Large-scale fluidic tuning of sub-wavelength periodic structures

In this paper, we present a technique to fluidically tune the response of periodic structures composed of sub-wavelength constituting unit cells. This technique is applied to a two-dimensional periodic structure with multiple unit cells and the response of the structure is continuously tuned over a broad frequency band. The technique is based on embedding metal and glass balls inside several parallel channels within the dielectric substrate which supports the periodic structure. In each channel, a periodic arrangement of metal and glass balls is assembled and is allowed to move freely within the channel. By moving this periodic train of balls over small distances with respect to the fixed periodic structure, the response of the structure is continuously tuned. 3D printing technology is used to implement the dielectric substrate with embedded fluidic channels. The structure is designed to ensure that the movement of balls in all channels can be synchronized. A prototype with 8 parallel channels accommodating 9 unit cells in each channel is fabricated using a Viper Si2 3D printer and synchronization movement of the balls is verified experimentally when the balls in channels are embedded in mineral oil and pressure driven. Then a prototype with 16 channels is designed to experimentally verify the synchronous movement of balls and the tuning range achievable from the prototype.