Biosensors

2023: Discovered nanoparticle effect will enable biological sensors

An international team of physicists has shown that a certain shape allows nanoparticles to be in an electromagnetic sense larger than their geometric dimensions. This was announced on August 14, 2023 by representatives of the Moscow Institute of Physics and Technology. The discovered effect will help in the creation of biological sensors, materials for solar panels and elements of optical and quantum computers. Read more here.

2020

Start using biodegradable implants to measure nitrogen oxides

In mid-November 2020, researchers at the University of Pennsylvania developed an implantable sensor that can measure the levels of NO and NO2 gases in the body. The flexible sensor, which consists of silicone and magnesium, is completely biodegradable, so it does not need to be removed after implantation. Read more here.

Electronic sensors of temperature, oxygen in the blood and ECG began to be applied directly to the skin

In mid-October 2020, researchers from Pennsylvania State University and Harbin Institute of Technology in China developed a way to print electronic sensors directly on the skin without releasing excessive heat in the process. Thanks to this technique, doctors can receive high-quality recording of a number of vital signs, for example, temperature, blood oxygen content and ECG.

Biometric sensors usually work best when placed in close proximity to the body. While wearable devices such as wrist pulse oximeters are already commonplace these days, they can only be worn over some areas of the body and are often not too comfortable. Therefore, the researchers developed a new technique.

Electronic sensors of temperature, oxygen in the blood and ECG began to be applied directly to the skin

Bonding silver nanoparticles into flexible electronic components typically requires high temperature sintering at 300 degrees Celsius, which cannot be performed directly on the skin. The team of researchers decided to find a material that would lower the temperature required for sintering and developed a sintering paste layer of polyvinyl alcohol and calcium carbonate. This paste not only provides sintering of the nanoparticles at room temperature, but also makes the surface of the resulting material smooth and flexible, which allows the sensors to be applied directly to the body.

Researchers have already created sensors to assess blood oxygen, take ECGs, measure temperature and humidity. They also connected the sensors to a common network that can transmit real-time readings to a nearby monitor. The sensors can work for several days, and they can be removed easily under a hot shower. In this case, all devices can be reused or sent for recycling, since they are not damaged during the removal process.^[1]

MIPT found a way to raise the sensitivity of biosensors to a level sufficient for domestic use

On January 28, 2020, the MIPT reported that a way was found to raise the sensitivity of biological sensors to a level sufficient for their use in household appliances. The work was carried out by MIPT with the support of the Russian Science Foundation.

Biosensor is an electrochemical sensor that allows you to determine the composition of biological fluids in real time. The MIPT noted that the only mass household use of biosensors is devices for instant measurement of blood glucose levels. But futurologists promise that in the near future, household electronic devices that analyze the composition of sweat, saliva, eye fluid and other secretions using biosensors will be able to identify the person, make medical tests, make diagnoses, continuously monitor the state of health and make the optimal diet for a particular person depending on the current state of his body.

Until recently, their low sensitivity and unbearable cost for the consumer market did not allow them to seriously talk about such applications of biosensors. But it seems that a breakthrough is planned in this area: a group of scientists from Fiztech proposed a fundamentally different biosensor design, promising to increase its sensitivity and reduce cost. Both are many times over.

"A traditional biosensor consists of an annular resonator and a waveguide located in the same plane as the resonator. We decided to try to separate these two elements, place them in different planes, arrange the ring above the waveguide, " noted Kirill Voronin, author of the idea, master's student at MIPT and employee of the laboratory of nanoptics and plasmonic

Previously, none of the researchers tried to do this, because in laboratory conditions it is much easier to make a single-level flat structure: a thin film is applied to the substrate, etched out it and both the ring resonator and the waveguide are obtained at the same time. The two-tier design of the biosensor turned out to be more difficult to manufacture in single experimental copies, but cheaper in mass production at microelectronics plants, where all technological processes are focused on the layered placement of active elements.

But the main thing is that the proposed volumetric design of the biosensor makes it possible to achieve many times more sensitivity from it, according to the MIPT.

The work of biosensors is based on the fact that due to the absorption of organic molecules by the surface of the sensor, a slight change in the refractive index of the latter occurs. This change is captured by a resonator whose resonance conditions depend on the refractive index of the external medium. The resonance phenomenon has the property that even the weakest fluctuations in refractive index cause a significant displacement of the resonant peaks. Therefore, the biosensor is able to respond to almost every organic molecule that falls on the surface of the sensor.

"We have a strip waveguide located under the resonator, in the thickness of the dielectric. The resonator is located at the interface between the dielectric substrate and the external environment. This makes it possible to significantly increase its sensitivity by selecting the refractive indices of two media, " noted Alexey Arsenin, one of the co-authors of the work, leading researcher at the Laboratory of Nanoptics and Plasmonics MIPT

In the biosensor layout proposed by scientists, its entire optical part - the source and detector of radiation - is located inside the dielectric. Outside, only the sensitive zone of the structure remains - a golden ring with a diameter of several tens of micrometers and a thickness of several tens of nanometers.

Biosensor device. The waveguide is located inside the dielectric. The resonator in the form of an annular waveguide is located outside the substrate, on the border with the studied biological fluid. Changing its refractive index results in a resonance curve offset. Sensors

"Our scheme is designed to significantly simplify and reduce the cost of biosensors. For the production of sensors built on our principle, only optical lithography is enough. No moving parts are required, enough customizable laser working in a very narrow range, " noted Kirill Voronin, author of the idea, master's student at MIPT and employee of the laboratory of nanoptics and plasmonic

According to Valentin Volkova, director of the Center for Photonics and Two-Dimensional Materials at MIPT, it will take about three years to create an industrial model based on the proposed technology.

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