Microfluidically-Reconfigured Refractive Metasurface Antenna With Center Frequency and Beam-Steering Tuning Capabilities

In this article, a microfluidically-reconfigured metasurface (MSF) antenna with center frequency and beam-steering tuning capabilities is presented. Liquid metal ink (LMI) Galinstan is used to control the reflection and transmission phases of an MSF layer that is placed on top of a patch radiator. The MSF layer consists of a $6\times 6$ array, and it is placed directly under a 3-D-printed layer of polylactic acid (PLA) hosting seven microfluidic channels. The patch antenna can reconfigure its operating frequency from 4.7 to 5.5 GHz with the assistance of two 3-D-printed channels, hosting LMI, which can effectively modify the actual size of the patch radiator. The patch antenna and the suspended MSF top layer, form a Fabry–Perot cavity (FPC), which enhances the antenna gain. By selectively filling in the channels with LMI, beam-steering can be achieved. The maximum far-field gain of the antenna in the broadside direction is 12.5 dBi, and it remains greater than 9.5 dBi when the main beam is steered toward ±20°. To validate the simulated performance, the microfluidically-reconfigured MSF antenna was manufactured and tested for alternative tuning states. Specifically, when all seven channels are air-filled, a fractional bandwidth of 9% (4.99–5.47 GHz) with a high gain of 12.5 dBi was obtained. By filling with LMI three out of the seven parallel channels, the main lobe of the antenna can be steered by ±20°. In addition, the center frequency of the MSF antenna can be tuned between the continuous range of 4.55–5.50 GHz, based on the wide bandwidth of four distinct frequencies caused by the four possible combinations of two microfluidic channels, which are filled with either LMI or air.