( b) The incident phase calculation of the point source feed. ( a) The anomalous refraction under plane-wave incidence. The schematic of the presented reconfigurable metasurface antenna. We believe this work will stimulate more researches on reconfigurable and flexible designs utilizing liquid metal for diverse applications. The measured results have good agreement with the simulation, verifying our design. We designed several phase distributions on the surface to generate the scattering beam in different directions. By rotating and reconstructing the liquid metal shape, the reflected phase response of the element shows various distinct states, covering more than 270° phase range. A square-ring cavity structure has been designed, simulated and fabricated to demonstrate our design. To explore a flexible and low-cost reconfigurable method, here, we present a metasurface antenna based on liquid metal for flexible scattering fields manipulation. However, many of the researches we mentioned above need complex hardware system design, requiring active components like PIN diodes, switches, and varactors, demanding high control complexity and cost. Through the reconfigurable technologies, the performance of antenna can be transformed, such as the working frequency, polarization mode, radiation pattern and the combination of the above performance. There are three methods to realize reconfiguration of antenna: electronic device reconfiguration (such as pin diode, radio frequency (RF) switches, varactor diode, etc.), mechanical reconfiguration and changing the material properties of the antenna. The reconfiguration of antenna performance is realized by adjusting the state of controllable devices integrated in the general radiation aperture. In recent years, the concept of reconfigurable antenna has been proposed. Therefore, people continue to explore new concepts and technologies of various antennas to break through the related problems. It is expected that the antenna unit has the characteristics of a wide beam, wide frequency band and high gain. With the rapid development of wireless information technology, higher and higher requirements are put forward for the antenna system.
The antenna is an essential part of the wireless information system. At present, the tuning methods of reconfigurable metamaterials mainly include mechanical tuning, electronic tuning, material property tuning and optical tuning. Its rapid development makes it possible to manufacture metadevices with practical functions and unique subwavelength devices. Reconfigurable metamaterials are composed of passive metamaterials and active components. Due to the fact that metamaterials can be designed artificially, they can be widely used in a variety of applications, such as negative and zero refraction, perfect absorption, invisibility cloaking, dielectrics lenses and vortex beams. Metamaterials are three-dimensional artificial structures with special electromagnetic properties. The concept of metamaterials has attracted much attention in the past decade. The presented reconfigurable scheme may promote more interest in various antenna designs on 5G and intelligent applications. The experimental results have good consistency with the simulation design, which demonstrated our works. By arranging different metal structure distribution, we show that the scattering fields generated by the surface have diverse versions including single-beam, dual-beam, and so on. By melting and rotating the element structure, the shape of liquid metal can be altered, resulting in the distinct reflective phase responses. We have designed an element cavity structure to contain liquid metal for its flexible shape-reconstruction. Since the Eutectic gallium indium (EGaIn) liquid metal has a melting temperature around the general room temperature (about 30 ☌), the structure based on the liquid metal can be easily reconstructed under the temperature control. In this paper, we propose a reconfigurable metasurface antenna for flexible scattering field manipulation using liquid metal.