Biosensors integrated into smartphones, smart watches, and other gadgets are about to become a reality. In a paper featured on the cover of the January issue of Sensors, researchers from the Moscow Institute of Physics and Technology describe a way to increase the sensitivity of biological detectors to the point where they can be used in mobile and wearable devices. The study was supported by the Russian Science Foundation.
A biosensor is an electrochemical device that determines the composition of biological fluids in real- time. Blood glucose meters used by diabetic patients may well be the only mass-market biosensing devices in use today.
Biosensor layout (a, c). The waveguide is inside the dielectric substrate. The resonator, realized as a ring waveguide, is positioned at the interface between the dielectric material and the biological fluid that is analyzed. A change in the fluid's refractive index shifts the resonant curve (b).
Credit: Kirill Voronin et al./Sensors
But futurologists say household appliances will soon be able to analyze sweat, saliva, aqueous humor, and other bodily fluids to identify a person, make medical tests, diagnose disease, or continuously monitor the health of an individual and make optimal diet suggestions accordingly.
Until recently, such applications were not seriously considered, because the available devices were not sensitive enough and were prohibitively expensive for the consumer market. However, it may be that a breakthrough is about to happen.
A team of researchers from the MIPT Center for Photonics and 2D Materials has proposed a radically new biosensor design, which could increase detector sensitivity many times over and offer a similarly impressive reduction in price.
"A conventional biosensor incorporates a ring resonator and a waveguide positioned in the same plane," explained MIPT graduate student Kirill Voronin from the Laboratory of Nanooptics and Plasmonics, who came up with the idea used in the study. "We decided to separate the two elements and put them in two different planes, with the ring above the waveguide."
The reason researchers did not test that sensor layout before is that manufacturing a flat, single-level device is easier in a laboratory setting. By depositing a thin film and etching it, both a ring resonator and a waveguide are produced at the same time.
The alternative two-level design is less convenient for manufacturing unique experimental devices, but it turned out cheaper for mass-producing sensors. The reason for this is that the technological processes at an electronics plant are geared toward layer-by-layer active component placement.
More importantly, the new two-tier biosensor design resulted in a many times higher sensitivity.
A biosensor operates by registering the slight changes in the refractive index at its surface, which are caused by organic molecule adsorption. These variations are detected via a resonator whose resonance conditions depend on the refractive index of the external medium.
Since even the slightest fluctuations in the refractive index cause a significant resonant peak shift, a biosensor responds to nearly every molecule that lands on its surface.
"We have positioned the strip waveguide under the resonator, in the bulk dielectric," said paper co-author Aleksey Arsenin, a leading researcher at the MIPT Laboratory of Nanooptics and Plasmonics. "The resonator, in turn, is at the interface between the dielectric substrate and the external environment. By optimizing the refractive indices of the two surrounding media, we achieve a significantly higher sensitivity."
The newly proposed biosensor layout has both the source and the detector of light within the dielectric. The only part that remains on the outside is the sensitive element. That is, the gold ring several dozen micrometers in diameter and one-thousandth that in thickness (fig. 1).
According to Voronin, the team's method for making biosensors more responsive will take the technology to a qualitatively new level. "The new layout is intended to make biosensors much easier to manufacture, and therefore cheaper," the physicist said. "Optical lithography is the only technique necessary to produce detectors based on our principle. No moving parts are involved, and a tunable laser operating in a tight frequency range will suffice."
Valentyn Volkov, who heads the MIPT Center for Photonics and 2D Materials, estimates that it will take about three years to develop an industrial design based on the proposed technology.
Ilyana Zolotareva | EurekAlert!
TU Dresden chemists develop noble metal aerogels for electrochemical hydrogen production and other applications
06.04.2020 | Technische Universität Dresden
First SARS-CoV-2 genomes in Austria openly available
03.04.2020 | CeMM Forschungszentrum für Molekulare Medizin der Österreichischen Akademie der Wissenschaften
Electrolytes play a key role in many areas: They are crucial for the storage of energy in our body as well as in batteries. In order to release energy, ions - charged atoms - must move in a liquid such as water. Until now the precise mechanism by which they move through the atoms and molecules of the electrolyte has, however, remained largely unknown. Scientists at the Max Planck Institute for Polymer Research have now shown that the electrical resistance of an electrolyte, which is determined by the motion of ions, can be traced back to microscopic vibrations of these dissolved ions.
In chemistry, common table salt is also known as sodium chloride. If this salt is dissolved in water, sodium and chloride atoms dissolve as positively or...
Drops of water falling on or sliding over surfaces may leave behind traces of electrical charge, causing the drops to charge themselves. Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz have now begun a detailed investigation into this phenomenon that accompanies us in every-day life. They developed a method to quantify the charge generation and additionally created a theoretical model to aid understanding. According to the scientists, the observed effect could be a source of generated power and an important building block for understanding frictional electricity.
Water drops sliding over non-conducting surfaces can be found everywhere in our lives: From the dripping of a coffee machine, to a rinse in the shower, to an...
90 million-year-old forest soil provides unexpected evidence for exceptionally warm climate near the South Pole in the Cretaceous
An international team of researchers led by geoscientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have now...
The bacteria that cause tuberculosis need iron to survive. Researchers at the University of Zurich have now solved the first detailed structure of the transport protein responsible for the iron supply. When the iron transport into the bacteria is inhibited, the pathogen can no longer grow. This opens novel ways to develop targeted tuberculosis drugs.
One of the most devastating pathogens that lives inside human cells is Mycobacterium tuberculosis, the bacillus that causes tuberculosis. According to the...
An international team with the participation of Prof. Dr. Michael Kues from the Cluster of Excellence PhoenixD at Leibniz University Hannover has developed a new method for generating quantum-entangled photons in a spectral range of light that was previously inaccessible. The discovery can make the encryption of satellite-based communications much more secure in the future.
A 15-member research team from the UK, Germany and Japan has developed a new method for generating and detecting quantum-entangled photons at a wavelength of...
06.04.2020 | Event News
02.04.2020 | Event News
26.03.2020 | Event News
06.04.2020 | Life Sciences
06.04.2020 | Power and Electrical Engineering
06.04.2020 | Social Sciences