methodology described by our team would spur further developments in this field,” commented Anton Broyko, Assistant Professor at the Department of Micro- and Nanoelectronics of LETI.