Microfluidically-Reconfigured Refractive Metasurface Antenna with Center Frequency and Beam-steering Tuning Capabilities

In this paper, 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 6x6 array, and it is placed directly under a 3D-printed layer of polylactic acid (PLA) hosting seven microfluidic channels. The patch antenna can reconfigure its operating frequency from 4.7 – 5.5 GHz with the assistance of two 3D-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 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 towards ±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°. Additionally, 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.