Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Physicists get a perfect material for air filters

02.03.2016

Physicists have created a perfect material for filters and respirators

A research team from the Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences have synthesized the material that is perfect for protection of respiratory organs, analytical research and other practical purposes.


A sample of the new fabric in reflected light.

Credit: The picture is courtesy of the researchers

An almost weightless fabric made of nylon nanofibers with a diameter less than 15 nm beats any other similar materials in terms of filtering and optical properties.

The scientists whose work is published in Macromolecular Nanotechnology Journal, characterize their material as lightweight (10-20 mg/m2), almost invisible (95% light transmission: more than that of a window glass), showing low resistance to airflow and efficient interception of <1 micrometer fine particulate matter.

The wording "nanofibers" in the researchers' article is more than a fashion statement. Previously, the same team demonstrated that reducing fiber diameter from 200 nanometers down to 20 decreased filter resistance to airflow by two thirds, and this effect could no longer be explained by classical aerodynamics.

When an obstacle size is smaller than the free path of gas molecules, the standard methods estimating aerodynamic resistance based on the continuum theory no longer work. In normal conditions, the mean free path of air molecules makes 65 nanometers.

The mean free path is the average distance one molecule manages to cover before colliding with another. Only if all obstacles are much bigger than this value, the free stream coming at them can be rightfully considered a continuous medium.

The scientists used the technique called electrospinning: a jet of a dissolved polymer is ejected through a special nozzle aiming at a target under action of an electric field. From the other side, ethanol is electrosprayed. The polymer jet and the alcohol ions take the opposite electric charges. Colliding in the air, they form ultra-thin fibrous films.

Electrospinning technology as a way to produce nonwoven fibrous filters has been developed back in the 50s to purify air in atomic industry. However, the researchers introduced an important improvement: instead of obtaining nanomats on a solid conducting substrate like before, now with the new technology, a free filter is formed covering a 55-mm hole in a non-conductive polycarbonate screen.

The published work completed the cycle of the authors' papers devoted to development of the manufacturing technology and studies of properties of nanofilters manufactured using this new process. It was established that the unique optical and filtering properties originate from a special mechanism of "healing" holes and defects in free standing filters. Such holes literally attract fibers landing onto the filter surface.

As a result, a good filter without big holes can be obtained from a minimum amount of nanofibers and, accordingly, with a minimum resistance to airflow. Moreover, active healing of big holes between threads provides the filters with the properties inherent in filters with calibrated pores, so called track-etched membranes (Nuclepores). The scientists have also demonstrated that the "healing" mechanism does not work in the conventional electrospinning technique where nanofibers are deposited onto a conducting substrate completely at random.

The testing of nylon-4,6 electrospun films showed that thess almost weightless and invisible fabrics trap no less than 98% of airborne dust particles. For testing, the scientists used particles from 0.2 to 0.3 micron in diameter. This roughly corresponds to the dust that is not caught by the nasal pharynx, and penetrates the lungs causing a number of dangerous medical conditions. Submicron particles (< 1 micrometer in diameter) are the ones also used to test industrial and medical filters. To assess performance, resistance to airflow is tested as well.

Experiments to measure resistance have been made on singular samples so far. In real filters a multi-layer surface with a complex configuration is normally used. The experiments showed that the nylon-4,6 filtering material had the best properties out of all types of fabric previously described . In terms of interception extent to filter weight ratio and interception-resistance to airflow ratio, the new filtering material beats any existing equivalents by several times.

At first it looks like a ring sitting on a sheet of paper. In reality, it is a sample of the new fabric for filters. The small red spot on top of "l" letter is a spot wherea laser beam penetrates the film. Low intensity of dispersed light demonstrates high transparency of the new material. A transmission index of the new product is higher than that of a good window glass. The picture is courtesy of the researchers.

Speaking about possible applications of this material, the scientists claim it is more than the obvious air and water purification from particulate matter. Since the material surpasses glass in transparency, it can be used in biological research. For example, after pumping air or water through the new filter intercepted microorganisms may be directly observed right on the transparent filter under a microscope. Again, this effect is due to ultra-fine threads. Their thickness is significantly less than even visible light wavelength.

Media Contact

Valerii Roizen
press@mipt.ru
7-929-992-2721

 @phystech

http://mipt.ru/en/ 

Valerii Roizen | EurekAlert!

Further reports about: airflow diameter glass healing material nanofibers nanometers physics weightless window glass

More articles from Materials Sciences:

nachricht Nanomaterial makes laser light more applicable
28.03.2017 | Christian-Albrechts-Universität zu Kiel

nachricht New value added to the ICSD (Inorganic Crystal Structure Database)
27.03.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Transport of molecular motors into cilia

28.03.2017 | Life Sciences

A novel hybrid UAV that may change the way people operate drones

28.03.2017 | Information Technology

NASA spacecraft investigate clues in radiation belts

28.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>