Архив рубрики ‘ Nanowire device

Carbon nanotubes pave the way for human breath analysis of lung disease


Point-of-care health monitoring is still a challenging technology under development. Various sensors can be integrated into wearable devices for the monitoring of different health parameters like temperature and pulse rate. However to provide deep health analyses and a prediction for the existence of disease still requires the use of complicated diagnostic tools like MRI, computer tomography, etc, or body liquids analysis from blood, saliva, etc.

Breath is one of the main sources of human health parameters that can be used for predicting the state of different internal organs. Exhaled breath composition is very complex and the existence of disease marker molecules can be as low as 1 ppm (one part per million). That means that using breath for health monitoring purposes requires highly sensitive tools with a recognition ability down to single molecules.

Among a number of methods for breath analysis, the most promising one is based on the concept of an electronic nose. Here, the task for certain disease pattern recognition is moves from hardware to software using advanced methods of data analysis. This concept provides both miniaturizations of sensor designs and fast response times. Yet the development of sensor platforms that provide high sensitivity to the informative molecules with high humidity background in the exhaled breath is still challenging.

A team of researchers from Università Cattolica del Sacro Cuore (Italy), Skolkovo Institute of Science and Technology (Russia) and National Research University of Electronic Technology (Russia), has developed a method for fast, on-site and still accurate breath analysis that does not need special preparation of breath samples. The method is based on an electronic nose platform that uses a set of single-walled carbon nanotube (SWCNTs) sensors deposited on flexible substrates and modified by different semiconducting organic molecules. Carbon nanotubes are widely used for electronic nose development because of their high sensitivity to environmental gases, high stability, and intrinsic variations in electronic properties that make them perfect for use in electronic nose platforms. The researchers suggested improving the recognition properties of the SWCNT sensors by additional functionalization that increases the sensors' specificity to different gases, making sub-ppm analysis possible.

The researchers demonstrated the performance of this method by analyzing Various gases and vapors (ammonia, ethanol, acetone, 2-propanol, sodium hypochlorite, benzene, hydrogen sulfide, and nitrogen dioxide). The sensitivity was demonstrated down to 0.25 ppm for each nanotube sensor area of about 1 cm2 with high level of discrimination between gases. The best detection limit was demonstrated for ammonia for nanotubes covered by PANI molecules and hydrogen sulfide for CNT covered by TCTA molecules of 0.014 and 0.064 ppm, respectively.

Moreover, the team demonstrated that these sensors can be used for chronic obstructive pulmonary disease (COPD) recognition based on breath analyses of 21 individuals. Advanced data analysis methods based on principle component analyses provided a clear distinction between subjects with and without COPD.

The research team, led by Prof. L. Sangaletti, has demonstrated the high performance of their proposed sensing platform in-breath recognition with relatively fast response times without the need for complicated breath treatment. In the case of COPD, they observed that the analysis can be improved by properly targeting the molecules specific to the decease.

The main benefit of such an electronic nose platform is the possibility of future miniaturization and integration on a chip compatible with conventional microelectronics technologies, paving the way for on-site analysis using smartphones.

This project was funded in part by the ANAPNOI project (Catholic University of the Sacred Heart) and the Russian Science Foundation.

Nanowerk May 13, 2020

A Nanowerk exclusive provided by National Research University of Electronic Technology









Nanowire device generates electricity from ambient humidity

Scientists in the US claim to have developed a device that can generate electricity from moisture in the air. The device, based around a thin film of electrically conductive protein nanowires, can produce continuous electrical power for around 20 hr, before self-recharging. The researchers say that such technology could provide clean energy without the restrictions on location and environmental conditions of other renewable energy solutions such as solar cells (Nature 10.1038/s41586-020-2010-9).

The device consists of a roughly 7 µm thin film of protein nanowires, harvested from the microorganism Geobacter sulfurreducens, deposited on a gold electrode with an area of around 25 mm2. A smaller, roughly 1 mm2, electrode is placed on top of the nanowire film.

Jun Yao, an electrical engineer at the University of Massachusetts, and his colleagues found that this set-up was able to produce a continuous current for more than 20 hr. After 20 hr, the voltage had dropped from around 0.5 V to 0.35 V, but when the load was removed, it went back up to 0.5 V within five hours, showing a self-recharging process.

The researchers also connected multiple devices together to increase the output. With 17 devices they were able to generate 10 V, and demonstrated that these connected devices could power an LED or a small liquid crystal display.

G. sulfurreducens was discovered by Derek Lovley, a microbiologist at the University of Massachusetts. He tells Physics World that the bacteria use the electrically conductive nanowires to make connections with other microbial species and with minerals. “For example, in soils and sediments, Geobacter ‘feeds’ electrons to methane-producing microorganisms, which use the electrons to convert carbon dioxide to methane,” Lovley says. “Geobacter also electrically connects to iron minerals in soils and sediments to use iron minerals similarly to how we use oxygen.”

Electricity from thin air

Energy is generated in the device due to a moisture gradient that forms within the nanowire film when it is exposed to the humidity naturally present in air, according to the researchers. The smaller electrode on the top is key, as it leaves one side exposed to the humid air, allowing the moisture gradient to develop.

Yao tells Physics World that the way the device works can be compared with lightning. “The cloud builds up positive and negative charges at the upper and lower sides, and upon a certain threshold, it discharges through the lightening,” he explains. “This indicates that charge can be build up from the ambient environment and we may be able to harvest it for electricity production. One can think of our device to be a small ‘cloud’, with one side open to air and the other sealed. Water molecules in the air constantly bump into the open surface, creating more charges than on the other one. The charge difference eventually will build up electric field or potential difference, which will drive the electric current output.”

The team experimentally determined that ambient humidity was the source of energy by sealing the top of the device, to block water-molecule exchange with the nanowires. This cut the electrical output, which returned once the seal was removed. They also found that increasing the ambient humidity, and thus the water-molecule exchange rate, increased the electric output. To check that there were no electrochemical reactions with the gold plates, the team replaced them with inert carbon electrodes, and were able to generate similar voltages. The device also worked in the dark, eliminating a photovoltaic effect.

Yao says that the researchers are now working on connecting devices together to increase the power volume. “We have demonstrated that the devices can be connected to increase the power, so at a certain point, it is proven this will scale,” he says. “We are working on material sciences and engineering strategies to scale up the technology.”

Physicsworld.com  March 03, 2020

Nature, vol.578, February 27, 2020