Polymer film protects from electromagnetic radiation, signal interference

3 nanowires. Credit: Zahra Barani / UC Riverside “width =” 800 “height =” 530 “/>

As electronic devices reduce all areas of public and personal life, engineers are scrambling to find lightweight, mechanically stable, flexible and easy-to-manufacture materials that protect people from excess electromagnetic radiation. has prevented electronic devices from interfering with each other.

In a positive report published in Advanced materials– the leading journal in the field – engineers at the University of California, Riverside describe flexible film using a semi-automatic nanomaterial filler that combines an excellent electromagnetic shield with easy manufacturing.

“These novel films are promising for high-frequency communication technologies, which need to protect electromagnetic films that are flexible, lightweight, corrosion-resistant, inexpensive, and electronically insulated,” said lead author Alexander A Balandin, distinguished professor of electrical and computer engineering at Marlan UC Riverside and Rosemary Bourns College of Engineering. “They attach strongly to high-frequency radiofrequency radiation while maintaining electrical insulation in direct flow measurements. “

Electromagnetic interference, or EMI, occurs when signals from different electronic devices overlap, affecting performance. The signal from a cell phone or laptop WiFi, or even a kitchen combination, could cause static to appear on a TV screen, for example. Similarly, airlines require passengers to switch off cell phones when they land and remove them as their signals can interfere with navigation signals.

Engineers have long learned that any electrical device can affect the activity of a nearby machine and have developed materials to protect electronics from interfering with signals. But now that electronic devices have become ubiquitous, small, wirelessly connected, and essential to countless essential services, the opportunities for and risks associated with EMI misconduct have grown, and often do not. conventional EMI protection products are insufficient. More electronic devices mean that people are also exposed to more electromagnetic radiation than before. New protective materials will be needed for the next generation of electronics.

Balandin led a team that developed a scalable synthesis of compounds with non-conventional fillers – exfoliated chemical bags of van der Waals semi-solid materials. The composites showed EMI-specific protective materials in the gigahertz and sub-terahertz frequency ranges, important for current and future communications technologies, while still electronically insulated.

Graphene is the most famous van der Waals material. It is bilateral because it is a plane of strongly bound atoms. Many planes of graphene, with weak van der Waals forces, make up a large graphite crystal. For many years, research focused specifically on two-dimensional van der Waals materials, which extend to atomic planes.

3 nanowires. Cliu: Zahra Barani / UC Riverside “/>

In one-dimensional van der Waals materials atomic chains are tightly bound, rather than planes, which are weakly bound by van der Waals forces. Such materials exfoliate into needle-like “one-sided” structures rather than two-dimensional planes. The Balandin group conducted advanced studies of one-dimensional metals revealing their rare properties. In the new paper, the Balandin group reports the use of a chemical process that can be augmented for mass production of these unilateral products.

Doctoral student Zahra Barani and Fariboz Kargar, a research professor and project scientist with Balandin’s Optimized Phonon Engineered Materials, or POEM Center, combined the specific materials by the treatment of moving metal trichalcogenides, or TaSe₃, a van der Waals-coated material with a semi-one-dimensional crystal structure, with chemicals that have made the peeling of needle-like nan der-1D van der Waals with very large viewing ratios of up to ~ 106— well longer than thick. In a previous study, the group found that bags of quasi-1D TaSe₃ atomic fibers can support high-density densities.

“There was no standard recipe for exfoliation of these products. I did a lot of trial and error tests, while studying energy cleavage and other important parameters to produce them with high yield. I knew it was the key is to get bags with high aspect ratio As far as I can, as EM waves pair with longer and thinner strands.This required optical microscopy and scanning electron microscopy character after each step of exfoliation, “Barani first author said.

The researchers filled a matrix made of a special polymer with bags of the exfoliated TaSe₃ to make a thin, black film. The synthesized composite films, although still electrically insulated, showed exceptional performance in suppressing electromagnetic waves. The polymer composites with low loads of the fillers were particularly efficient.

“The electromagnetic shield efficiency of composites is related to the aspect ratio of the nets. The higher the side ratio, the lower the fill density required to provide an important EM shield,” Kargar said. “This is beneficial, because by reducing the content of the filler one would take advantage of the inherent properties of polymers such as light weight and flexibility. In this regard, I can say that this type of material is excellent once and that they are properly exfoliated, controlling the thickness and length. “

“Eventually, I got them right, prepared a gauge and measured the EMI properties. The results were amazing: the electrical conductivity was only more than 99.99% of the EMI shield for micrometer thick films,” said Barani.

The quasi-1D van der Waals metal fillings can be produced cheaply and in large quantities. Balandin said research on atomic bags of van der Waals quasi-1D materials as individual conductors, and assemblies with such materials are just beginning.

“I’m sure we’ll see a lot of progress soon with van der Waals quasi-1D products, as happened with semi-2-D products,” he said.