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Improving Stealth Technology

The field of stealth technology has gotten a boost from new research by scientists at Nanyang Technological University (NTU).
Scientists at the School of Electrical and Electronic Engineering (EEE), Centre for Bio Devices and Signal Analysis (VALENS), led by Professor Liu Ai Qun have developed a new liquid-metal-based metasurface absorption material with broadband tunability and wide-angle features. The material could improve terahertz wave shielding and stealth technology.
While scientists elsewhere have created other terahertz metasurface absorption materials, most of these suffer from a limited tuning range and narrow incident angle.
Even when much effort has been devoted to making wide-angle absorption materials, these have been effective only within a restricted frequency range.   
The EEE researchers’ proof-of-principle material uses a liquid-metal pillar array that can be continuously controlled in the vertical direction using microfluidic technology. A U-shaped resonator is filled with liquid metal, in this case mercury, to form the liquid-metal pillars.  
By applying different air pressures to the resonator, the pillars’ height can be increased or decreased to between 0 and 100 micrometres. 
For their experiments, the EEE team used four of the pillars sandwiched between two polydimethylsiloxane layers as one element. This element was then patterned periodically into a square array. 
By controlling the height of the pillars, the absorption frequency of the metasurface can be tuned from 0.246 terahertz to 0.415 terahertz with a tuning range of central frequency 51.1 percent and absorbance of more than 90 percent.
When the incident angle is increased from 0 degrees to 60 degrees, the tuning range of central frequency of the absorption peak covers 27.6 percent from 0.25 terahertz to 0.33 terahertz, with absorbance of more than 90 percent.
While the researchers used mercury, the liquid metal can be replaced by other such metals, including galinstan and liquid phase conducting polymers. 
“Our frequency-agile and wide-angle terahertz absorption material has potential applications in terahertz wave shielding, stealth technology and more,” said Professor Liu.
By Professor Liu Ai Qun
Click here to find out more.
Published on: 28 December-2017 ​​​​​​​​
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