Liquid-based transparent, wideband and reconfigurable absorber/reflector

Abstract

In this paper, an optically transparent and wideband absorber/reflector with switchable states and tunable frequency spectrum is presented. The proposed structure consists of a Polydimethylsiloxane (PDMS) layer with microchannel structures and an Indium Tin Oxide (ITO) layer as the metal panel. The switching function is implemented by controlling the injection and discharge of pure water, and the switchable frequency band of the absorbing and reflecting states ranges from 7.9 to 34.4 GHz with a fractional bandwidth of 125.2%. The tunable properties are achieved by changing the concentration of the injected saline water. In addition, the distributions of the electric field, the magnetic field and the power loss density are used to further understand the physical mechanism of the structure. Moreover, it also performs well under different polarizations and incident angles. For validation, a transparent and wideband absorber/reflector is fabricated and tested, and the simulated and measured results are consistent with each other.

A multifunctional frequency selective rasorber based on hybrid microfluidic-electronic control

“…Based on the authors' previous research [34,36], the upper lossy layer of the FSR is designed by using water. The classic Debye model for the dielectric permittivity of pure water, including a dependance on the temperature, is employed in our analysis [37]:…”

“…The simulation results indicated that the absorptivity of the proposed absorber remained above 90% within the frequency range of 16.52-100.00 GHz. In addition, water has the unique advantage of liquidity in the design of reconfigurable metamaterial systems [25,26,[32][33][34][35][36]. In [32], a water-based reconfigurable FSR has been proposed for the first time, which consists of a 3D printed container and a bandpass FSS.…”

Design of a broadband multifunctional switchable absorber/reflector based on active frequency selective surfaces

“…Active absorbers based on FSS, which combine two different functions and can generally be switched primarily from the absorbing state to other states, are proposed to obtain dynamic characteristics. As of now, most scholars are working on three types of absorption switches: absorbers/reflectors [15][16][17][18][19][20][21], absorbers/ radiators [22], and absorbers/transmitters [23,24]. Among them, the switchable absorber/reflector integrating two opposite functions plays a vital role in military stealth, which can hide the object in a wide bandwidth to avoid detection by the enemy in the absorbing state and can declare itself by flashing periodically in the reflecting state.…”

Transparent and broadband switchable absorber/reflector based on structured water medium

“…Besides, owing to its frequency dispersion and large dielectric losses properties, water can be utilized as a kind of dielectric material to realize waterbased absorbers with efficient and broadband absorbing features [29][30][31][32][33][34][35][36][37]. By taking advantages of these physical and electrical properties of water simultaneously, some reconfigurable water-based absorbers with optical transparency and broadband properties are developed [38][39][40][41]. Zhang et al presented a transparent and broadband water-based absorber whose absorption bandwidth can be tuned by controlling the thickness of water substrate [38].…”

“…By controlling the injection of water into the fluidic channels, an optically transparent microwave surface for switchable absorption and reflection function has been proposed by Jeong et al recently, but a high modulation of the absorption and reflection performance in the entire operating band is still challenging, especially for the reflection properties [39]. Two broadband transparent absorber/reflector designs have been presented [40,41]. However, the structures are either based on standing-up water blocks or swastikashaped water structures, which are complex and put forward higher processing requirements.…”