FPI SB RAS: Electronic flexible glucose sensors

Main article: Blood glucose monitoring systems

2024: Presentation of laboratory sample of sensor operating at low recording speed

Researchers from the Rzhanov Institute of Semiconductor Physics SB RAS (IFP SB RAS) create electronic flexible glucose sensors that do not require skin puncture. On July 10, 2024, the IFP SB RAS presented a laboratory sample operating at a low recording speed (signal accumulation time 10-30 minutes). As representatives of the institute told the medical portal Zdrav.Expert, the device detects the level of glucose in sweat and will be useful for patients with diabetes mellitus, as well as for those who need to control the level of glucose in the body - for example, athletes or people following a specialized diet.

source = IFP SB RAS

The sensor sensor element (with an area of ​ ​ several square millimeters) is printed on ordinary office paper. But the ink is unusual - the author's development of scientists from the IFP SB RAS. As a result, layers with a thickness of one nanometer, made of graphene and a conductive polymer PEDOT: PSS, are laid on the paper. When such a composite is applied to paper, vertically arranged graphene particles are formed in the layer, which act as catalysts for the oxidation of glucose, and the level of the sensor signal (its conductivity) depends on the amount of oxidation products. According to researchers at the IFP SB RAS, this is the first sample of this type of sensor in Russia.

source = IFP SB RAS

The sensor can be placed on the wrist or almost anywhere where the user is comfortable. A small module is also being developed for the sensor for fast reading (in a split second), converting, amplifying the signal and transmitting data to the phone via a Bluetooth channel.

Detailed results of the work of scientists are published in the journals Physical Chemistry Chemical Physics, Russian nanotechnology (accepted for publication), Successes in physical sciences. In addition, a patent of the Russian Federation No. 2811305 was obtained for the invention.

"Non-invasive (skin-puncture-free) glucose sensors are being developed worldwide. As a sensing element, a generally multilayer structure, a rather thick 'patty', is created. In this case, in order to ensure a high signal level, abundant sweating is required and additional heating of the skin is required. We chose a different path - we made a very thin layer with a certain structure that provides selectivity, and got a high sensor sensitivity. But it was necessary to solve multivariable problems, ranging from the development of the composition of ink, the ratio of components, their viscosity, concentration and ending with the selection of the printing mode and the basis for ink application, "said Irina Veniaminovna, head of the scientific group, leading researcher at the Laboratory of Physics and Technology of Three-Dimensional Nanostructures of the IFP SB RAS.

source = IFP SB RAS

As optimal materials for printing a flexible sensory layer, scientists chose office paper and a nonwoven fabric (spanlace). But many fabrics were tested - from silk to cotton, polymer materials, different types of paper.

According to IFP SB RAS, the sensor created by scientists is of the resistive type: its electrical resistance changes when glucose molecules hit the sensitive element. As a result of interaction with later, the conductivity of the sensor increases, which can be fixed by supplying voltage and measuring electric current. The conductivity of the sensor is shown to be proportional to the blood glucose content. In this case, sensitivity is important, the absolute magnitude of the signal and the speed of its appearance after the start of testing depends on it and, most importantly, the range of changes in the signal: the larger it is, the smaller glucose fluctuations can be measured.

"The difference between our sensor and those developed by other groups in Russia and abroad is that we have found an easy and cheap way to get a high response using graphene as the main sensitive matrix. Other authors chose other components as a sensor, while graphene only amplified the signal. At the very beginning, it seemed to us that an increase in the thickness of the printed layer (within reasonable limits - up to 10 nanometers) would lead to an increase in the signal, and more reproducible results would be obtained. We tried to make thicker layers, but it was very difficult to achieve a significant change in their conductivity, even when the sensor was wet. The thick layers produced a good signal and a fast response, but the change in signal as the sugar changed was relatively low, about 30%. In the world, many sensors have just such a response. But we wanted more, and we came to an optimal ratio of the composition of the layer, its thickness and structure. It turned out that the best characteristics are given by two to three printed layers. In this case, the graphene coating should be continuous. To do it this way, I had to choose about ten different parameters, "explained Artyom Ilyich Ivanov, a researcher at the youth laboratory of nanotechnology and nanomaterials, candidate of physical and mathematical sciences.

Artyom's tasks included creating ink, searching for components for them, determining the ratios of the latter, selecting printing modes, choosing the substrates on which printing was carried out. All of these processes play a crucial role in creating a sensor.

A scientific group of five people participates in the development of the device, including students of the Novosibirsk State Technical University (NSTU NETI), for whom the research results form the basis of qualification work.

source = IFP SB RAS

For example, Anna Andreevna Buzmakova, a master's student at the Faculty of Radio Engineering and Electronics (REF) of NSTU, studied the dependence of electrical resistance on the composition of the composite material as part of her bachelor's diploma, changing the size of graphene particles and the concentration of polymer.

Ruslan Sayatovich Kumarbayev, 2nd year master's student at the EF NSTU, is responsible for designing and assembling the module for reading, converting and transmitting the sensor signal to a smartphone. In addition, Ruslan has created and is working on a mobile application that is responsible for processing data received from the sensor. The student demonstrates a creative approach to selecting the parameters of the circuits and the reader. He is looking for ways to make the reading module flexible and miniature.

source = IFP SB RAS

The researchers emphasize that the presented device is not a medical device, it is a sensor for domestic use. Specialists have to work out the reading parameters so that each user can correlate the sensor signal values ​ ​ with those already known to him - for example, glucometer indicators or medical test results.

"Our plan for the maximum for the next few years is to make the device work easily and reliably, and the results obtained are understandable to any person, without special immersion in the topic. The advantage of our sensors, in addition to sensitivity - cheapness, maintaining performance when storing the sensor for more than two years, the ability to reuse - on one sensor we made about 30 measurements. And when it was necessary to clarify the results, they took another dozen measurements on the same structure and saw good reproducibility of the results. Sensors are interchangeable and in case of violation of one, the following is used, "added Irina Antonova.

She emphasizes that despite the obvious promise of development (more and more people need constant glucose monitoring), there are not many support measures that fund research. As of July 2024, work is being carried out within the framework of the project of the Russian Science Foundation No. 22-19-00191, but is not the main task of the project.

"While we are still far from the stage of creating a commercial product. Scientific, search research requires both time and cost. And most of the support programs that we were able to find offer to finance the refinement of an almost complete product or prototype, "explains the head of the scientific group.

Scientists are still gaining statistics on the change in the sensor signal depending on the individual characteristics of the person. For example, by rapidly reading a signal (milliseconds), it is possible to determine the time between a meal, an increase in blood glucose (determined by a glucometer) and a change in glucose in sweat. The response of the sensor to small physical activities is also investigated. The research is executed with financial support of the Ministry of Education and Science of the Russian Federation.