Engineering news
The thin film device could adjust the performance of electronic devices, strengthen wireless connections and secure mobile communications against intrusion, said the researchers at Drexel University in Pennsylvania.
Led by Professor Yury Gogotsi, the team previously demonstrated that 2D materials called MXenes can be turned into an active shield against electromagnetic waves when combined with an electrolyte solution.
The team’s latest work shows how the shielding can be ‘tuned’ when a small voltage – less than that produced by an alkaline battery – is applied.
“Dynamic control of electromagnetic wave jamming has been a significant technological challenge for protecting electronic devices working at gigahertz frequencies and a variety of other communications technologies,” Gogotsi said.
“As the number of wireless devices being used in industrial and private sectors has increased by orders of magnitude over the past decade, the urgency of this challenge has grown accordingly. This is why our discovery – which would dynamically mitigate the effect of electromagnetic interference on these devices – could have a broad impact.”
MXene is highly conductive, making it perfectly suited for reflecting microwave radiation that could cause static, feedback or diminish the performance of communications devices. Its internal chemical structure can also be temporarily altered to allow these electromagnetic waves to pass through.
This means that a thin coating on a device or electrical component can prevent them from emitting electromagnetic waves and being penetrated by those emitted by other electronics. Eliminating interference from both internal and external sources can ensure the performance of a device, but some waves must be allowed to exit and enter when it is being used for communication.
“Without being able to control the ebb and flow of electromagnetic waves within and around a device, it’s a bit like a leaky faucet – you’re not really turning off the water and that constant dripping is no good,” Gogotsi said. “Our shielding ensures the plumbing is tight, so to speak – no electromagnetic radiation is leaking out or getting in until we want to use the device.”
The key to the ‘bidirectional tunability’ of MXene’s shielding property is using the flow and expulsion of ions to alternately expand and compress the space between the material’s layers, as well as to change the surface chemistry.
With a small voltage applied to the film, ions enter – or intercalate – between the MXene layers, altering the charge of their surface and inducing electrostatic attraction. This changes the layer spacing, conductivity and shielding efficiency of the material. When the ions are deintercalated, as the current is switched off, the MXene layers return to their original state.
The team tested 10 different MXene-electrolyte combinations, applying each via paint sprayer in a layer about 30- to 100-times thinner than a human hair. The materials consistently demonstrated dynamic tunability of shielding efficiency in blocking microwave radiation, which is impossible for traditional metals like copper and steel. The device sustained the performance through more than 500 charge-discharge cycles.
For security applications, Gogotsi suggested that the MXene shielding could hide devices from detection by radar or other tracing systems. The team also tested the potential of a one-way shielding switch, which would allow a device to remain undetectable and protected from unauthorised access until it is deployed for use.
“A one-way switch could open the protection and allow a signal to be sent or communication to be opened in an emergency or at the required moment,” Gogotsi said. “This means it could protect communications equipment from being influenced or tampered with until it is in use. For example, it could encase the device during transportation or storage and then activate only when it is ready to be used.”
The team will now explore additional MXene-electrolyte combinations and mechanisms to fine-tune the shielding, potentially enabling dynamic adjustments to block radiation at a variety of bandwidths.
The research was reported in Nature Nanotechnology.
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